Thursday, August 30, 2012

How to build Op-Amp Booster Designs - PDF

Description

Although modern integrated circuit operational amplifiers ease linear circuit design, IC processing limits amplifier output power. Many applications, however, require substantially greater output voltage swing or current (or both) than IC amplifiers can deliver. In these situations an output “booster,” or post amplifier, is required to achieve the needed voltage or current gain. Normally, this stage is placed within the feedback loop of the operational amplifier so that the low drift and stable gain characteristics of the amplifier are retained.
Op-Amp Booster Designs - PDF
Because the booster is a gain stage with its own inherent AC characteristics, the issues of phase shift, oscillation, and frequency response cannot be ignored if the booster and amplifier are to work well together. The design of booster stages which achieve power gain while maintaining good dynamic performance is a difficult challenge. The circuitry for boosters will change with the application’s requirements,which can be very diverse.

This application note explains the following designs with diagrams and definitions.

  1. 200 mA Current Booster
  2. Ultra High Speed Fed-Forward Current Booster
  3. Voltage-Current Booster
  4. ±120V Swing Booster
  5. High Current Booster
  6. Indestructible, Floating Output Booster
  7. 1000V-300 mA Booster
  8. 300V Output Booster
Source: http://www.hqew.net/circuit-diagram/How-to-build-Op$2dAmp-Booster-Designs-$2d-PDF_6279.html

How to build Mains Supply Failure Alarm

Description

Whenever AC mains supply fails, this circuit alerts you by sounding an alarm. It also provides a backup light to help you find your way to the torch or the generator key in the dark. The circuit is powered directly by a 9V PP3/6F22 compact battery. Pressing of switch S1 provides the 9V power supply to the circuit. A red LED (LED2), in conjunction with zener diode ZD1 (6V), is used to indicate the battery power level.
Resistor R9 limits the operating current (and hence the brightness) of LED2. When the battery voltage is 9V, LED2 glows with full intensity. As the battery voltage goes below 8V, the intensity of LED2 decreases and it glows very dimly. LED2 goes off when the battery voltage goes below 7.5V. Initially, in standby state, both the LEDs are off and the buzzer does not sound. The 230V AC mains is directly fed to mains-voltage detection optocoupler IC MCT2E (IC1) via resistors R1, R2 and R3, bridge rectifier BR1 and capacitor C1.
Illumination of the LED inside optocoupler IC1 activates its internal phototransistor and clock input pin 12 of IC2 (connected to 9V via N/C contact of relay RL1) is pulled low. Note that only one monostable of dual-monostable multivibrator IC CD4538 (IC2) is used here. When mains goes off, IC2 is triggered after a short duration determined by components C1, R4 and C3. Output pin 10 of IC2 goes high to forward bias relay driver transistor T1 via resistor R7.

Circuit diagram:

Mains Supply Failure Alarm-Circuit diagram
Relay RL1 energises to activate the piezo buzzer via its N/O contact for the time-out period of the monostable multivibrator (approximately 17 minutes). At the same time, the N/C contact removes the positive supply to resistor R4. The time-out period of the monostable multivibrator is determined by R5 and C2. Simultaneously, output pin 9 of IC2 goes low and pnp transistor T2 gets forward biased to light up the white LED (LED1).
Light provided by this back-up LED is sufficient to search the torch or generator key. During the mono time-out period, the circuit can be switched off by opening switch S1. The ‘on’ period of the monostable multivibrator may be changed by changing the value of resistor R5 or capacitor C2. If mains doesn’t resume when the ‘on’ period of the monostable lapses, the timer is retriggered after a short delay determined by resistor R4 and C3.





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How to build Fridge Door Alarm Circuit

Description

This circuit, enclosed into a small box, is placed in the fridge near the lamp (if any) or the opening. With the door closed the interior of the fridge is in the dark, the photo resistor R2 presents a high resistance (up to 200K) thus clamping IC1 by holding pin 12 high. When a beam of light enters from the opening, or the fridge lamp illuminates, the photo resistor lowers its resistance (less 2K), pin 12 goes low, IC1 starts counting and, after a preset delay (20 seconds in this case) the piezo sounder beeps for 20 sec. then stops for the same lapse of time and the cycle repeats until the fridge door closes. D2 connected to pin 6 of IC1 allows the piezo sounder beeping 3 times per second.

Circuit diagram:

Fridge Door Alarm Circuit-Circuit diagram

Parts:

  • R1 = 10K
  • R2 = LDR
  • R3 = 100K
  • R4 = 100K
  • D1 = 1N4148
  • D2 = 1N4148
  • Q1 = BC337
  • C1 = 10nF-63V
  • C2 = 100uF-25V
  • B1 = 3V Battery
  • IC1 = 4060 Ripple Counter & Oscillator IC
  • BZ1 = Piezo Buzzer Incorporating 3KHZ Oscillator
  • SW1 = Miniature SPST Slider Switch

Notes:

  • Connecting D1 to pin 2 of IC1 will halve the delay time.
  • Delay time can be varied changing C1 and/or R3 values.
  • Any photo resistor type should work.
  • Quiescent current drawing is negligible, so SW1 can be omitted.
  • Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture.
  • Do not put this device in the freezer.


Source: http://www.hqew.net/circuit-diagram/How-to-build-Fridge-Door-Alarm-Circuit_6273.html

How to build Fridge Door Alarm Schematic 2nd Version

Description

The main purpose of this design was to obviate a small defect of the very popular Fridge Door Alarm circuit, available on this website since 1999 and built by a lot of hobbyists. Unfortunately, that circuit stops operating when the battery voltage falls below about 2.6 - 2.7 Volts. This is due to the 4060 CMos IC used. In some cases, devices made by some manufacturers (but not Motorola's) fail to operate even at nominal 3V supply voltage.
A simple cure to this shortcoming could be the substitution of the original IC specified with a 74HC4060 chip: this should allow circuit operation down to 2V but, unfortunately, this IC is not easy to locate. For this reason, an equivalent circuit using about the same parts counting was developed, in order to allow safe operation even when battery voltage falls down to about 1.3V.

Circuit operation:

The circuit, enclosed in a small box, should be placed in the fridge near the lamp (if any) or close to the opening. With the door closed, the interior of the fridge is in dark, the photo resistor R2 presents a high resistance (>200K) thus clamping IC1 by holding C1 fully charged across R1 and D1. When a beam of light enters from the opening, or the fridge lamp lights, the photo resistor lowers its resistance (<2K) stopping C1 charging current.
Therefore IC1, wired as an astable multivibrator, starts oscillating at a very low frequency and after a period of about 24 sec. its output pin (#3) goes high, enabling IC2. This chip is also wired as an astable multivibrator, driving the Piezo sounder intermittently at about 5 times per second. The alarm is activated for about 17 sec. then stopped for the same time period and the cycle repeats until the fridge door closes.

Circuit diagram:

Fridge Door Alarm Schematic 2nd Version-Circuit diagram

Parts:

  • R1 = 10K - 1/4W Resistor
  • R2 = Photo resistor (any type)
  • R3 = 2.2M - 1/4W Resistor
  • R4 = 1M - 1/4W Resistor
  • C1 = 10μF - 25V Electrolytic Capacitor
  • C2 = 100nF - 63V Polyester Capacitor
  • D1 = 1N4148 - 75V 150mA Diode
  • IC1 = 7555 or TS555CN CMos Timer IC
  • IC2 = 7555 or TS555CN CMos Timer IC
  • BZ1 = Piezo sounder (incorporating 3KHz oscillator)
  • B1 = 3V Battery (2 x 1.5V AA, AAA or smaller type Cells in series)

Notes:

  • Delay time can be varied changing C1 and/or R3 values.
  • Beeper repetition rate can be varied changing C2 and/or R4 values.
  • Stand-by current drawing: 150μA.
  • Place the circuit near the lamp and take it away when defrosting, to avoid circuit damage due to excessive moisture.
  • Do not put this device in the freezer.
The article comes from http://www.hqew.net/circuit-diagram/How-to-build-Fridge-Door-Alarm-Schematic-2nd-Version_6274.html

Wednesday, August 29, 2012

How to build Two-Led Pilot Light


Description

This circuit is designed on request and can be useful to those whishing to have, say, a red LED illuminated when an appliance is on and a green LED illuminated when the same appliance is off. Any mains operated appliance can be monitored by this circuit provided a suitable mains switch, capable of withstanding the full load current, is used for SW1.When SW1 is closed, the load and D4 are energized, Q1 is saturated and shorts D3, thus preventing its illumination.

Circuit Diagram:

Two-Led Pilot Light-Circuit Diagram

Parts:

  • R1 = 27K-1W
  • R2 = 27K-1W
  • R3 = 6.8K
  • D1 = 1N4007
  • D2 = 1N4007
  • D3 = Green
  • D4 = Red Led
  • Q1 = BC337
  • SW1 = SPST Mains Switch

Notes:

  • Change R1 and R2 to 15K 1W for 115Vac mains operation.
  • SW1 must be capable of withstanding the appliance's full load current and voltage.







    Reprinted Url Of This Article:http://www.hqew.net/circuit-diagram/How-to-build-Two$2dLed-Pilot-Light_6252.html

    How to build Digital Step-Km Counter Circuit Schematic


    Description

    This circuit measures the distance covered during a walk. Hardware is located in a small box slipped in pants' pocket and the display is conceived in the following manner: the leftmost display D2 (the most significant digit) shows 0 to 9 Km. and its dot is always on to separate Km. from hm. The rightmost display D1 (the least significant digit) shows hundreds meters and its dot illuminates after every 50 meters of walking.
    A beeper (excludable), signals each count unit, occurring every two steps. A normal step was calculated to span around 78 centimeters, thus the LED signaling 50 meters illuminates after 64 steps (or 32 operations of the mercury switch), the display indicates 100 meters after 128 steps and so on.
    For low battery consumption the display illuminates only on request, pushing on P2. Accidental reset of the counters is avoided because to reset the circuit both pushbuttons must be operated together. Obviously, this is not a precision meter, but its approximation degree was found good for this kind of device. In any case, the most critical thing to do is the correct placement of the mercury switch inside of the box and the setting of its sloping degree.

    Circuit diagram:

    Digital Step-Km Counter Circuit Schematic-Circuit diagram

    Parts:

    • R1 = 22K 1/4W Resistor
    • R2 = 2.2M 1/4W Resistor
    • R3 = 22K 1/4W Resistor
    • R4 = 1M 1/4W Resistor
    • R5 = 4.7K 1/4W Resistor
    • R6 = 47R 1/4W Resistor
    • R7 = 4.7K 1/4W Resistor
    • R8 = 4.7K 1/4W Resistor
    • R9 = 1K 1/4W Resistor
    • C1 = 47nF 63V Polyester Capacitor
    • C2 = 100nF 63V Polyester Capacitor
    • C3 = 10nF 63V Polyester Capacitor
    • C4 = 10μF 25V Electrolytic Capacitor
    • D1 = Common-cathode 7-segment LED mini-display (Hundreds meters)
    • D2 = Common-cathode 7-segment LED mini-display (Kilometers)
    • Q1 = BC327 45V 800mA PNP Transistors
    • Q2 = BC327 45V 800mA PNP Transistors
    • P1 = SPST Pushbutton (Reset)
    • P2 = SPST Pushbutton (Display)
    • IC1 = 4093 Quad 2 input Schmitt NAND Gate IC
    • IC2 = 4024 7 stage ripple counter IC
    • IC3 = 4026 Decade counter with decoded 7-segment display outputs IC
    • IC4 = 4026 Decade counter with decoded 7-segment display outputs IC
    • SW1 = SPST Mercury Switch, called also Tilt Switch
    • SW2 = SPST Slider Switch (Sound on-off)
    • SW3 = SPST Slider Switch (Power on-off)
    • BZ = Piezo sounder
    • B1 = 3V Battery (2 AA 1.5V Cells in series)

    Circuit operation:

    IC 1A & IC 1B form a monostable multi vibrator providing some degree of freedom from excessive bouncing of the mercury switch. Therefore a clean square pulse enters IC2 that divides by 64. Q2 drives the LED dot-segment of D1 every 32 pulses counted by IC2. Either IC3 & IC4 divide by 10 and drive the displays. P1 resets the counters and P2 enables the displays. IC1C generates an audio frequency square wave that is enabled for a short time at each monostable count. Q1 drives the piezo sounder and SW2 allows disabling the beep.

    Notes:

    • Experiment with placement and sloping degree of mercury switch inside the box: this is very critical.
    • Try to obtain a pulse every two walking steps. Listening to the beeper is extremely useful during setup.
    • Trim R6 value to change beeper sound power.
    • Push P1 and P2 to reset.
    • This circuit is primarily intended for walking purposes. For jogging, further great care must be used with mercury switch placement to avoid undesired counts.
    • When the display is disabled current consumption is negligible, therefore SW3 can be omitted.

    Source: http://www.hqew.net/circuit-diagram/How-to-build-Digital-Step$2dKm-Counter-Circuit-Schematic_6254.html

    How to build On-off Infrared Remote Control


    Description

    Most homes today have at least a few infrared remote controls, whether they be for the television, the video recorder, the stereo, etc. Despite that fact, who among us has not cursed the light that remained lit after we just sat down in a comfortable chair to watch a good film? This project proposes to solve that problem thanks to its original approach. In fact, it is for a common on/off switch for infrared remote controls, but what differentiates it from the commercial products is the fact that it is capable of working with any remote control.
    Therefore, the first one you find allows you to turn off the light and enjoy your movie in the best possible conditions. The infrared receiver part of our project is entrusted to an integrated receiver (Sony SBX 1620-52) which has the advantage of costing less than the components required to make the same function. After being inverted by T1, the pulses delivered by this receiver trigger IC2a, which is nothing other than a D flip-flop configured in monostable mode by feeding back its output Q on its reset input via R4 and C3. The pulse that is produced on the output Q of IC.2A makes IC.2B change state, which has the effect of turning on or turning off the LED contained in IC3.

    Circuit diagram:

    On-off Infrared Remote Control-Circuit diagram
    This circuit is an opto triac with zero-crossing detection which allows our setup to accomplish switching without noise. It actually triggers the triac T2 in the anode where the load to be controlled is found. The selected model allows us to switch up to 3 amperes but nothing should stop you from using a more powerful triac if this model turns out to be insufficient for your use. In order to reduce its size and total cost, the circuit is powered directly from the mains using capacitor C5 which must be a class X or X2 model rated at 230 volts AC.
    This type of capacitor, called ‘self-healing’, is the only type we should use today for power supplies that are connected to ground. ‘Traditional’ capacitors, rated at 400 volts, do not really have sufficient safety guarantees in this area. Considering the fact that the setup is connected directly to the mains, it must be mounted in a completely insulated housing. A power outlet model works very well and can easily be used to inter-space between the grounded wall outlet and that of the remote control device.
    Based on this principle, this setup reacts to any infrared signal and, as we said before, this makes it compatible with any remote control. On the other hand, it has a small disadvantage which is that sometimes it might react to the ‘normal’ utilization of one of these, which could be undesirable. To avoid that, we advise you to mask the infrared receiver window as much as possible so that it is necessary to point the remote control in its direction in order to activate it.


    Reprinted Url Of This Article:

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    Tuesday, August 28, 2012

    How to build Simple Universal PIC Programmer

    Circuit diagram:

    Simple Universal PIC Programmer-Circuit diagram

    Description

    This simple programmer will accept any device that's supported by software (eg, IC-Prog 1.05 by Bonny Gijzen at www.ic-prog.com). The circuit is based in part on the ISP header described in the SILICON CHIP "PIC Testbed" project but also features an external programming voltage supply for laptops and for other situations where the voltage present on the RS232 port is insufficient. This is done using 3-terminal regulators REG1 & REG2. The PIC to be programmed can be mounted on a protoboard. This makes complex socket wiring to support multiple devices unnecessary. 16F84A, 12C509, 16C765 and other devices have all been used successfully with this device.



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    How to build When The Siren Sounds

    Description

    In Greek mythology, a siren was a demonic being (half bird, half woman). Later on this idea was transformed in art into a mermaid: a combination of a fish and a woman. Mechanical and electromechanical versions were invented even later, and electronic models were developed in the last century. Sirens are characterized by their ability to produce sounds that attract attention. With the exception of the flesh-and-blood models, they are thus used to warn people in a particular area of impending danger. The electronic versions are the most suitable for DIY construction.

    Circuit diagram:

    When The Siren Sounds-Circuit diagram
    There are lots of different ways to make an electronic siren. Here we use a binary counter (IC1) and an analogue multiplexer (IC2, which is a digitally configurable switch). The counter is a type 4060 IC, which has an integrated oscillator. The oscillator generates the tone of the siren. The frequency of this tone depends on the resistance between pin 10 of IC1 and the junction of C1 and R9. The trick here is that the analogue multiplexer adjusts the clock rate of the counter depending on the state of the counter.
    The frequency of the oscillator decreases as the resistance between pin 10 of IC1 and the junction of C1 and R9 increases, and the lower the frequency of the oscillator, the longer the counter remains in its current state. This means that high frequencies present on pin 9 are generated for shorter times than low frequencies. The values of resistors R1–R8 increase in uniform steps of approximately 10kO, with the result that the output on pin 9 is a series of eight decreasing frequencies, and this series is constantly repeated in cyclical fashion. Transistor T1 (BD139) and resistor R10 are included to boost the signal from pin 9 to a level suitable for driving a loudspeaker.
    The sound produced by this circuit may be familiar to some of our readers (especially if their memories extend back to older types of pinball and arcade game machines). You can also adjust the characteristics of the sound, since this circuit is primarily an invitation to experiment with the component values – in particular R1–R8 (10 k? minimum), but also C1. The values of R1–R8 do not have to follow a strictly increasing series; they can also be selected randomly. The current consumption is primarily determined by resistor R10 and the loudspeaker (in our case an 8-O type). The siren circuit draws approximately 33 mA at a supply voltage of 9 V. The supply current is 11 mA at the minimum supply voltage of 4 V, and it increases to 60 mA at the maximum supply voltage of 15 V.







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    How to build Music Generator Schematic Using UM66

    Description

    UM66 is a pleasing music generator IC which works on a supply voltage of 3V. the required 3V supply is given through a zener regulator. its out put is taken from the pin no1 and is given to a push pull amplifier to drive the low impedance loud speaker. A class A amplifier before push pull amplifier can be used to decrees the noise and improve out put. UM66 is a 3 pin IC package just looks like a BC 547 transistor.

    Circuit diagram:

    Music Generator Schematic Using UM66-Circuit diagram

    Parts:

    • R1 = 4.7K
    • C1 = 10uF-25v
    • D1 = 3.3v Zener
    • Q1 = SK100
    • Q2 = SL100
    • IC = UM66
    • SP = 8 ohm

    Pin out of UM66 IC:

    • Output----Melody Output
    • Vdd-----Positive power supply
    • -Vss------Negative Power supply

    Features of UM66T series:

    • 62 Note ROM Memory
    • Voltage rating: 1.3V to 3.3 V
    • Power on reset







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    How to build Simple White Noise Generator

    Description

    This two-transistor white noise generator has a surprising feature – about 30dB more noise than the more traditional designs. Q1 and Q2 can be any small-signal transistors with a beta of up to 400. The reverse-biased emitter-base junction of Q1 provides the noise source, which is fed into the base of Q2. Q2 forms a simple amplifier with a gain of 45dB. The improved output level is due mainly to the inclusion of C1, which provides a low-impedance AC source to the noise source while not disturbing the DC bias of Q1.

    Circuit diagram:

    Simple White Noise Generator-Circuit diagram
    The low amount of feedback also makes this circuit very resistant to oscillations and tolerant to circuit layout. Unfortunately, the truism of "no such thing as free lunch" also applies; C1 makes the circuit very sensitive to power supply ripple.





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    Monday, August 27, 2012

    How to build 220vAC Operated Remote Tester

    Description

    Here is a simple tester for checking the basic operations of an infrared remote control unit. It is low-cost and easy to construct. The tester is built around infrared receiver module TSOP1738. Operation of the remote control is acknowledged by a tone from the buzzer. The circuit is sensitive and has a range of approximately five meters. The integrated IR receiver detects, amplifies and demodulates IR signals from the remote control unit. The piezo buzzer connected at its output sounds to indicate the presence of signal from the remote control unit.

    Circuit Diagram:

    220vAC Operated Remote Tester-Circuit Diagram

    Parts:

    • R1 = 100R-1/2W
    • R2 = 47K
    • R3 = 47K
    • R4 = 100R-1/2W
    • C1 = 0.47uF-275V
    • C2 = 470uF-35V
    • C3 = 10uF-25V
    • D1 = 1N4007
    • D2 = 1N4007
    • D3 = TL431
    • B1 = Piezo Buzzer
    • IR1 = TSOP1738

    Circuit Operation:

    As shown in diagram output pin 3 of IR receiver module TSOP1738 (IR1) normally remains high and the B1 is in silent mode. When the IR receives an infrared signal, its output goes low and, as a result, the B1 sounds to indicate the reception of signal from the remote (such as TV remote control unit). Assemble the circuit on a general-purpose PCB and enclose in a cabinet. Make sure that the IR receiver module is placed on the front panel of the cabinet so that it can receive the IR signals easily. Before soldering/connecting the shunt regulator and IR module, refer for the pin configuration.



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    How to build 220vAC Operated Remote Tester

    Description

    Here is a simple tester for checking the basic operations of an infrared remote control unit. It is low-cost and easy to construct. The tester is built around infrared receiver module TSOP1738. Operation of the remote control is acknowledged by a tone from the buzzer. The circuit is sensitive and has a range of approximately five meters. The integrated IR receiver detects, amplifies and demodulates IR signals from the remote control unit. The piezo buzzer connected at its output sounds to indicate the presence of signal from the remote control unit.

    Circuit Diagram:

    220vAC Operated Remote Tester-Circuit Diagram

    Parts:

    • R1 = 100R-1/2W
    • R2 = 47K
    • R3 = 47K
    • R4 = 100R-1/2W
    • C1 = 0.47uF-275V
    • C2 = 470uF-35V
    • C3 = 10uF-25V
    • D1 = 1N4007
    • D2 = 1N4007
    • D3 = TL431
    • B1 = Piezo Buzzer
    • IR1 = TSOP1738

    Circuit Operation:

    As shown in diagram output pin 3 of IR receiver module TSOP1738 (IR1) normally remains high and the B1 is in silent mode. When the IR receives an infrared signal, its output goes low and, as a result, the B1 sounds to indicate the reception of signal from the remote (such as TV remote control unit). Assemble the circuit on a general-purpose PCB and enclose in a cabinet. Make sure that the IR receiver module is placed on the front panel of the cabinet so that it can receive the IR signals easily. Before soldering/connecting the shunt regulator and IR module, refer for the pin configuration.



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    How to build Usb Power Socket With Indicator

    Description

    Today, almost all computers contain logic blocks for implementing a USB port. A USB port, in practice, is capable of delivering more than 100 mA of continuous current at 5V to the peripherals that are connected to the bus. So a USB port can be used, without any trouble, for powering 5V DC operated tiny electronic gadgets. Nowadays, many handheld devices (for instance, portable reading lamps) utilise this facility of the USB port to recharge their built-in battery pack with the help of an internal circuitry.

    Circuit diagram:

    Usb Power Socket With Indicator-Circuit diagram
    Usually 5V DC, 100mA current is required to satisfy the input power demand. Fig. 1 shows the circuit of a versatile USB power socket that safely converts the 12V battery voltage into stable 5V. This circuit makes it possible to power/recharge any USB power-operated device, using in-dash board cigar lighter socket of your car. The DC supply available from the cigar lighter socket is fed to an adjustable, three-pin regulator LM317L (IC1). Capacitor C1 buffers any disorder in the input supply.
    Usb Power Socket With Indicator
    Resistors R1 and R2 regulate the output of IC1 to steady 5V, which is available at the ‘A’ type female USB socket. Red LED1 indicates the output status and zener diode ZD1 acts as a protector against high voltage. Assemble the circuit on a general-purpose PCB and enclose in a slim plastic cabinet along with the indicator and USB socket. While wiring the USB outlet, ensure correct polarity of the supply. For interconnection between the cigar plug pin and the device, use a long coil cord as shown in Fig. 2. Pin configuration of LM317L is shown in Fig. 3.







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    How to build A Tan Timer Circuit Diagram

    Description

    This timer was designed for people wanting to get tanned but at the same time wishing to avoid an excessive exposure to sunlight. A Rotary Switch sets the timer according to six classified Photo-types (see table). A Photo resistor extends the preset time value according to sunlight brightness (see table). When preset time ends, the beeper emits an intermittent signal and, to stop it, a complete switch-off of the circuit via SW2 is necessary.

    Circuit diagram:

    A Tan Timer Circuit Diagram-Circuit diagram

    Parts:

    • R1 = 47K - 1/4W Resistor
    • R2 = 1M - 1/4W Resistor
    • R3 = 120K - 1/4W Resistors
    • R4 = Photo resistor (any type)
    • R5 = 120K - 1/4W Resistors
    • C1 = 10μF - 25V Electrolytic Capacitors
    • C2 = 220nF - 63V Polyester Capacitor
    • C3 = 10μF - 25V Electrolytic Capacitors
    • D1 = 1N4148 - 75V 150mA Diodes
    • D2 = 1N4148 - 75V 150mA Diodes
    • Q1 = BC337 - 45V 800mA NPN Transistor
    • B1 = 3V Battery (two 1.5V AA or AAA cells in series)
    • IC1 = 4060 - 14 stage ripple counter and oscillator IC
    • IC2 = 4017 - Decade counter with 10 decoded outputs IC
    • SW1 = 2 poles 6 ways Rotary Switch (see notes)
    • SW2 = SPST Slider Switch
    • BZ1 = Piezo sounder (incorporating 3KHz oscillator)

    Notes:

    • Needing only one time set suitable for your own skin type, the rotary switch can be replaced by hard-wired links.
    • A DIP-Switch can be used in place of the rotary type. Please pay attention to use only one switch at a time when the device is off, or the ICs could be damaged.




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    Sunday, August 26, 2012

    How to build Bicycle Back Safety Light Circuit Schematic

    Description

    This circuit has been designed to provide a clearly visible light, formed by 13 high efficiency flashing LEDs arranged in a pseudo-rotating order. Due to low voltage, low drain battery operation and small size, the device is suitable for mounting on bicycles as a back light, or to put on by jogger/walkers. IC1 is a CMos version of the 555 IC wired as an astable multivibrator generating a 50% duty-cycle square wave at about 4Hz frequency.
    At 3V supply, 555 output (pin 3) sinking current operation is far better than sourcing, then LEDs D1-D6 are connected to the positive supply rail. In order to obtain an alternate flashing operation, a second 555 IC is provided, acting as a trigger plus inverter and driving LEDs D7-D12. D13 is permanently on. The LEDs are arranged in a two series display as shown below, with a center LED permanently on. This arrangement and the alternate flashing of the two series of LEDs provide a pseudo-rotating appearance.

    Circuit diagram:

    Bicycle Back Safety Light Circuit Schematic-Circuit diagram:

    Parts:

    • R1 = 10K
    • R2 = 100K
    • R3 = 10R
    • R4 = 10R
    • R5 = 10R
    • R6 = 10R
    • R7 = 10R
    • R8 = 10R
    • R9 = 100K
    • R10 = 100K
    • R11 = 10R
    • R16 = 10R
    • R17 = 150R
    • C1 = 1μF-63V
    • C2 = 10nF-63V
    • C3 = 100μF-25V
    • B1 = 3V Battery (2 AA 1.5V Cells in series)
    • SW1 = SPST Slider Switch
    • D1-D13 = Red LEDs 5mm. or bigger, high efficiency
    • IC1-IC2 = 7555 or TS555CN CMos Timer IC

    LED arrangement:

    Bicycle Back Safety Light Circuit Schematic-LED arrangement

    Notes:

    • Flashing frequency can be varied changing C1 value.
    • High efficiency LEDs are essential.





    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Bicycle-Back-Safety-Light-Circuit-Schematic_6166.html

    How to build Water Level Indicator Circuit Schematic

    Description

    The whole project was developed on a friend's request. Its purpose was to remotely monitor the water-level in a metal tank located in the attic by means of a very simple control unit placed in the kitchen, some floors below. Mains requirements were:
    1. No separate supply for the remote circuit
    2. Main and remote units connected by a thin two-wire cable
    3. Simple LED display for the main unit
    4. Battery operation to avoid problems related to mains supply and water proximity
    5. As the circuit was battery operated a low current consumption was obviously welcomed
    The very small remote unit is placed near the tank and measures the water level in three ranges by means of two steel rods. Each range will cover one third of the tank capacity:
    • Almost empty - signaled by means of a red LED (D3) in the control unit display
    • About half-level - signaled by means of a yellow LED (D2) in the control unit display
    • Almost full - signaled by means of a green LED (D1) in the control unit display

    Circuit diagram:

    Water Level Indicator Circuit Schematic-Circuit diagram

    Circuit operation:

    When the water-level is below the steel rods, no contact is occurring from the metal can and the rods, which are supported by a small insulated (wooden) board. The small circuit built around IC1 draws no current and therefore no voltage drop is generated across R5. IC2A, IC2B and Q1 are wired as a window comparator and, as there is zero voltage at input pins #2 and #5, D3 will illuminate. When the water comes in contact with the first rod, pin #13 of IC1 will go high, as its input pins #9 to #12 were shorted to negative by means of the water contact.
    Therefore, R4 will be connected across the full supply voltage and the remote circuit will draw a current of about 9mA. This current will cause a voltage drop of about 0.9V across R5 and the window comparator will detect this voltage and will change its state, switching off D3 and illuminating D2. When the water will reach the second rod, also pin #1 of IC1 will go high for the same reason explained above. Now either R3 and R4 will be connected across the full supply voltage and the total current drawing of the remote circuit will be about 18mA.
    The voltage drop across R5 will be now about 1.8V and the window comparator will switch off D2 and will drive D1. The battery will last very long because the circuit will be mostly in the off state. Current is needed only for a few seconds when P1 is pushed to check the water-level and one of the LEDs illuminates.

    Parts:

    • R1 = 15K 1/4W Resistors
    • R2 = 15K 1/4W Resistors
    • R3 = 1K 1/4W Resistors
    • R4 = 1K 1/4W Resistors
    • R5 = 100R 1/4W Resistor
    • R6 = 47K 1/4W Resistor
    • R7 = 3.3K 1/4W Resistors
    • R8 = 3.3K 1/4W Resistors
    • R9 = 2.7K 1/4W Resistors
    • R10 = 15K 1/4W Resistors
    • R12 = 15K 1/4W Resistors
    • R13 = 3.3K 1/4W Resistors
    • R14 = 2.7K 1/4W Resistors
    • R15 = 2.7K 1/4W Resistors
    • D1 = 3mm Green LED
    • D2 = 3mm Yellow LED
    • D3 = 3mm Red LED
    • C1 = 470nF 63V Polyester or Ceramic Capacitor
    • J1 = Two ways output sockets
    • J2 = Two ways output sockets
    • P1 = SPST pushbutton
    • B1 = 9V PP3 Battery
    • Q1 = BC547 45V 100mA NPN Transistor
    • IC1 = 4012 Dual 4 input NAND gate IC
    • IC2 = LM393 Dual Comparator IC
    • Two steel rods of appropriate length

    Notes:

    • The two steel rods must be supported by a small insulated (wooden) board
    • IC1 and R1-R4 are mounted on a small board placed near or on the steel rods support
    • The two-wire cable connecting the remote circuit board to the main control board, i.e. J1 to J2, can be of any size and type (preferably thin for obvious reasons). It can be very long, if necessary.
    • The circuit can be used also with non-metal tanks, provided a third steel rod having the height of the tank will be added and connected to pin #7 of IC1, R3, R4 and J1.
    • The 4012 chip was chosen because it contains two gates and was at hand, but you can use two of the gates contained into 4001, 4011, 4093, 4049, 4069 etc. chips, provided all inputs of each gate are tied together and all inputs of unused gates are connected to the positive rail, leaving output pins open.







    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Water-Level-Indicator-Circuit-Schematic_6164.html

    Stereo balance indicator circuit design electronic project

    This stereo balance indicator circuit diagram is designed using few common external components .The schematic circuit is very simple to build and will provide an visual indication with LEDs for left , right and center balance . Outputs from each channel are fed to the two inputs of IC1 connected as a differential amplifier . Output of the IC1 is connected to the noninverting inputs of the IC2 and IC3 . If the outputs of the IC1 approaches the supply rail , the outputs of the IC2 and IC3 will go high illuminating the LED 3 , this will show that the right channel is dominating . If the sound is balanced to the left channel , the Ic2 and IC3 will go low and the LED1 will light . If both channels are equal in amplitude the outputs of the IC2 and IC3 would be low and high respectively , lighting up LED2 .
    Circuit Diagram:
    Stereo balance indicator circuit design electronic project

    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/Stereo-balance-indicator-circuit-design-electronic-project_6157.html

    ULN2004 water level indicator circuit

    This ULN2004 electronic project circuit diagram design is a very simple water level indicator circuit project . This ULN2004 water level indicator circuit is very simple and require few external electronic parts .
    ULN2004 is a high voltage, high current darlington arrays that contain seven open collector darlington pairs with common emitters . Each channel rated at 500mA and can withstand peak currents of 600mA.
    As the water level rise in the tank , it comes in contact with probes P1 through P7 and thereby makes pins 7 trough 1 high sequentially . The corresponding output pins 10 trough 16 go low one after other and LED1 through LED7 will light up . When water comes in contact with the last probe P7 , the buzzer connected to the last pin 16 will sound .
    This electronic circuit project must be powered from a fixed output DC voltage that will provide an output voltage between 9 and 12 volts .



    ULN2004 water level indicator circuit design electronic project

    Source: http://www.hqew.net/circuit-diagram/ULN2004-water-level-indicator-circuit_6156.html

    Thursday, August 23, 2012

    Solve Elec

    Solve Elec software is a free piece of software that helps you to study circuits in direct current and alternating current .
    Solve Elec software is not a really circuit simulator software , but is very nice and good for students , which want to learn the basics of electronics .
    Why is not a really circuit simulator software ? because you can not simulate directly circuits , without to type any equation . If you want to study some electronic circuit diagrams using Solve elec , you’ll need to know some basics equations ( depends of complexity of circuit ) .
    Using this software you can :
    draw and analyze electrical circuits functioning in direct or alternating current
    -get literal formulas and values for current intensities and voltages defined in the circuit.
    -verify circuit related equations.
    -draw graphs.
    -get the equivalent circuit of displayed circuit
    -browse an integrated documentation
    -edit, save and print reports made of various elements displayed in main window
    To draw an electronic circuit using Solve Elec is very simple , you need just to click on the component you want to place and put it to the working area .
    You cannot use the designed circuit with other simulation (spice ) or pcb software .
    However this software is free and can be downloaded from physicsbox.com website .
    Also in the package delivered of this software you will find a very good help file that can help you to use the entire power of this software .
    This software can be very good for those who have time to type all required equations ( for all wanted parts from an circuit ) .
    This software is ok but it can be improved by the author , because you can not delete components or wires ( you must use cut shortcuts from keyboards ) , to simplify circuit analysis ( less equations ) , support for exporting or importing circuits from or to some other software .

    source: http://www.hqew.net/circuit-diagram/Solve-Elec_6137.html

    How to build Live Line Detector-Indicator Circuit Schematic

    Description

    If the unit is brought close to a live conductor (insulated, and even buried in plaster) capacitive coupling between the live conductor and the probe clocks the counter, and causes the LED to flash 5 times per second, because the 4017 IC divides the mains 50Hz frequency by 10. When remote from a live line, the unit stops counting, the LED resulting permanently off.

    Circuit diagram:

    Live Line Detector-Indicator Circuit Schematic-Circuit diagram

    Parts:

    • P1 = SPST Pushbutton
    • D1 = Red LED (any type)
    • C1 = 100nF 63V Polyester or Ceramic Capacitor
    • B1 = 3V Battery (two 1.5V AA or AAA cells in series etc.)
    • IC1 = 4017 Decade counter with 10 decoded outputs IC
    • Sensing probe 3 to 15 cm. long, stiff insulated piece of wire

    Notes:

    • Sensitivity can be varied using a more or less long sensing probe.
    • Due to 3V operation, the LED's current limiting resistor can be omitted.


    The article comes from http://www.hqew.net/circuit-diagram/How-to-build-Live-Line-Detector$2dIndicator-Circuit-Schematic_6130.htmlhttp://www.hqew.net/circuit-diagram/How-to-build-Live-Line-Detector$2dIndicator-Circuit-Schematic_6130.html

    ZenitPCB CAD software

    Zenit PCBis another useful software that can help you to design printed circuit boards . Zenit PCB is designed by Stortini Mirko Bruno and is completely freeware for personal or semi-professional use, limited to 800 pins . Zenit PCB is a flexible easy to use CAD program, which allow you to realize your projects in a short time . Zenit PCB has three main parts : Zenit PCB , Zenit Capture and Zenit Parts .
    If you will start a project in Zenit PCB you will see that the circuit diagram is very easy to draw , but maybe you will not found all needed components .
    If you try Zenit PCB you will see that the software is almost perfect , some useful features like :auto place component and auto router are missing .
    To see how Zenit PCB works we prepared a small video tutorial .
    Main steps to design a circuit using this software are very simple and require a few documentation , but on the package you will find a very good help file that show you all needed steps to design a printed circuit board from zero . Also on the developer website you can find some video tutorials that helps you to design a circuit .
    The software can be downloaded for free from this link or from the zenitpcb.com website .
    The most important steps that needs to be followed when you design a printed circuit board in Zenit PCB are :
    1. Place components in Zenit Capture
    2. Route all components
    3. Package parts
    4. Create Nets list
    5. Open Zenit PCB
    6. Place Board Outline
    7. Import Nets list
    8. Route the circuit
    The first thing that must be done before you place components and create Board outline for the PCB is to set the options for the circuit respective for the board .
    What I don’t like at this Printed Circuit Boards software ? If you will place for example three resistors R1 , R2 and R3 and you delete R2 from the circuit , the software doesn’t have any option for Auto annotation . This is not a big problem for a small project , because you have an option to rename components , but you’ll need to do that with all components one by one .
    Another interesting feature that is missing is zoom , I didn’t find shortcuts for zoom in and zoom out ( in Zenit Capture ) . In Zenit PCB you can use Page UP and Page Down for Zoom in and out or mouse scroll. Also I didn’t find a list for keyboard shortcuts , which is very useful when you design a circuit , because if you are using keyboard shortcuts , the design time can be reduced very much .
    Because of some missing options and some existing bugs , is a little difficult to design a circuit with this software without using a mouse . Zenit PCB window also has some important missing features , but maybe in the future this software will be improved by his designer . With all missing features this software is more better than some other paid circuit design software .
    Source: http://www.hqew.net/circuit-diagram/ZenitPCB-CAD-software_6144.html

    How to build Automatic Water Tank Filler Circuit Diagram

    Description

    This circuit has been very useful in filling a header tank for a reticulated water supply on a farm. Eight troughs are supplied in different paddocks where a lack of water would have serious consequences for the stock. In the past, the tank had been filled daily by a time clock which was not successful. During hot weather, the stock would empty the tank on a regular basis and then be without water for several hours or the tank would overflow and flood the area if the weather was wet and the cattle did not drink much.

    Circuit Diagram:

    Automatic Water Tank Filler Circuit Diagram-Circuit Diagram
    The circuit described has been used to maintain the level of water in the header tank within prescribed limits. It controls a 3HP submersible bore pump which has a high starting current, necessitating a solid-state relay sufficient to take the starting load. Two Darlington transistors, Q1 & Q3, in conjunction with Q2 & Q4, are connected to the upper and lower water sensors in the tank. Q2 & Q4 have a common 5.6kO load resistor and function as a NOR gate. The output of the NOR gate drives Q5 which activates relay RLY1.
    Initially, when the water level is low, both sensors will be open-circuit, the NOR gate output will be high and the relay will be turned on. This causes the normally closed (NC) contacts of the relay to open and disconnect the lower sensor. However, the upper sensor will still be open circuit and the NOR gate output will be high, keeping the relay closed. The normally open (NO) contact of the relay will be closed to operate the solid-state relay RLY2 to run the pump.
    This state continues until the water reaches the top sensor which will then drop the output from the NOR gate to 0V. The disables relay RLY1 and the pump is stopped. In practice the upper level sensor is just below the overflow from the tank and the lower sensor about half way up the tank. The sensor contacts are simply two stainless steel screws about 25mm apart and screwed through the poly tank walls. The wiring junctions on the side of the tank are protected by neutral-cure silicone sealant.




    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Automatic-Water-Tank-Filler-Circuit-Diagram_6122.html

    How to build Automatic Water Tank Filler Circuit Diagram

    Description

    This circuit has been very useful in filling a header tank for a reticulated water supply on a farm. Eight troughs are supplied in different paddocks where a lack of water would have serious consequences for the stock. In the past, the tank had been filled daily by a time clock which was not successful. During hot weather, the stock would empty the tank on a regular basis and then be without water for several hours or the tank would overflow and flood the area if the weather was wet and the cattle did not drink much.

    Circuit Diagram:

    Automatic Water Tank Filler Circuit Diagram-Circuit Diagram
    The circuit described has been used to maintain the level of water in the header tank within prescribed limits. It controls a 3HP submersible bore pump which has a high starting current, necessitating a solid-state relay sufficient to take the starting load. Two Darlington transistors, Q1 & Q3, in conjunction with Q2 & Q4, are connected to the upper and lower water sensors in the tank. Q2 & Q4 have a common 5.6kO load resistor and function as a NOR gate. The output of the NOR gate drives Q5 which activates relay RLY1.
    Initially, when the water level is low, both sensors will be open-circuit, the NOR gate output will be high and the relay will be turned on. This causes the normally closed (NC) contacts of the relay to open and disconnect the lower sensor. However, the upper sensor will still be open circuit and the NOR gate output will be high, keeping the relay closed. The normally open (NO) contact of the relay will be closed to operate the solid-state relay RLY2 to run the pump.
    This state continues until the water reaches the top sensor which will then drop the output from the NOR gate to 0V. The disables relay RLY1 and the pump is stopped. In practice the upper level sensor is just below the overflow from the tank and the lower sensor about half way up the tank. The sensor contacts are simply two stainless steel screws about 25mm apart and screwed through the poly tank walls. The wiring junctions on the side of the tank are protected by neutral-cure silicone sealant.




    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Automatic-Water-Tank-Filler-Circuit-Diagram_6122.html

    Wednesday, August 22, 2012

    How to build IR Music Transmitter and Reciever

    Description

    Using this circuit, audio musical notes can be generated and heard up to a distance of 10 metres. The circuit can be divided into two parts: IR music transmitter and receiver. The IR music transmitter works off a 9V battery, while the IR music receiver works off regulated 9V to 12V. First diagram shows the circuit of the IR music transmitter. It uses popular melody generator IC UM66 (IC1) that can continuously generate musical tones.

    Transmitter circuit diagram:

    Transmitter circuit diagram:
    The output of IC1 is fed to the IR driver stage (built across the transistors T1 and T2) to get the maximum range. Here the red LED (LED1) flickers according to the musical tones generated by UM66 IC, indicating modulation. IR LED2 and LED3 are infrared transmitting LEDs. For maximum sound transmission these should be oriented towards IR photo-transistor L14F1 (T3). The IR music receiver uses popular op-amp IC μA741 and audio-frequency amplifier IC LM386 along with photo-transistor L14F1 and some discrete components (second diagram).

    Receiver circuit diagram:

    Receiver circuit diagram:
    The melody generated by IC UM66 is transmitted through IR LEDs, received by phototransistor ceived by phototransistor T3 and fed to pin 2 of IC μA741 (IC2). Its gain can be varied using potmeter VR1. The output of IC μA741 is fed to IC LM386 (IC3) via capacitor C5 and potmeter VR2. The melody produced is heard through the receiver’s loudspeaker. Potmeter VR2 is used to control the volume of loudspeaker LS1 (8-ohm, 1W). Switching off the power supply stops melody generation.


    Source: http://www.hqew.net/circuit-diagram/How-to-build-IR-Music-Transmitter-and-Reciever_6114.html

    How to build Simple Short-Wave Transmitter

    Description

    This low-cost short-wave transmitter is tunable from 10 to 15 MHz with the help of ?J gang condenser VC1, which determines the carrier frequency of the transmitter in conjunction with inductor L1. The frequency trimming can be done with VC2. The carrier is amplified by transistor T4 and coupled to RF amplifier transistor T1 (BD677) through transformer X1*. The transmitter does not use any modulator transformer.
    The audio output from condenser MIC is preamplified by transistor T3 (BC548). The audio output from T3 is further amplified by transistor T2 (BD139), which modulates the RF amplifier built around transistor T1 by varying the current through it in accordance with the audio signal’s amplitude. RFC1 is used to block the carrier RF signal from transistor T2 and the power supply. The modulated RF is coupled to the antenna via capacitor C9.

    Circuit diagram:

    Simple Short-Wave Transmitter-Circuit diagram
    For antenna, one can use a 0.5m long telescopic aerial. Details of RF choke, inductor L1 and coupling RFC1 is used to block the carrier RF signal from transistor T2 and the power supply. The modulated RF is coupled to the antenna via capacitor C9. For antenna, one can use a 0.5m long telescopic aerial. Details of RF choke, inductor L1 and coupling transformer X1, we used a ready made short-wave antenna coil with tuning slug (Jawahar make), which worked satisfactorily. We tested the transmitter reception up to 75 metres and found good signal strength.






    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Simple-Short$2dWave-Transmitter_6103.html

    How to build Battery Powered Night Lamp

    Description

    This circuit is usable as a Night Lamp when a wall mains socket is not available to plug-in an ever running small neon lamp device. In order to ensure minimum battery consumption, one 1.5V cell is used and simple voltage doublers drives a pulsating ultra-bright LED: current drawing is less than 500μA. An optional Photo resistor will switch-off the circuit in daylight or when room lamps illuminate, allowing further current economy. This device will run for about 3 months continuously on an ordinary AA sized cell or for around 6 months on an alkaline type cell but, adding the Photo resistor circuitry, running time will be doubled or, very likely, triplicates. IC1 generates a square wave at about 4 Hz frequencies. C2 & D2 form voltage doublers, necessary to raise the battery voltage to a peak value able to drive the LED.

    Circuit Diagram:

    Battery Powered Night Lamp-Circuit Diagram

    Parts:

    • R1 = 1M
    • R2 = 1M
    • R3 = 47K
    • R4 = LDR
    • C1 = 100nF-63V
    • C2 = 220uF-25V
    • D1 = Ultra Bright 10mm LED
    • D2 = 1N5819
    • B1 = 1.5V Battery or AA Cell
    • IC1 = 7555 CMos Timer IC

    Notes:

    • IC1 must be a CMos type: only these devices can safely operate at 1.5V supply or less.
    • If you do not need Photo resistor operation, omit R3 & R4 and connect pin 4 of IC1 to positive supply.
    • Ordinary LEDs can be used, but light intensity will be poor.
    • An ordinary 1N4148 type diode can be used instead of the 1N5819 Schottky-barrier type diode, but LED intensity will be reduced due to the higher voltage drop.
    • Any Schottky-barrier type diode can be used in place of the 1N5819, e.g. the BAT46, rated @ 100V 150mA.


    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Battery-Powered-Night-Lamp_6102.html

    How to build Clap Sensitive On-Off Relay

    Description

    This circuit was intended to activate a relay by means of a hand clap. Further claps will turn-off the relay. An interesting and unusual feature of this project is the 3V battery operation. The circuit's sensitivity was deliberately reduced, in order to avoid unpredictable operation. Therefore, a loud hand clap will be required to allow unfailing on-off switching. Q1 acts as an audio amplifier. IC1 timer, wired as a monostable, provides a clean output signal and a reasonable time delay in order to allow proper switching of the following bistable circuit. A discrete-components circuit formed by Q2, Q3 and related parts was used for this purpose, in order to drive the Relay directly and to allow 3V supply operation.

    Circuit Diagram:

    Circuit Diagram

    Parts:

    • R1 = 12K
    • R2 = 1M
    • R3 = 6.8K
    • R4 = 220K
    • R5 = 2.2M
    • R7 = 100K
    • R8 = 22K
    • R9 = 6.8K
    • R10 = 100K
    • Q1 = BC550C
    • Q2 = BC328
    • Q3 = BC328
    • C1 = 220nF-63V
    • C2 = 22nF-63V
    • C3 = 220nF-63V
    • C4 = 22nF-63V
    • C5 = 22nF-63V
    • C6 = 47uF-25V
    • D1 = 1N4148
    • D2 = 1N4148
    • B1 = 3V Battery
    • IC1 = 7555 CMos IC
    • RL1 = DIL Reed-Relay SPDT
    • SW1 = SPST Switch
    • MIC1 = Electret Mic

    Notes:

    A small DIL 5V reed-relay was used in spite of the 3V supply. Several devices of this type were tested and it was found that all of them were able to switch-on with a coil voltage value comprised in the 1.9 - 2.1V range. Coil resistance values varied from 140 to 250 Ohm. Stand-by current consumption of the circuit is less than 1mA. When the Relay is energized, current drain rises to about 20mA.


    Source: http://www.hqew.net/circuit-diagram/How-to-build-Clap-Sensitive-On$2dOff-Relay_6107.html

    Tuesday, August 21, 2012

    How to build Portable Microphone Preamplifier Circuit Schematic

    Description

    This circuit is mainly intended to provide common home stereo amplifiers with a microphone input. The battery supply is a good compromise: in this manner the input circuit is free from mains low frequency hum pick-up and connection to the amplifier is more simple, due to the absence of mains cable and power supply. Using a stereo microphone the circuit must be doubled. In this case, two separate level controls are better than a dual-ganged stereo potentiometer. Low current drawing (about 2mA) ensures a long battery life.

    Circuit diagram:

    Circuit diagram

    Parts:

    • P1 = 2.2K
    • R1 = 100K
    • R2 = 100K
    • R3 = 100K
    • R4 = 8.2K
    • R5 = 68R
    • R6 = 6.8K
    • R7 = 1K
    • R8 = 1K
    • R9 = 150R
    • C1 = 1uF-63V
    • C2 = 100uF-25V
    • C3 = 100uF-25V
    • C4 = 100uF-25V
    • C5 = 22uF-25V
    • Q1 = BC560
    • Q2 = BC550

    Circuit Operation:

    The circuit is based on a low noise, high gain two stage PNP and NPN transistor amplifier, using DC negative feedback through R6 to stabilize the working conditions quite precisely. Output level is attenuated by P1 but, at the same time, the stage gain is lowered due to the increased value of R5. This unusual connection of P1, helps in obtaining a high headroom input, allowing to cope with a wide range of input sources (0.2 to 200mV RMS for 1V RMS output).

    Notes:

    • Harmonic distortion is about 0.1% @ 1V RMS output (all frequencies).
    • Maximum input voltage (level control cursor set at maximum) = 25mV RMS
    • Maximum input voltage (level control cursor set at center position) = 200mV RMS
    • Enclosing the circuit in a metal case is highly recommended.
    • Simply connect the output of this device to the Aux input of your amplifier through screened cable and suitable connectors.


    Reprinted Url Of This Article:
    http://www.hqew.net/circuit-diagram/How-to-build-Portable-Microphone-Preamplifier-Circuit-Schematic_6086.html

    How to build Moduler Preamplifier Circuit Diagram

    High Quality, Discrete Components Design, Input and Tone Control Modules

    To complement the 60 Watt MosFet Audio Amplifier a High Quality Preamplifier design was necessary. A discrete components topology, using and - 24V supply rails was chosen, keeping the transistor count to the minimum, but still allowing low noise, very low distortion and high input overload margin. Obviously, the modules forming this preamplifier can be used in different combinations and drive different power amplifiers, provided the following stages present a reasonably high input impedance (i.e. higher than 10KOhm).

    Main Module:

    If a Tone Control facility is not needed, the Preamplifier will be formed by the Main Module only. Its input will be connected to some sort of changeover switch, in order to allow several audio reproduction devices to be connected, e.g. CD player, Tuner, Tape Recorder, iPod, MiniDisc etc. The total amount and type of inputs is left to the choice of the home constructor. The output of the Main Module will be connected to a 22K Log. potentiometer (dual gang if a stereo preamp was planned). The central and ground leads of this potentiometer must be connected to the power amplifier input.

    Circuit diagram:

    Circuit diagram

    Parts:

    • R1_______________1K5 1/4W Resistor
    • R2_____________220K 1/4W Resistor
    • R3______________18K 1/4W Resistor
    • R4_____________330R 1/4W Resistor
    • R5______________39K 1/4W Resistor
    • R6______________56R 1/4W Resistor
    • R7,R10__________10K 1/4W Resistors
    • R8______________33K 1/4W Resistor
    • R9_____________150R 1/4W Resistor
    • R11_____________ 6K8 1/4W Resistor
    • R12,R13________100R 1/4W Resistors
    • R14____________100K 1/4W Resistor
    • C1_____________220nF 63V Polyester Capacitor
    • C2_____________220pF 63V Polystyrene or ceramic Capacitor
    • C3_______________1nF 63V Polyester or ceramic Capacitor
    • C4,C7___________47μF 50V Electrolytic Capacitors
    • C5,C6__________100μF 50V Electrolytic Capacitors
    • Q1,Q2_________BC550C 45V 100mA Low noise High gain NPN Transistors
    • Q3____________BC556 65V 100mA PNP Transistor
    • Q4____________BC546 65V 100mA NPN Transistor

    Tone Control Module:

    This Module employs an unusual topology, still maintaining the basic op-amp circuitry of the Main Module with a few changes in resistor values. A special feature of this circuit is the use of six ways switches instead of the more common potentiometers: in this way, precise "tone flat" setting, or preset dB steps in bass and treble boost or cut can be obtained. Tone Control switches also allow a more precise channel matching when a stereo configuration is used, avoiding the frequent poor alignment accuracy presented by common ganged potentiometers.
    Six ways (two poles for stereo) rotary switches were chosen for this purpose as easily available. This dictated the unusual "asymmetrical" configuration of three positions for boost, one for flat and two for cut. This choice was based on the fact that tone controls are used in practice more for frequency boosting than for cutting purposes. In any case, 5dB 10dB and 15dB of bass boost and -3dB and -10dB of bass cut were provided. Treble boost was also set to 5dB 10dB and 15dB and treble cut to -3.5dB and -9dB.
    Those wishing to use common potentiometers in the usual way for Tone Controls may use the circuit shown enclosed in the dashed box (bottom-right of the Tone Control Module circuit diagram) to replace switched controls. The Tone Control Module should usually be placed after the Main Input Module, and the volume control inserted between the Tone Control Module output and the power amplifier input. Alternatively, the volume control can also be placed between Main Input Module and Tone Control Module, at will. Furthermore, the position of these two modules can be also interchanged.

    Circuit diagram:

    Circuit diagram

    Parts:

    • R1,R7___________47K 1/4W Resistors
    • R2_____________220K 1/4W Resistor
    • R3______________18K 1/4W Resistor
    • R4_____________330R 1/4W Resistor
    • R5______________39K 1/4W Resistor
    • R6______________56R 1/4W Resistor
    • R8_____________150R 1/4W Resistor
    • R9______________10K 1/4W Resistor
    • R10,R16__________6K8 1/4W Resistors
    • R11,R12________100R 1/4W Resistors
    • R13____________100K 1/4W Resistor
    • R14______________1K5 1/4W Resistor
    • R15,R21,R22______4K7 1/4W Resistors
    • R17,R24,R26______8K2 1/4W Resistors
    • R18______________3K3 1/4W Resistor
    • R19______________1K 1/4W Resistor
    • R20____________470R 1/4W Resistor
    • R23,R25_________12K 1/4W Resistors
    • R27,R28__________4K7 1/4W Resistors
    • C1_____________220nF 63V Polyester Capacitor
    • C2_______________1nF 63V Polyester or ceramic Capacitor
    • C3,C6___________47μF 50V Electrolytic Capacitors
    • C4,C5__________100μF 50V Electrolytic Capacitors
    • C7______________10nF 63V Polyester Capacitor
    • C8,C9__________100nF 63V Polyester Capacitors
    • Q1,Q2_________BC550C 45V 100mA Low noise High gain NPN Transistors
    • Q3____________BC556 65V 100mA PNP Transistor
    • Q4____________BC546 65V 100mA NPN Transistor
    • SW1,SW2_______2 poles 6 ways Rotary Switches
    • Simpler, alternative Tone Control parts:
    • P1______________22K Linear Potentiometer
    • P2______________47K Linear Potentiometer
    • R29,R30________470R 1/4W Resistors
    • R31,R32__________4K7 1/4W Resistors
    • C10_____________10nF 63V Polyester Capacitor
    • C11,C12________100nF 63V Polyester Capacitors

    Power supply:

    The preamplifier must be feed by a dual-rail, 24 and -24V 50mA dc power supply. This is easily achieved by using a 48V 3VA center-tapped mains transformer, a 100V 1A bridge rectifier and a couple of 2200μF 50V smoothing capacitors. To these components two 24V IC regulators must be added: a 7824 (or 78L24) for the positive rail and a 7924 (or 79L24) for the negative one. The diagram of such a power supply is the same of that used in the Headphone Amplifier, but the voltages of the secondary winding of the transformer, smoothing capacitors and IC regulators must be uprated. Alternatively, the dc voltage can be directly derived from the dc supply rails of the power amplifier, provided that both 24V regulators are added.

    Note:

    If this preamplifier is used as a separate, stand-alone device, thus requiring a cable connection to the power amplifier, some kind of output short-circuit protection is needed, due to possible shorts caused by incorrect plugging. The simplest solution is to wire a 3K3 1/4W resistor in series to the output capacitor of the last module (i.e. the module having its output connected to the preamp main output socket).

    Technical data:

    • Main Module Input sensitivity:
    • 250mV RMS for 1V RMS output
    • Tone Control Module Input sensitivity:
    • 1V RMS for 1V RMS output
    • Maximum output voltage:
    • 13.4V RMS into 100K load, 11.3V RMS into 22K load, 8.8V RMS into 10K load
    • Frequency response:
    • flat from 20Hz to 20KHz
    • Total harmonic distortion @ 1KHz:
    • 1V RMS 0.002% 5V RMS 0.003% 7V RMS 0.003%
    • Total harmonic distortion @10KHz:
    • 1V RMS 0.003% 5V RMS 0.008% 7V RMS 0.01%







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    How to build Thunderstorm Predictor

    Description

    Sure, listening to VHF FM has great advantages over MW/LW AM from the old days — now we have bright stereo free from interference, fading and noise! However, your FM radio will no longer predict the arrival of a thunderstorm as did the AM radio many years ago-reliably and hours before the trouble was upon you! The crux is that AM detection will faithfully reproduce the effects of lightning and other massive static discharges approaching in a very simple way: they’re audible as slight crackling noises in the loudspeaker, almost irrespective of the tuning of the radio! Assuming no AM radio is available anymore, a dedicated VLF receiver tuned to about 300 kHz can faithfully detect the crackle of approaching lightning.
    The simple receiver shown here consists of a loosely tuned amplifier driving a kind of flasher circuit that blinks an LED in synchronicity with the lightning bolts. The frequency and intensity of the LED activity indicates the intensity and distance of the storm respectively. Looking at the circuit diagram, the LED driver is not biased to flash until a burst of RF energy, amplified by T1, arrives at the base of T2. The receiver works off 3 volts and has a negligible standby current of about 350 microamperes which will hardly dent the shelf life of a couple of 1.5-V D-size cells. T2 and T3 form a monostable generator triggered by sudden drops in T1’s collector voltage.

    Circuit diagram:

    Circuit diagram:
    Preset P1 is adjusted until the LED remains off when you’re sure there’s no thunderstorm around for a few hundred miles. The value of the LED series resistor is subject to experimentation and LED current. L2, C1 and the antenna are coarsely tuned for resonance at about 300 kHz. Frequency-wise, lightning is a fairly broadband phenomenon so any tuning to between 200 and 400 kHz will be fine for the circuit but make sure you’re not accidentally tuned to a nearby VLF transmitter! The input signal is obtained from a 70-cm long piece of stiff wire, with coil L1 inserted for impedance matching and lengthening the antenna electrically.

    Warning:

    This circuit and in particular the antenna must not be used to attract lightning. Consequently, neither the circuit nor the antenna may be used outdoors and/or powered from the mains.
    Source: http://www.hqew.net/circuit-diagram/How-to-build-Thunderstorm-Predictor_6092.html

    Monday, August 20, 2012

    How to build A Regularly Repeating Interval Timer

    Description

    This circuit has an adjustable output timer that will re-trigger at regular intervals. The output period can be anything from a fraction of a second to half-an-hour or more - and it can be made to recur at regular intervals of anything from seconds to days and beyond.

    Schematic Diagram

    Schematic Diagram

    The Output Section

    The output section is a simple Monostable Circuit . When Pin 6 of the Cmos 4001 is taken high - the monostable triggers - and the relay energizes. It will remain energized for a period of time set by C1 & R3.
    With the values shown - R3 will provide output periods of up to about 30-minutes. However, you can choose component values to suit your requirements. For example, if you reduce R3 to 1meg - and C1 to 4.7uF - the maximum output period is between 3 and 5 seconds. Owing to manufacturing tolerances - the precise length of the time period available depend on the characteristics of the actual components you've used.

    The Cmos 4060

    The Cmos 4060 is a 14-bit binary counter with a built-in oscillator. The oscillator consists of the two inverters connected to Pins 9, 10 & 11 - and its frequency is controlled by R7. The output from the oscillator is connected internally to the binary counter. While the oscillator is running - the IC counts the number of oscillations - and the state of the count is reflected in the output pins.
    By adjusting R7 - you can set the length of time it takes for any given output pin to go high. Connect that output to Pin 6 of the Cmos 4001 and - every time it goes high - it'll trigger the monostable.
    Ideally C4 should be non-polarized - but a regular electrolytic will work - provided it doesn't leak too badly in the reverse direction. Alternatively - you can simulate a non-polarized 10uF capacitor by connecting two 22uF capacitors back to back - as shown.

    IMPORTANT

    Do not use the "on-board" relay to switch mains voltage. The board's layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe - Away From The Board. I've used a SPCO/SPDT relay - but you can use a multi-pole relay if you wish.

    Veroboard Layout

    Veroboard Layout
    Since the delays between outputs can last for hours - or even days - using "Trial and Error" to set-up the timer would be very tedious. A better solution is to use the Setup Table provided - and calculate the time required for Pin 7 of the Cmos 4060 to go high.
    For example, if you want the monostable to trigger every Six Hours - the Range Table tells you to use Pin 1 of the Cmos 4060. You need Pin 1 to go high every 6 x 60 x 60 = 21 600 seconds. The Setup table tells you that for Pin 1 you should divide this figure by 512 - giving about 42 seconds. Adjust R7 so that the Yellow LED lights 42 seconds after power is applied. This will cause Pin 1 to go high after about 3 Hours.

    The Setup Tables

    The Setup Tables
    When Pin 1 goes high it will stay high for three hours. It will then go low for three hours - before going high once again. Thus, Pin 1 goes high once every six hours. It's the act of going high that triggers the monostable. So - after an initial delay of three hours - the relay will energize. It will then re-energize every six hours thereafter.
    The reset button should NOT be used during setup. The time it takes for Pin 7 to go high - and the Yellow LED to light - MUST be measured from the moment power is applied.
    Although R4, R5 and the two LEDs help with the setup - they are not necessary to the operation of the timer. If you want to reduce the power consumption - disconnect them once you've completed the setup. If you want the LEDs to glow brighter - use brighter LEDs. Don't be tempted to reduce the values of the series resistors - especially R5. If you reduce its value too far - the oscillator output will not operate the counter.
    The timer is designed for a 12-volt supply. However - provided a suitable relay is used - it will work at anything from 5 to 15-volts. Applying power starts the timer. It can be reset at any time by a brief interruption of the power supply - so a reset button is not strictly necessary. If you need delays in excess of 32-hours - increase the value of C4.
    The Support Material for this circuit includes a step-by-step guide to the construction of the circuit-board - a parts list - a detailed circuit description - and more.
    Source: http://www.hqew.net/circuit-diagram/How-to-build-A-Regularly-Repeating-Interval-Timer_6061.html

    How to build 555 timer Mono stable (one shot) circuit

    Description

    The two circuits below illustrate using the 555 timer to close a relay for a predetermined amount of time by pressing a momentary N/O push button. The circuit on the left can be used for long time periods where the push button can be pressed and released before the end of the timing period. For shorter periods, a capacitor can be used to isolate the switch so that only the initial switch closure is seen by the timer input and the switch can remain closed for an unlimited period without effecting the output.

    In the idle state, the output at pin 3 will be at ground and the relay deactivated. The trigger input (pin 2) is held high by the 100K resistor and both capacitors are discharged. When the button is closed, the 0.1uF cap will charge through the button and the 100K resistor which causes the voltage at pin 2 to move low for a few milliseconds. The falling voltage at pin 2 triggers the 555 and starts the timing cycle. The output at pin 3 immediately moves up to near the supply voltage (about 10.4 volts for a 12 volt supply) and remains at that level until the 22 uF timing capacitor charges to about 2/3 of the supply voltage (about 1 second as shown). Most 12 volt relays will operate at 10.4 volts, if not, the supply voltage could be raised to 13.5 or so to compensate. The 555 output will supply up to 200mA of current, so the relay could be replaced with a small lamp, doorbell, or other load that requires less than 200mA. When the button is released, the 0.1uF capacitor discharges through the 100K and 2K resistors. The diode across the 100K resistor prevents the voltage at pin 2 from rising above the supply voltage when the cap discharges. The 2K resistor in series with the 22uF cap limits the discharge current from pin 7 of the timer. This resistor may not be necessary, but it's a good idea to limit current when discharging capacitors across switch contacts or transistors.

    Circuit diagram

    Circuit diagram




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    How to build Repeating Timer No3

    Description

    This circuit is very similar to Repeating Timer No.2. However - the addition of the light dependent resistor means that the operation of this timer can be limited to the daylight hours. R7 lets you set the level of light at which the timer will stop. The type of LDR is not critical. The important thing is the voltage on pin 1. Any type of LDR should work satisfactorily. But you may need to change the value of R7 - to achieve the desired range of adjustment.

    Schematic Diagram

    Schematic Diagram

    Setting The Timer

    The circuit is basically an Astable Oscillator. And the output times depend on the value of C1 - and the speed at which it charges and discharges through the resistor network. The length of time the relay remains energized is controlled by R1 & R2. And the length of the time it remains de-energized is controlled by R3 & R4. The fixed resistors set the minimum period lengths - and the maximum period lengths are set by R2 & R3. With the component values shown - both periods are adjustable from about 1 to 30 minutes.
    You can change the component values to suit your own requirements. If your time periods don't need to be too precise - and more-or-less is close enough - you can leave out the pots altogether - and simply rely on R1 & R4 to set the times. Owing to manufacturing tolerances - the precise length of the time periods available depends on the characteristics of the actual components you've used - and a 4093 will produce longer time periods than a 4011.

    IMPORTANT

    Do not use the "on-board" relay to switch mains voltage. The board's layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe - Away From The Board. I've used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application.

    Alternative Capacitor

    When the oscillator is running - the polarity of the charge on C1 keeps reversing. So C1 needs to be non-polarised. However - you can simulate a non-polarised 470uF capacitor by connecting two 1000uF polarised capacitors back to back - as shown. How and why this works is explained in the Detailed Circuit Description. Because non-polarised capacitors aren't widely available - the prototype was built using two polarised capacitors.

    Veroboard Layout

    Veroboard Layout
    The timer is designed for a 12-volt power supply. However - it will work at anything from 5 to 15-volts. All you need do is select a relay with a coil voltage that suits your supply.

    Part list

    Part list




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