LED Voltage Level Indicator

This circuit is derived from a Siemens Application Note 1974. This circuit uses common components of today.

The circuit is here as it is of high educational value. I have not tested it. You can ‘simulate and test’ or ‘wire it up and try’ and let me know how it worked. The Circuit is also a simple analog to digital converter. You can use optos in place of LEDs.

T1 and T2 make a differential amplifier. T3, T4 and T5 driving the LEDs are comparators. Now to learn more on how they work you have to study circuits at 4QD-TEC and search Educypedia for more. Some pspice ideas here and at 101Science.com.

When input voltage is increased T1 is turned on which leads to more base current for T3 which Lights LED1. When input voltage is less T2 turns on as it gets a better base current from P3 which turns on LED2 via T4. When both LEDs are off T5 gets biased as no drop across R5 which lights the LED3 thru T5 hopefully.
What you need to know is a small current Ib thru the base-emitter path in the direction of the emitter arrow will lead to a large Current Ic thru the emitter-collector path in direction of arrow. Ic = B * Ib where B – beta is the DC current gain, it could be 100-400 see Towers International Transistor Selector see chipdir.

Beta is different in each transistor you buy and varies with the test conditions and even with temperature and age. The LED1 and LED2 will indicate above or below Limits set by P2 and P1. The Limit Threshold itself is set at P3 i think. LED3 will light when Hi LED and Lo LED both are off.

The applications of this circuit are FM tuning indicator, Stereo Balance Indicator (Wire T2 like T1 then we get two channel inputs) and battery level indicator.

Passive volume control with Potentiometer

Volume control circuit for speaker 4 ohm or 8 ohm located in the another room far away. by using only passive components.


a simple circuit you can build at home at low cost it uses just a rotary switch and wire wound resistors. Add more resistors and a rotary switch with more contacts for finer control.

Reprinted Url Of This Article: http://www.hqew.net/circuit-diagram/Passive-volume-control-with-Potentiometer_12414.html

Mains Voltage Indicator with a LED

This is a mains 230V AC voltage indicator and is a LIVE CIRCUIT, so take care. The Resistor has to be a fusible ceramic wire wound and the capacitor 630V AC or higher capacity.

This circuit has been drawn from my memory and i have not tried it out again, just see if it is ok and then try. You should use the fuse of 100mA a slow blow if you want but it is very important. This circuit has to be enclosed in a plastic sealed enclosure to avoid contact.

Reprinted Url Of This Article: http://www.hqew.net/circuit-diagram/Mains-Voltage-Indicator-with-a-LED_12416.html

TV Muter Circuit

Many households are still graced by tube-type television sets. If you want to connect one of these large tellies to your stereo system to improve the sound quality, this is usually not a problem because there are plenty of SCART to Cinch adapters available in accessory shops. However, with some sets your pleasure is spoiled by the fact that the audio outputs of the SCART connector are not muted during channel switching.

This can sometimes lead to nasty signal spikes, which can cause the loudspeakers of your stereo system to emit irritating popping and cracking noises. In such cases it is a good idea to fit your system with a mute circuit. Fortunately, the right time to activate the mute circuit is defined by the fact that the happy zapper presses buttons on the remote control to switch channels, and the remote control emits IR signals.

There are even inexpensive ready-made IR receiver modules available, such as the TSOP1136 used here, which produce trains of active-low pulses in response to such signals. About the circuit: when no IR signal is present, a capacitor is charged via P2 and a diode. IC1 is a comparator that compares this IR voltage (applied to its non-inverting input on pin 3) to a voltage applied to its other input on pin 2.

Circuit diagram:

TV Muter Circuit Diagram

This reference voltage, which can be adjusted with P1, determines the switching threshold of the comparator. If IC2 receives an IR signal, T2 conducts, and as a result the voltage on C1 drops rapidly below the threshold level set by P1. This causes T1 to change from its previous ‘on’ state to the ‘off’ state. As a result, the relay drops out and the audio link to the stereo system is interrupted for the duration of the noise interval.

It’s all quite simple, as you can see. If you do not have a stabilized 5-V supply voltage available, you can use the circuit at the of the schematic diagram (with a 5-V voltage regulator) together with a simple (unstabilised) AC mains adapter that supplies a voltage in the range of 9 V to 12 V to the 7805 (IC3). You can also use a relay with normally-closed contacts instead of normally-open contacts.

In this case, simply swap the signals on pins 2 and 3 of IC1 so the relay pulls in when an IR signal is received instead of dropping out. This saves a bit of power because the relay is only energized during zapping. If you can’t find any worthwhile use for the second comparator of IC1, it’s a good idea to connect pin 6 to 5 V and pin 5 to ground. To improve noise immunity, you should shield the IR sensor so it is not exposed directly to light from a fluorescent fixture. http://www.hqew.net/circuit-diagram/TV-Muter-Circuit_12634.html

Earth Fault Indicator

The security of many electrical devices depends today on the availability of an earthed mains outlet. We should remember that these are connected to the frame or to the metal housing of the equipment and so it routes to the protective earth (PE) connections. In this setup, mains voltage, however small, will cause the differential circuit breaker to trip. The circuit breaker is part of any modern electrical installation. This type of security device may however become defective due to common corrosion as we have seen many times on various older household devices, as well as on construction sites.

Actually, since these devices are frequently in wet conditions, the screw and/or lug used to connect the earth wire to the device frame corrodes gradually and ends up breaking or causing a faulty contact. The remedy is then worse than the problem because the user, thinking that he/she is protected by earth, does not take special precautions and risks his/her life. However, all that’s needed is an extremely simple system to automatically detect any break in the earth connection; so simple that we ask ourselves why it is not already included as part of all factory production for appliances that carry any such risk, as we have discussed above.

We propose it as a project for you to build using this schematic. The live wire (L) of the mains power supply is connected to diode D1 which ensures simple half-wave rectification which is sufficient for our use. The current which is available is limited to a very low value by resistor R2. If the appliance earth connection to which our circuit is installed is efficient, this current is directed to earth via resistor R1 and the rest of the circuit is inactive due to insufficient power. If the earth connection is disconnected, the current supplied by D1 and R2 charges up capacitor C1.

Circuit diagram:

Earth Fault Indicator Circuit Diagram

When the voltage at the terminals of the capacitor reaches about 60 volts, neon indicator light La1 is turned on and emits a flashing light which discharges capacitor C1 at the same time. This phenomenon is reproduced indefinitely as long as the earth connection has not been restored, and the neon light continues to flash to attract attention in case of danger. Building the project is not particularly difficult but, since it is a project aimed at human safety, we must take the maximum of precautions concerning the choice of components utilised. Therefore, C1 must have an operating voltage of at least 160 volts while R2 must be a 0.5-watt resistor, not for reasons of power dissipation, but in order to maintain the voltage.

The neon light can be any type, possibly used, or it may be part of an indicator light to make it easier to attach to the protected appliance. In the second case, we must obviously get rid of its series resistor which would prevent proper operation here. During installation of the circuit in the appliance to be protected, we should also clearly mark Live (L) and Neutral (N) (for example, seek Live with a simple screwdriver) because inverting these two wires at this point will disable proper operation. The final point, which is self-evident considering the principle used here: the earth connection for our setup must be hooked up to the frame of the appliance to be protected at a different point than where the normal earth wire is connected.http://www.hqew.net/circuit-diagram/Earth-Fault-Indicator_12621.html

Digital Main Voltage Indicator

Continuous monitoring of the mains voltage is required in many applications such as manual voltage stabilisers and motor pumps. An analogue voltmeter, though cheap, has many disadvantages as it has moving parts and is sensitive to vibrations. The solidstate voltmeter circuit described here indicates the mains voltage with a resolution that is comparable to that of a general-purpose analogue voltmeter. The status of the mains voltage is available in the form of an LED bar graph. Presets VR1 through VR16 are used to set the DC voltages corresponding to the 16 voltage levels over the 50-250V range as marked on LED1 through LED16, respectively, in the figure. The LED bar graph is multiplexed from the bottom to the top with the help of ICs CD4067B (16-channel multiplexer) and CD4029B (counter).

The counter clocked by NE555 timer-based astable multivibrator generates 4-bit binary address for multiplexer-demultiplexer pair of CD4067B and CD4514B. The voltage from the wipers of presets are multiplexed by CD4067B and the output from pin 1 of CD4067B is fed to the non-inverting input of comparator A2 (half of op-amp LM358) after being buffered by A1 (the other half of IC2). The unregulated voltage sensed from rectifier output is fed to the inverting input of comparator A2. The output of comparator A2 is low until the sensed voltage is greater than the reference input applied at the non-inverting pins of comparator A2 via buffer A1.

When the sensed voltage goes below the reference voltage, the output of comparator A2 goes high. The high output from comparator A2 inhibits the decoder (CD4514) that is used to decode the output of IC4029 and drive the LEDs. This ensures that the LEDs of the bar graph are ‘on’ up to the sensed voltage-level proportional to the mains voltage.The initial adjustment of each of the presets can be done by feeding a known AC voltage through an auto-transformer and then adjusting the corresponding preset to ensure that only those LEDs that are up to the applied voltage glow.
20N60 Circuit         ICL7107CPL Circuit               SSM2164 Circuit

Note.
It is advisable to use additional transformer, rectifier, filter, and regulator arrangements for obtaining a regulated supply for the functioning of the circuit so that performance of the circuit is not affected even when the mains voltage falls as low as 50V or goes as high as 280V. During Lab testing regulated 12-volt supply for circuit operation was used.)

Water Level Alert

Beeper or flashing LED alert, 1.5V battery powered portable unit

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This circuit will emit an intermittent beep (or will flash a LED) when the water contained into a recipient has reached the desired level. It should be mounted on top of the recipient (e.g. a plastic tank) by means of two crocodile clips, acting also as probes. If a deeper sensing level is needed, the clips can be extended by means of two pieces of stiff wire (see pictures).

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Circuit operation:

IC1, a 555 CMos timer chip, is wired as an astable multivibrator whose operating frequency is set by C1, R1 and R2, plus the resistance presented by water across the probes. If the resistance across the probes is zero (i.e. probes shorted), the output frequency will be about 3Hz and the sounder will beep (or the LED will flash) about three times per second. As water usually presents a certain amount of resistance, the actual oscillation frequency will be lower: less than one beep/flash per second. As probes will be increasingly immersed in water, the resistance across them will decrease and the oscillation frequency of IC1 will increase.

This means that a rough aural or visual indication of the level reached by water will be available. If a LED is chosen as the alert, C2, D1 and D2 must be added to the circuit in order to double the output voltage, thus allowing proper LED operation (see the rightmost part of the schematics). Interesting features of this circuit are 1.5V supply and ultra-low current consumption: 40μA in stand-by and 0.5mA in operation. This allows a single AAA alkaline cell to last several years and the saving of the power on/off switch.

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Pictures of the project:

Screenshoot - Water Level Alert Circuit Schematic

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Circuit diagram:

Water Level Alert Circuit Diagram

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Parts:

R1 = 1K - 1/4W Resistor
R2 = 100K - 1/4W Resistor (See Notes)
C1 = 2.2uF-50V Electrolytic Capacitor
C2 = 220μF - 25V Electrolytic Capacitor (See Notes)
D1 = 5 or 10mm. Ultra-bright red LED (See Notes)
D2 = 1N5819 - 40V 1A Schottky-barrier Diode (See Notes)
IC = 7555 or TS555CN CMos Timer IC
BZ = Piezo sounder (incorporating 3KHz oscillator)
B1 = 1.5V Battery (AAA or AA cell etc.)
Two small crocodile clips
Two pieces of stiff wire of suitable length
Battery socket, etc.

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Notes:

• If a LED alert is needed instead of the beeper, R2 value must be changed to 10K, the Piezo sounder can be omitted and D1, D2 and C2 must be added, as shown in the rightmost part of the schematics.
• A common red LED can be used for D1, but ultra-bright types are preferred.
• Any Schottky-barrier type diode can be used in place of the 1N5819, e.g. the BAT46, rated @ 100V 150mA.
• Wipe the probes regularly to avoid excessive resistance variations due to partial oxidization.

Source: http://www.hqew.net/circuit-diagram/Water-Level-Alert_12617.html

30 watt audio amplifier based TDA2040

A 30 watt audio amplifier circuit using TDA2040 are shown here. TDA2040 is class AB monolithic integrated audio amplifier available in the package Pentawatt. The IC has a low harmonic distortion and has a built in circuit protection for short circuit.
In the circuit, two TDA2040 ICs are wired in BTL (bridge-tied load) configuration to provide 30W of output into 8 ohm speakers at /-16V DC. The capacitor C1 is the decoupling capacitor DC input. Network with components R2, C4, R3 provides feedback for IC1 while R7, C6, R8 network provides information for IC2. Network C5, R5 and C9, R9 provides stability at high frequency. Capacitors C2, C3 filters the positive supply rail while the capacitors C7, C8 filters the negative supply rail.
30 watt audio amplifier Parts list :
R1, R2, R4, R6, R7 : 22k
R3, R8 : 680 ohm
R5, R9 : 4.7 ohm
C1 : 2.2uF
C2, C7 : 100uF
C3, C8 : 100nF
C4, C6 : 22uF
C5, C9 : 0.1uF
IC1, IC2 : TDA2040

Reprinted Url Of This Article: http://www.hqew.net/circuit-diagram/30-watt-audio-amplifier-based-TDA2040_12047.html

15 w class B audio amplifier

Below is a circuit diagram of class B 15 Watts audio amplifier is designed using a dual op-amp and transistor.
The 15 W class B audio amplifier circuit shown here is a simple class B audio amplifier based on?LM833 op amp, TIP41 and TIP42 transistors. LM833 is a dual operational amplifier with high scanning speed and low distortion designed specifically for audio applications. This audio amplifier circuit can provide 15 watts of audio output to a 8-12 ohm speaker with a supply voltage of /-12V DC dual power.
Dual operational amplifier in the LM833 IC is used here. IC1a is wired as a buffer and C3 works as input decoupling capacitor DC. IC1b is wired inverter mode and it provides a negative feedback. Complementary power transistors TIP41 and TIP42 are wired in Class B push pull system and they drive the speaker. Diode D1 provides a bias voltage of 0.7 V in pair of push-pull and capacitors C2 protect 0.7 V bias voltage through D1 from heavy surge voltage at the output of IC1b.
Notes:
The audio amplifier circuit should be mounted on good quality PCB.
Use a support for mounting IC1.
Use a 12 /-12V dual power supply to supply the amplifier.
Potentiometer R2 can be used as a volume control.
Increase the supply voltage will increase power output.
Anyway notefollowing points.
TIP42 and 41 can only handle up to 6A.
IC1 maximum supply voltage can handle is 16/16 V DC.

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30W Stereo power amplifier based TDA 1521

It is small?and?compact?stereo?amplifier?is?powerful?but?can easily be used?to?replace?your?broken?amplifier or?new construction,?or?to?make?an active?speaker,?in all cases?combined with a preamplifier. With?remarkable features?make?it?the true?Hi-Fi?amplifier.
Using?only?active?component?(the right and?left channel)?Philips?TDA1521?monolithic integrated?circuit,?which?contains a?double?line-end?audio?amplifier completely independent,?each capable of?providing?from?10 to?12 W?to?the load?8 ohm?or?15 W?into 4?ohms?(30?W?music). Voltage?gains?of the?amplifier?is?fixed?at 30?dB.
SPECIFICATIONS:
-?Power supply:?12?V?symmetrical?dual?voltage
-?Maximum Power Output?RMS:?2 x 15W?/ 4?ohms, 2?x?10 W?/ 8?ohms
-?Maximum power output?music:?2?x?30 W?/ 4?ohms
-?Harmonic Distortion:?0.007%?(1 W?/ 1?kHz)
-?Input sensitivity:?300 mV?/ 20?kOhms
- Frequency:?7 Hz?to 60?kHz?(-3?dB)
-?70 dB?for each channel
-?Output power (R?= 8?ohms):?2?x?10 W?RMS
-?Output power (R?=?4 ohms):?2?x?15 W?RMS
-?Bandwidth?(-3?dB): 7 to?60 000?Hz
- Sensitivity?to maximum power?(8?ohms):?290?mVrms
- Sensitivity?to maximum power?(4?ohms):?250?mVrms
-?Input impedance:?20?kilohms
-?S / N Ratio:?98 dB
-?Crosstalk: -70?dB
- High quality stereo amplifier
- Low?noise
- Protection?against overload
Parts?list :
R1?….?8.2?Ω?1/4?W
R2?….?8.2?Ω?1/4?W
C1?….?22 nF?ceramic
C2?….?22 nF?ceramic
C3?….?100?nF?multilayer
C4?….?1 uF?63?V?Polyester
C5?….?1 uF?63?V?Polyester
C6?….?4700?uF?25?V?electrolytic
C7?….?4700?uF?25?Vélectrolytique
D1?….?1N5404
D2?….?1N5404
D3?….?1N5404
D4?….?1N5404
U1?….?TDA1521
Miscellaneous :
1 ……?heatsink?(Rth?less than 3.3?° C / W)
2 ……?3MA?bolts?12 mm?Unless otherwise specified,?all
resistors are?1/4?W?5%

Source:http://www.hqew.net/circuit-diagram/30W-Stereo-power-amplifier-based-TDA-1521_12051.html

10 W amplifier using TDA2003

This is a circuit diagram of amplifier circuit, these circuits have a 10W audio power amplifier using TDA2003 IC from SGS Thomson popular. The IC can easily provide 10W into 4 Ohms load at 18V DC supply voltage. IC can also be operated from 12V and that makes it applicable in a car audio system. Useful features include TDA2003 short circuit protection between all pins, thermal overload protection, low harmonic distortion, low distortion. The circuit given here is designed according to the datasheet from the manufacturer and found to be working well. The following is a schematic drawing:

L6562 Circuit      TL494CN Circuit           TDA7388 Circuit

C7 capacitor DC input work decoupling.R2 and R3 are used to adjust the gain of R1 determines amplifier.C3 and cut off the top frequency.C6 and R4, and is intended to increase the stability of high frequency. The capacitor C5 couples the output to the speakers. You can try this circuit diagram for your car audio power amplifier or to a small room.

Audio Perimeter Monitor System

Circuit diagram with the names we call the perimeter audio monitor, which is intended for audio surveillance of areas not protected, for example into the back garden or open space. Circuit diagram using a single cable such as speaker doorbell wire or cable, this circuit can be far positioned, for example, at the bottom of the garden or garage, and is used to detect all sound in that area. Cable can be buried in a water pipe or channel and hidden from view. The mic is a regular dynamic mic insert and should be placed in a cage with a water resistant entire series. The output mic reinforced by two transistors, the output is fed into the cable through a 220u capacitor. Here, he has a dual purpose disrupt supply to prevent DC bias of the circuit, and also allows the audio output of smaller ac to pass to the front. In the power supply, audio found by the 10k preset and 220u capacitor. This is used to feed a small audio amplifier (such as design 2watt) previously displayed on this site. The following is a schematic drawing:

PT2272 Circuit            LM2904 Circuit              L7812CV Circuit

Mini Simple Buzzer Electronic

?This is a mini buzzer circuit electronic, circuit NE555 is used as a sound generator. When the switch is in the closed position, electric current is passed to the circuit. Installation of resistors and capacitors are useful for controlling the time period buzzer sounds in the IC NE555. pulse signal when the IC is positive, then the buzzer sounded. here I also include a PCB (printed circuit board) of the mini buzzer electronic and you can also download it. Here is a schematic drawing Simple Mini Electronic Buzzer:

Mini Simple Buzzer Electronic

PCB Mini Simple Buzzer Electronic

Motor Speed Control Circuit USing LM3524

The LM3524,   LM2904 in an arrangement which controls the speed of a motor without requiring the usual tachometer or other speed pick-off. The output transistors, paralleled in the common emitter configuration, drive the 2N5023 and the motor turns. The LM3524 output pulse is also used to drive a 1000 pF-500 kW differentiator network whose output is compared to the LM3524 internal 5V reference. The 10k-4k divider at the motor output insures the LF398 output will always be within the common range of the LM3524’s input. The 10k 1 μF combination provides filtering during the time the LF398 is sampling. Here is a schematic drawing:

The diode associated with this time constant prevents any possible LF398 negative output from damaging the LM3524. The 10 MOhm resistor paralleling the 0.01 μF sampling capacitor prevents the servo from “hanging up” if this capacitor somehow manages to charge above the motor’s back EMF value. The 39k 100 μF pair sets the loop frequency response. The maximum pulse width modulator (PWM) duty cycle is clamped by the 2k-2k divider and diode at 80%, thus avoiding overshoot and aiding transient response at turn-on and during large positive step changes. The 60k-0.1 μF values at pins 6 and 7 set the pulse modulation frequency at 300 Hz.

75W Transistor Audio Amplifier

It is simple to build an amplifier, using the standard and stable and reliable. The 75 W amplifier circuit presented here is capable of driving 4 ohm, but, although used in 4 ohms, this amplifier has very few errors.
To be aware that there are no short-circuit output, so that when the speaker short, while the amplifier is working (with signal), there is a very real danger that may damage the transistor.
Characteristic of the 75W Transistor Audio Amplifier are as follows …
Sensitivityto 74 Watts output power – a little less than 1W (1W is 75W)
Gain– 27 dB
Frequency range(-3dB) – 10Hz to 23kHz @ 1W
THD, 1 kHz – 0.05% (typical maximum)
Open loop gain– 125dB (no load), 80dB (8 Ohm load)
Input Impedance– 22k ohms
DC-Offset– less than 100 mV (<20 mV typical **)
Noise– <2 mV at the output (-80dB unweighted ref 50W)

Source: http://www.hqew.net/circuit-diagram/75W-Transistor-Audio-Amplifier_12080.html

10 W Audio Amplifier based TDA 2003

With only one active integrated circuit TDA 2003 as component this circuit can provide up to 10W of audio power to the load which can be between 2 and 8 ohm.
As usual integrated circuit TDA2003, should be placed with which appropriate heat sink to prevent damage to internal components on the temperature of the IC.
10 W audio amplifier circuit requires a current to voltage V max 18VDC 2A to work correctly.
The low power audio amplifier is obtained at the optimal point of the work load of 4 Ω. These entries must be at least 1Vpp to achieve this performance.
10 W Audio Amplifier parts list :
R1 : 100 k?potentiometer
R2 : 47?Ω
R3 : 220?Ω
R4 : 2.2?Ω
R5 : 1?Ω
C1 : 2.2?uF
C2 : 470?uF
C4 : 100 nF
C5 : 1000?uF
C6 : 100 nF
C3 : 47 nF
IC1 : TDA2003
4?Ω?speaker?SPK

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100 W valve audio amplifier

This is a valve audio amplifier circuit which can provide power up to 100W, here there are only schematics and component list for the explanation you can find on the internet.
Valve audio amplifier parts list :

R1 10 kΩ	C1 0.22 μF	Q1?7199 P
R2 100 kΩ	C2 0.2 μF	Q2?6L6GC
R3 220 kΩ	C3 0.5 μF	Q3?6L6GC
R4 820 kΩ	C4 0.5 μF	Q4 7199T
R5 15 kΩ	C5 0.2 μF	Q5 6SN7
R6 47 kΩ		Q6 6SN7
R7 100 kΩ
R8 3.9 kΩ
R9 8 Ω
R10 820 Ω
R11 22 Ω
R12 390 Ω
R13 15 kΩ
R14 1 MΩ
R15 1 kΩ
R16 3.8 kΩ
R17 1 kΩ
R18 3.8 kΩ
R19 1 MΩ
R20 75 kΩ
R21 47 kΩ
R22 100 kΩ
R23 3.9 kΩ
R24 75 kΩ
R25 10 Ω

24C08     TLP250          CA3140         AT90CAN128

PLL Module   This schematic originally comes from a Dutch magazine called Free Radio Magazine in the mid eighties. It's just a PLL nothing more, nothing less. The resistor named R can be replaced by a 50 Ohm type if the power supply is 5 Volts. The dividing ratio can be programed with IC2. For the ratios see table 1. Example: If the input signal has a frequency of 10MHz, the crystal frequency output is 10.240-10.000=0.24. Now looking at table 1, we see we can make 24 by combining the 8 and 16 program switches (pin 11 and pin 12 closed to Vcc). By trimming coil T the output will lock to 10MHz. To use this PLL in the 3 meter band (100MHz), divide the oscillator frequency by 10. Next feed this signal to pin 4 from IC1 by a 8pF capacitor. The adjust voltage coming from IC2 pin 5 should be connected to the oscillator's varicap by a 4k7 resistor. As described here, the PLL will make frequency stepping of 10kHz, to change it to 5kHz apply around minus 9V to pin 4 from IC2. When using this PLL in the 3 meter band, this will result in stepping of 50kHz instead of 100kHz.

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http://www.hqew.net/circuit-diagram/PLL-Module_12082.html

2x4W Stereo Tube Amplifier Circuit

Here the schematic diagram of 2x4W stereo tube amplifier which built based 5 power tubes component. This amplifier will produces up to 4 watt audio power for each output channel.
Components list:
C1, C4 = 200pF/600v
C2, C5 = 47nF/600v
C3, C6 = 22uF/25v
C7 = 47uF/450V
C8 = 33nF/450V
C9 = 10nF/1400v

R1A & B = 500KΩ Dual gang Potentiometer
R2, R6 = 1MΩ 1/2W
R3, R7 = 470KΩ 1/2W
R4, R8 = 220KΩ 1/2W
R5, R9 = 330Ω, wire-wound or metal oxide 2W
R10 = 750Ω, wire-wound 20W
Audio Output Transformer T2, T3
Primary (impedance) = 3300 ? @ 400 cycles
Secondary (impedance) = 4 or 8 ? @ 400 cycles
Power Transformer, T1
Primary = 117v 60 cycles
Sec. 1 = 600v CT @ 80mA
Sec. 2 = 5v @ 2A
Sec. 3 = 6.3v @ 4A
Tubes:
6SQ7-GT
6V6-GT
5Y3-GT – Full-wave vacuum rectifier
Circuit notes:

• For finest audio reproduction results, 90db/watt speakers or higher efficiency should be utilized.
• Do not forget hook-up wire, sockets, switch, and also a chassis or circuit board. All tubes are octal type and will require an octal socket.
• Shield any hook-up wires utilized within the signal path between the input jack and the first audio tube.
• R10 will create considerable heat, and care needs to be taken in its location. I utilized a large adjustable wire wound resistor for this and mounted it above the chassis. A choke coil in its place would give better performance and more closely resemble the electromagnet field inside the prototype.
• A choke coil with a DC resistance approximate to 750 ohms may possibly be substituted for R10.

Source: http://www.hqew.net/circuit-diagram/2x4W-Stereo-Tube-Amplifier-Circuit_11977.html

315 Watt Class D Power Amplifier

This audio amplifier based? TAS5261 (bridge digital amplifier) has output power of 315 watts per channel and an efficiency up to 96% is suitable for use in a variety of Sound applications, such as home theater systems.
Reducing the cost and availability of high-bit ADC and digital signal processors have contributed to the emergence of high power amplifiers, D-class, based on pulse-width modulation. Work output transistor stages in a key mode of such amplifiers allows a few, sometimes dozens of times to increase efficiency, thereby reducing heat generation amplifier, its size and cost. Among all the audio amplifier device class D are the most cost-effective, thanks to the use of digital signal processing. It eliminates the possibility of distortion and noise in the pre-amplifier paths, streamlines and simplifies all kinds of linear and nonlinear signal conversion without using mechanical adjustment components, extends the functionality.

Frequency response, Hz	10 … 40 000
Power Output	235 (RLoad = 4 ohms, THD <0.15%)? 315 (RLoad = 4 ohms, THD <10%)? 125 (RLoad = 8 ohms, THD <0.09%)? 220 (RLoad = 6 ohms, THD <10 %)
Load resistance, Ohm	4 … 16
The range of volume, dB	-100 … 17
Nominal input voltage, V	1
Sampling frequency input signal, kHz	96
S / N ratio, dB	-99
Total harmonic distortion noise, dB	-93
Current consumption in standby mode, not more than, mA	10
Nominal input voltage, V	1
Power supply circuit “ 50″ in	(50)
Power supply circuit “ 12″ stabilized,	12

2SK170 Circuit
24C08 Circuit

Audio Frequency Amplifier 20W based LM1875

This scheme requires a minimum number of components. The amplifier has a good performance and very low harmonic distortion. At the main component of the amplifier is chip LM1875 company National Semiconductor , which has protected against short circuit and overheating.
Specifications:
Voltage : 48 V DC
Current Consumption : 1 A
Output Power : 20 W at 4 ohms
Gain : 26 dB
Band : 20 Hz … 20 kHz

Reprinted Url Of This Article:
http://www.hqew.net/circuit-diagram/Audio-Frequency-Amplifier-20W-based-LM1875_11972.html

Courtesy Light Extender

In essence, this circuit is a 15 to 20-second courtesy light extender for cars. It is activated in the usual way by opening a door but it also samples the negative lock/unlock signals from a car alarm or central locking and does two more things. First, when an unlock signal is received, it turns on the courtesy light for 15-20 seconds before you open the door. Second, when a lock signal is received, it turns off the courtesy light immediately, with no fade-out. This is done to eliminate false triggering of the burglar alarm through current drain sensing. When a car door is open or the unlock relay is activated, the 33μF capacitor discharges through diode D1 and this keeps transistor Q1 turned off.

Circuit diagram:

Courtesy Light Extender Circuit Diagram

This allows Q2 and Q3 to turn on and the courtesy lamp is activated. When the door is closed, the courtesy lamps stay illuminated and the 33μF electrolytic capacitor starts charging through the associated 1MO resistor. As the voltages rises, Q1 turns on slowly, turning off Q2 and Q3 which gradually fades out the courtesy lamp. If a lock signal from the central locking system is received, relay 1 closes and charges the capacitor instantly, so the lamp turns off immediately. Relays were used to interface to the central locking/alarm system as a safety feature, to provide isolation in case something goes wrong.
Source: http://www.hqew.net/circuit-diagram/Courtesy-Light-Extender_12662.html

Automatic White-LED Garden Light

This white-LED driver circuit is ideal for use in a garden light. It automatically turns the LED on at night and runs from a single 1.2V nicad cell which is recharged by a solar cell during the day. The prototype used the existing casing and solar cell from an old garden light but you could also use a solar cell from a solar education kit. Diode D1 allows the solar cell to charge the battery during the day and prevents it from discharging back into the solar cell at night. Transistor Q1 controls the LED driver circuit. This transistor is normally on during the day (ie, when there is output from the solar cell) and so Q2 and the LED are off.

At night time, Q1 is off and this allows a simple blocking oscillator circuit based on T1, R2 and Q2 to operate. This circuit in turn drives LED1 via a 1W resistor which limits the peak current into the LED. T1 is wound bifilar, with the two windings configured to produce a center-tapped winding. Winding AB is the main primary winding and winding BC is the feedback winding. The number of turns and the core used are not critical. The prototype worked with a toroid scrounged from an old computer power supply, as well as with a small ferrite suppression bead and an Altronics L5110 core.

Circuit diagram:

Automatic White-LED Garden Light Circuit Diagram

The toroids were wound using 10 turns of 0.25mm wire, while the ferrite bead worked with just five turns of 0.25 mm wire through the hole (that's all that would fit). The oscillator works like this: when Q1 turns off, current flows through R2 and turns Q2 on. This causes current to flow through winding AB and the core produces a magnetic flux. And that in turn causes end C on the transformer to rise above the battery voltage and turn Q2 on hard. When the core saturates, the voltage at C drops back to the battery voltage, thus reducing the current in winding AB. As this happens, the flux in the core starts to fall and this causes the voltage at C to drop below 0.6V.

As a result, Q2 turns off and because there is now no current in AB, the flux in the core starts to collapse. What happens now is that the voltage on end A of the windings rises above the battery voltage. When it gets to 3.2-3.6V with respect to ground, LED1 "fires" and current flows from the battery via BA, through the LED and back to the battery. When the flux is spent, LED1 turns off and end C returns to the battery voltage. Current now flows through R2 and into the base of Q2 and the whole cycle starts over again. Finally, when the Sun rises the following morning, Q1 turns on, robs Q2 of its base drive, the oscillation stops and LED1 goes out.

Multicolor HD LED

Most PC enclosures provide only a single LED to indicate hard disk access, with the LED being connected to the motherboard via a two-pin connector. However, this LED only works with IDE drives, and if a SCSI disk controller is fitted, its activity will not be visibly noticeable. This small circuit remedies that problem using a multicolour LED. The activity LED for the IDE interface is usually driven by a connected device via one or more open-collector stages.

Picture of the project:

Multicolor HD LED Circuit

It illuminates if either of the two possible IDE drives is activated. The shared series resistor limits the current and also provides short-circuit protection. Even if the LED is shorted out due to faulty wiring, the current is restricted to a safe level. An obvious solution would be to have the IDE and SCSI disks drive a shared dual LED, but unfortunately the current flows from the positive supply line through a series resistor, the LED and a transistor to ground.

The dual LED would thus have to have a common anode, but no such device exists. All known multicolor LEDs have a common cathode lead. That means they cannot be connected directly, but we’re not that easily defeated. Only a small additional circuit is needed to allow the LED to be driven by the different interfaces. In this circuit, each of the drive signals from the two controllers is fed to an optocoupler, which acts nearly the same as the original LED.

Circuit diagram:

Multicolor HD LED Circuit Diagram

The somewhat lower voltage drop of the infrared LED results in a somewhat greater current, but there’s hardly any need to worry about overloading. The optocouplers eliminate the problems with the different voltages. On the output side, a Darlington transistor consisting of the photo-transistor and a BC547 drives the multicolour LED. The 10-k resistor (whose value of is not critical) provides secure cut-off of the driver transistor.

The base of the phototransistor in the CNY17 is left open. The series resistors for the individual LED elements are dimensioned using the standard formula. It may be necessary to adjust their values slightly, depending on the relative brightness levels. The circuit can also operated from the 12-V line of the power supply if the values of the series resistors for the LEDs are suitably modified.

Parts and PCB layout:

L7805CV   RFP450   2SK170  24C08 

Parts and PCB Layout Of Multicolor HD LED

If necessary, a third optocoupler stage can be added to allow a three-colour LED (red, green and blue) to be driven. The circuit board has been designed to be so small that the components can be fitted in a few minutes and everything can be suspended from the LED in the PC enclosure. A drop of hot-melt glue will prevent the circuit board from becoming dislodged due to vibration. The supply voltage reaches the circuit via a normal small drive connector, to make it easy to obtain the necessary plug. Otherwise, you can also use ordinary solder pins.

COMPONENTS LIST
Resistors:
R1,R3 = 10k
R2,R4 = 560R
Semiconductors:
D1 = Dual LED with 3 pins
IC1,IC2 = CNY17-2
T1,T2 = BC547B
Miscellaneous:
K1 = 4-way SIL connector
Small disk drive connector for PCB
mounting, or solder pins (see text)

Using LED As A Light Sensor

This circuit shows how to use an ordinary LED as a light sensor. It makes use of the photovoltaic voltage developed across the LED when it is exposed to light. LEDs are cheaper than photodiodes and come with a built-in filter, which is useful when the application involves colour discrimination. The photo-voltage of a red LED (its bandgap voltage) is typically about 2V. The source impedance of this voltage is about 800MΩ in daylight, rising to infinity in darkness. A TL071 JFET input op amp is used to amplify and buffer this extremely high impedance signal.

Circuit diagram:

LED As A Light Sensor Circuit Diagram

Resistor R1 ensures that the op amp "sees" a 0V input when the LED is in total darkness. To avoid undue loading of the signal, R1 would ideally be a 100MΩ or larger resistor but since such high values are rare and expensive I used a smaller value and increased the gain of the op amp to compensate for the voltage loss. To avoid the need for a second variable resistor to set the op amp’s input offset to zero, R1 must be large enough for the reduced voltage across the LED to swamp the op amp’s input offset voltage. With a 30MΩ resistor for R1, the voltage at the op amp input when the LED is exposed to bright light is reduced to about 60mV.

This is just over four times the 13mV maximum input offset of the TL071 op amp. R1 can be three 10MΩ resistors in series. Alternatively, I have found that a reverse-biased 1N4148 diode has an impedance of about 30MΩ (connect it in the circuit with the anode to ground). The output of the circuit is about 0V when the LED is in darkness. VR1 sets the gain of the op amp and it should be adjusted to give the required output voltage when the LED is exposed to bright light. http://www.hqew.net/circuit-diagram/Using-LED-As-A-Light-Sensor_12671.html

USB Printer Share Switch Circuit Project

mousReading(2)Collection this page

This simple device allows two computers to share a single USB printer or some other USB device, such as an external flash drive, memory card reader or scanner. A rotary switch selects the PC that you wish to use with the USB device, while two LEDs indicate the selected PC.

The most common way to share a USB printer between two PCs is to use one machine as a print server. However, that’s not always convenient because it means that the server PC must always be on if you want to print something.

Picture of the project:

That can be a real nuisance if you just want to quickly fire up the other machine and print something out. It also means that the two PCs must be networked together, either via a hub/router or directly via an ethernet crossover cable.

Another way is to use a dedicated USB print server. However, as before, this must be connected to an ethernet network, along with the PCs. Such devices also need their own power supply, generally cost well over $100 and are overkill if you just want to share a single USB printer between two computers for occasional printing in a home set-up.

Parts layout:

That’s where this simple device comes in. It’s basically a 2-way switch box that lets you manually switch your USB printer from one PC to the other, as required. The switching is performed using a rotary switch, while two LEDs on the front panel indicate which PC has been connected to the printer.

This method has several advantages. First, you don’t need to network your two computers. Second, you can print from either machine with the other turned off. And third, the device doesn’t need a power supply.

More circuits at http://www.hqew.net/circuit-diagram/USB-Printer-Share-Switch-Circuit-Project_12583.html

Baud Rate Generator

In this article, an RC oscillator is used as a baud rate generator. If you can calibrate the frequency of such a circuit sufficiently accurately (within a few percent) using a frequency meter, it will work very well. However, it may well drift a bit after some time, and then…. Consequently, here we present a small crystal-controlled oscillator. If you start with a crystal frequency of 2.45765 MHz and divide it by multiples of 2, you can very nicely obtain the well-known baud rates of 9600, 4800, 2400, 600, 300, 150 and 75. If you look closely at this series, you will see that 1200 baud is missing, since divider in the 4060 has no Q10 output!

If you do not need 1200 baud, this is not a problem. However, seeing that 1200 baud is used in practice more often than 600 baud, we have put a divide-by-two stage in the circuit after the 4060, in the form of a 74HC74 ?ip-?op. This yields a similar series of baud rates, in which 600 baud is missing. The trimmer is for the calibration purists; a 33 pF capacitor will usually provide sufficient accuracy. The current consumption of this circuit is very low (around 1mA), thanks to the use of CMOS components.

Source: http://www.hqew.net/circuit-diagram/Baud-Rate-Generator_12585.html

Pulse Rate Monitor

This simple circuit enables you to listen to your heartbeat, for instance, while you are exercising. The transducer used for detecting the pulse is an electret microphone, X1 in the diagram. The model used has two (polarized) terminals. As usual with this type of microphone, it functions via a series resistor, R1. The potential drop across this resistor is applied to op amp IC1a via C1. The amplification of the op amp is set to between ´40 and ´1000 with preset P1. Network R4-C3 in the feedback loop of IC1a is a low-pass filter with a cut-off frequency of 34 Hz. Higher frequencies are not needed for the present application. A pulse rate of 180* is equivalent to a frequency of 3 Hz.
MAX232 Circuit   PT100 Circuit  CR2032 Circuit 
So as to cater for a wide range of pulse rates, the cut-off frequency is made just over 11 times as high as that representing the highest pulse rate. Operational amplifier IC1c, in conjunction with push-pull am-plifier T1-T2, creates a headphone amplifier, whose output resistance is equivalent to the value of R9, that is, 47 ?. This makes the circuit usable for virtually any kind of headset. The output is short-circuit-proof. In case of certain headphones, such as that used with Sony Walkman™ sets, it is best to connect the two earphones in series. Operational amplifier IC1b is used as an active potential divider. The voltage across the actual divider, R5-R6, is half the supply voltage.

Pulse Rate Monitor Circuit Diagram

This voltage is buffered by IC1b, taken from the low-resistance output, pin 7, of this op amp and used as reference for IC1a, and as operating voltage for the electret microphone. The voltage is decoupled by C4 to remove any interference signals from it. The supply voltage for the pulse rate monitor is decoupled by capacitor C7, immediately after polarity protection diode D1. Owing to the use of CMOS op amps, the current drain does not exceed 10 mA, so that operation from a 9 V battery is perfectly feasible. A dry alkaline manganese battery will have a life of about 50 hours.

Unless you are a young superfit top-class athlete, you should see your GP immediately when you find you have a pulse rate of 180. As a general guide, the absolute maximum pulse rate for a young, very fit person is 180, for a middle-aged person, 160, and for an elderly person, 140. When exercising, the pulse rate of a not very fit person should not exceed 60% of these maxima.

Call Acknowledged

This circuit could be used (depending on your circumstances) by a gentleman to summon his butler, a manager his secretary or as in the author’s case to call the kids down to dinner without having to shout above the level of the CD player/TV/games console in their bedroom. Rather than resorting to a full-blown intercom system, a simpler solution was envisaged and while a buzzer could easily fulfil this function, this circuit has the advantage of providing a visual indication of a call as well as confirming to the caller that the ‘message’ has been received.

This is especially useful in the latter case, as the call may be easily drowned out by the music playing in the headphones. The circuit, which requires no complicated switching, uses a simple two-wire connection between the two stations and utilises the fact that the forward voltage drop of a blue (or white) LED is greater than that of a red, green or yellow one. The circuit is based on a two-transistor multivibrator which is used to pulse a red LED (D3) as well as the buzzer Bz1 on and off at about 1.5 Hz when push button S1 is closed. This frequency may of course be altered if required by changing the values of the capacitors.

Circuit diagram:

 

Call Acknowledged Circuit Diagram

The diode D1 in series with the collector of transistor T2 is required to isolate the output from the effects of the buzzer circuitry, which would alter the multivibrator frequency. In principle, the multivibrator could be dispensed with but a pulsed buzzer/flashing led is much more noticeable than a continuous signal especially in noisy conditions. Since the voltage across a red LED is typically about 1.5 V while a blue LED requires at least 2.5 V to 3 V to light, the blue LED will remain off when the call button S1 is pressed. Despite being rated for operation at 3-12 V, most piezo sounders can still produce a piercing sound from the pulsed 1.5-V available across the red LED which should get the attention of even the most preoccupied teenager.
74HC595 Circuit   DS1302 Circuit  TL494 Circuit  IRF3205 Circuit
When the recipient presses the acknowledge (push to break) switch S2, the red LED/buzzer are disconnected allowing the blue LED to flash at the sending station indicating to the caller that his call has been received. Alternatively, if a blue LED is not available, a red or green type in series with a forward biased silicon diode to raise its forward voltage above that of the red LED in the receiver could be used instead. The circuit may be powered by a 9-V battery, a mains power supply being unnecessary in view of the low power consumption and infrequency of use of the circuit.

30CPQ060PBF Datasheet

30CPQ060PBF FEATURES
• 150 °C TJ operation
• Very low forward voltage drop
• High frequency operation
• High purity, high temperature epoxy encapsulation for enhanced mechanical strength and moisture resistance
• Guard ring for enhanced ruggedness and long term reliability
• Compliant to RoHS Directive 2002/95/EC
• Designed and qualified according to JEDEC-JESD47
• Halogen-free according to IEC 61249-2-21 definition (-N3 only)
TL494 PDF   IRF3205 PDF  TDA2822 PDF  2N3055 PDF 
30CPQ060PBF DESCRIPTION
The VS-30CPQ… center tap Schottky rectifier has been optimized for very low forward voltage drop, with moderate leakage. The proprietary barrier technology allows for reliable operation up to 150 °C junction temperature. Typical applications are in switching power supplies, converters, freewheeling diodes, and reverse battery protection.
More details about 30CPQ060PBF Datasheet.

Source: http://partsparty.com/30cpq060pbf-datasheet/

What’s LM3914?

The LM3914 is a monolithic integrated circuit that senses analog voltage levels and drives 10 LEDs, providing a linear analog display. A single pin changes the display from a moving dot to a bar graph. Current drive to the LEDs is regulated and programmable, eliminating the need for resistors. This feature is one that allows operation of the whole system from less than 3V.
The circuit contains its own adjustable reference and accurate 10-step voltage divider. The low-bias-current input buffer accepts signals down to ground, or Vb, yet needs no protection against inputs of 35V above or below ground. The buffer drives 10 individual comparators referenced to the precision divider. Indication non-linearity can thus be held typically to (/2%, even over a wide temperature range. Versatility was designed into the LM3914 so that controller, visual alarm, and expanded scale functions are easily added on to the display system. The circuit can drive LEDs of many colors, or low-current incandescent lamps. Many LM3914s can be “chained” to form displays of 20 to over 100 segments. Both ends of the voltage divider are externally available so that 2 drivers can be made into a zero-center meter. The LM3914 is very easy to apply as an analog meter circuit. A 1.2V full-scale meter requires only 1 resistor and a single 3V to 15V supply in addition to the 10 display LEDs. If the 1 resistor is a pot, it becomes the LED brightness control. The simplified block diagram illustrates this extremely simple external circuitry.
L7805CV    4N35   93C46   IR2110   LM324N   4N25   LF353  
When in the dot mode, there is a small amount of overlap or “fade” (about 1 mV) between segments. This assures that at no time will all LEDs be “OFF”, and thus any ambiguous display is avoided. Various novel displays are possible.
Much of the display flexibility derives from the fact that all outputs are individual, DC regulated currents. Various effects can be achieved by modulating these currents. The individual outputs can drive a transistor as well as a LED at the same time, so controller functions including “staging” control can be performed. The LM3914 can also act as a programmer, or sequencer.
The LM3914 is rated for operation from 0§C to a70§C. The LM3914N is available in an 18-lead molded (N) package. The following typical application illustrates adjusting of the reference to a desired value, and proper grounding for accurate operation, and avoiding oscillations.

HCF4066M013TR Datasheet

• 15V DIGITALOR ± 7.5V PEAK TO PEAK SWITCHING
• 125W TYPICAL ON RESISTANCE FOR 15V OPERATION
• SWITCH ON RESISTANCE MATCHED TO WITHIN 5W TYP. OVER 15V SIGNAL INPUT RANGE
• ON RESISTANCE FLAT OVER FULL PEAK TO PEAK SIGNAL RANGE
• HIGH ON/OFF OUTPUT VOLTAGE RATIO : 65dB TYP. at fIS = 10KHz, RL = 10KW
• HIGH DEGREE OF LINEARITY : < 0.5% DISTORTION TYP. at fIS = 1KHz, VIS = 5 Vpp, VDD - VSS > 10V, RL = 10KW
• EXTREMELY LOW OFF SWITCH LEAKAGE RESULTING IN VERY LOW OFFSET CURRENT AND HIGH EFFECTIVE OFF RESISTANCE : 10pA TYP. at VDD – VSS = 10V, Tamb = 25°C
• EXTREMELY HIGH CONTROL INPUT IMPEDANCE (control circuit isolated from signal circuit 1012W typ.)
• LOW CROSSTALK BETWEEN SWITCHES : 50dB Typ. at fIS = 0.9MHz, RL = 1KW
• MATCHED CONTROL – INPUT TO SIGNAL OUTPUT CAPACITANCE : REDUCES OUTPUT SIGNAL TRANSIENTS
• FREQUENCY RESPONSE SWITCH ON :40MHz (Typ.)
• QUIESCENT CURRENT SPECIF. UP TO 20V
• 5V, 10V AND 15V PARAMETRIC RATINGS
• INPUT LEAKAGE CURRENT II = 100nA (MAX) AT VDD = 18V TA = 25°C
• 100% TESTEDFOR QUIESCENT CURRENT
• MEETS ALL REQUIREMENTS OF JEDEC JESD13B ” STANDARD SPECIFICATIONS FOR DESCRIPTION OF B SERIES CMOS DEVICES”

HCF4066M013TR DESCRIPTION
The HCF4066B is a monolithic integrated circuit fabricated in Metal Oxide Semiconductor technology available in DIP and SOP packages. The HCF4066B is a QUAD BILATERAL SWITCH intended for the transmission or multiplexing of analog or digital signals.
It is pin for pin compatible with HCF4016B, but exhibits a much lower ON resistance. In addition, the ON resistance is relatively constant over the full input signal range. The HCF4066B consists of four independent bilateral switches. A single control signal is required per switch. Both the p and n device in a given switch are biased ON or OFF simultaneously by the control signal. As shown in schematic diagram , the well of the n-channel device on each switch is either tied to the input when the switch is ON or to VSS when the switch is OFF. This configuration eliminates the variation of the switch-transistor threshold voltage with input signal, and thus keeps the ON resistance low over the full operating signal range. The advantages over single channel switches include peak input signal voltage swings equal to the full supply voltage, and more constant ON impedance over the input signal range. For sample and hold applications, however, the HCF4016B is recommended.
Source: http://partsparty.com/hcf4066m013tr-datasheet/



More parts datasheet:

BS170  PDF   2N7002 PDF        S8050 PDF     TIP122 PDF     L7805CV PDF

Flip-Flop Timer Using 4017

This circuit shows how a 4017 CMOS decade counter can be used to build a timer circuit. Push-button S1 will discharge capacitor C1 through resistor R2. When S1 is released, C1 will charge up through R1 causing a rising edge at the clock input of IC1. This causes the output Q1 to go high (to the supply voltage). Current will ?ow through R4 and LED D2 will light. At the same time C2 will begin charging through preset P1 and R6. When the voltage on C2 reaches approximately half the supply voltage it will reset IC1. Q1 will go low, the LED will go off and C2 will discharge through D1 and R3. The circuit will now remain stable in this reset condition until S1 is pressed again. Preset P1 allows the ON time of the circuit to be adjusted between 5 seconds and 7 minutes.
LM393    LM555          LM386     NE555
The current consumption of this circuit in its reset state is only a few micro-amps, rising to approximately 8mA mainly due to the LED current, when S1 is pressed. When power is applied to the circuit IC1, can be in an indeterminate state and the LED may be on. Pressing S1 until the LED goes off clears this condition. Alternatively C2 may be connected to the supply rail (as shown dotted in the diagram) this will ensure that IC1 will always power up in a reset state. A disadvantage of this con?guration is that any noise on the supply rail will be coupled through to the reset pin of IC1 and may affect the timing period. Source: http://www.hqew.net/circuit-diagram/Flip$2dFlop-Timer-Using-4017_12560.html

Audio Booster

Small and portable unit, Can be built on a veroboard

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S8050 PDF   TIP122 PDF          L7805CV PDF
The amplifier's gain is nominally 20 dB. Its frequency response is determined primarily by the value of just a few components-primarily C1 and R1. The values of the schematic diagram provide a response of ±3.0 dB from about 120 Hz to better than 20,000 Hz.Actually, the frequency response is ruler flat from about 170 Hz to well over 20,000 Hz; it's the low end that deviates from a flat frequency response. The low end's roll-off is primarily a function of capacitor C1(since RI's resistive value is fixed). If C1's value is changed to 0.1 pF, the low end's comer frequency-the frequency at which the low-end roll-off starts-is reduced to about 70 Hz. If you need an even deeper low-end roll-off, change C1 to a 1.0 pF capacitor; if it's an electrolytic type, make certain that it's installed into the circuit with the correct polarity, with the positive terminal connected to Q1's base terminal.

---

Circuit diagram:

Audio Booster Circuit Diagram

---

Parts:
P1 = 100K
R1 = 47K
R2 = 470K
R3 = 10K
R4 = 560R
R5 = 270R
C1 = 0.1uF-25v
C2 = 3.3uF-25v
C3 = 470uF-25V
D1 = 5mm. Red Led
B1 = 9v Battery
J1 = RCA Audio Input Socket
J2 = RCA Audio Output Socket
S1 = On-Off Switch

Source: http://www.hqew.net/circuit-diagram/Audio-Booster_12559.html

Pump it up: Mp3 Booster

MP3 players are all the rage these days. The smaller ones in memory-stick format are particularly easy to take with you; your very own ‘personal sound system’ on the move! It’s when you want others to share your taste in music that you ?nd these players to have a lack of power. You can get round this problem with the help of the MP3 booster, a small amplifier that can be used to connect your MP3 player directly to your Hi-Fi. When you next invite your friends to a party you can ask them to bring their ‘personal music’ as well as the usual drinks!

But ?rst we have to build this booster! The small battery-powered players have an output signal that is more than suf?cient to drive a set of 32 Ohm headphones. You’ll often ?nd that with an output of 1mW the sound pressure level (SPL) produced can reach up to 90 dB. This would be suf?cient to cause permanent damage to your hearing after only one hour! The maximum output voltage will then be around 200mV. This, however, is insuf?cient to fully drive a power amplifier. For this you’ll need an extra circuit that boosts the output voltage.

Power amps usually require 1 V for maximum output, hence the signal has to be ampli?ed by a factor of ?ve. We will also have to bear in mind that quieter recordings may need to be ampli?ed even more. We’ve used a simple method here to select the gain, which avoids the use of potentiometers. After all, the MP3 player already has its own volume control. We decided to have two gain settings on the booster, one of three times and the other ten times. Ampli?ers IC1A and IC1B (for the right and left channels) are housed in a single package, a TS922IN.

The output signal of the MP3 player is fed via a stereo cable and socket K1 to the inputs of the amplifiers. The gain depends on the relationship between resistors R2 and R1 (R6 and R5 for the other channel) and is equal to ten times. When you add jumper JP1 (JP2), resistor R3 (R7) will be connected in parallel with the negative feedback resistor R1 (R6), which causes the gain to be reduced to about three. When you start using the booster you can decide which gain setting works best for you.

Circuit diagram:

MP3 Booster Circuit Diagram

Resistor R4 (R8) takes the ampli?ed MP3 signal to the output socket K2 (K3). A cable then connects these phono sockets to the input of your power amplifier. The resistors connected in series with the output (R4 and R8) are there to keep the booster stable when a long cable is connected to its output. Cables have an unwelcome, parasitic capacitance. This capacitive effect could (due to phase shifts of the signal) affect the negative feedback of the booster in such a way that a positive feed back occurs, with the result that the booster oscillates and possibly damages the power amplifier!

The resistors (R4 and R8) effectively isolate the output of the booster from the parasitic capacitance of the output cable. They also protect the booster outputs from short circuits. We’ve used a TS922IN opamp in this booster because it can operate at very low supply voltages (the maximum is only 12 V!), but can still output a reasonable current (80 mA max.). For the supply we’ve used rechargeable batteries (e.g. NiCd or NiMH cells) so that we don’t need a mains supply.
2N3055 PDF             TDA7293 PDF             MAX232 PDF
To keep the number of cells required as small as possible, we’ve chosen a supply voltage of 5 volt; this can be supplied by four rechargeable batteries. It is also possible to use four ordinary, non-rechargeable batteries; it’s true that the supply voltage then becomes a bit higher (6 Volts), but that won’t cause any harm. Since we’ve used a symmetrical supply for the booster (2 x 2 batteries), it will be easiest if you use two separate battery holders, each with two AA cells. The two holders are connected in series.

Make sure that the batteries are connected the right way round; the positive of one always has to be connected to the negative of the next. This also applies to the connection between the two battery holders. S1A/B is a double pole switch, which is used to turn both halves of the battery supply on or off simultaneously. If you can’t ?nd the (dual) opamp we’ve used (or an equivalent), you could always use standard opamps such as the NE5532, TL082 or TL072. These do need a higher supply voltage to operate properly. In these cases you should use two 9 V batteries and replace resistor R9 with a 15 kΩ one.

Do take care when you connect the circuit to your power amplifier because the output signal can be a lot larger and you could overload the power amplifier. (Although you’re more likely to damage the loudspeakers, rather than the amplifier!) (Please note that these two 9 V batteries can’t be used as a supply for the TS922IN!) In our circuit we’ve used a stereo jack socket for the input and phono sockets for the output because these are the most compatible with MP3 players and power amplifiers respectively. If you wanted to, you could solder shielded cables directly to the circuit instead, with the correct plugs on the ends. You’ll never ?nd yourself without the correct connection leads in that case!

Experimental Pendulum Clock

Using this design, you can construct an electromagnetically impulsed pendulum clock with a 1-second beat. On the prototype, the pendulum rod is 115cm long with a bob adjusted to make it beat every second. It is suspended on a short piece of mainspring from a watch, which is attached to a vertical backboard with a 6mm screw. The rod extends some 15cm below the bob and is fitted with large washes at the lower end. Note that for a pendulum to beat in seconds, there must be 99.4cm distance between the support and the centre of mass of the pendulum. Between the bob and the lower end is a 5mm wide white reflector facing back.

Below the rod and 15mm to the left is the impulse solenoid, with a core but no actuator attached. The circuit comprises of four parts: (1) the sensor; (2) the counter and solenoid driver; (3) the clock driver; and (4) the clock. The sensor is built on its own small piece of strip board and is located on the centre line of the backboard behind the reflector. It utilises a Sharp IS471F infrared modulated detector (Farnell cat. 414-2860) to eliminate interference from external light sources. The infrared emitter (IRLED1) must be mounted near to the detector (IRDET1) but be masked from it.

The emitter radiates a coded signal toward the reflector. As the pendulum passes the centre line it reflects the signal back to the detector, which then gives a negative-going output pulse on pin 2. This makes the surface-mount LED (LED1) flash once. It also sends a signal to the counter and clock driver circuits on the main circuit board. Pulses from the sensor are fed into IC1, a 4020 14-stage ripple counter. The counter’s output (pin 6) goes high every 128 counts (seconds). These long duration pulses are inverted by transistor Q1 and differentiated by the 10nF capacitor and 22kO resistor, providing a narrow trigger pulse for a 7555 CMOS timer (IC2).

Circuit diagram:

Experimental Pendulum Clock Circuit Diagram

The 7555 is wired as a monostable, driving the base of transistor Q3 with a relatively short pulse width suitable for energising the impulse solenoid. LED2 flashes in unison with solenoid pulses, and can be mounted right on the solenoid as a visual aid. Pushbutton switch S2 is used to provide gentle starting pulses to get the pendulum swinging smoothly at the outset. Switch S1 resets the counter to zero. With this arrangement, the pendulum is set swinging and when it is to the left of centre, S1is pushed. Thus, the pendulum moves right to left on even numbered counts. At the 128th count, the solenoid gives a shot pull to the left just as the pendulum is passing through the centre line and moving right to left.

2N7002 Circuit  S8050 Circuit
The distance of the solenoid below the pendulum is adjusted so that it does not jerk the pendulum but adds a gentle nudge. The clock driver circuit also derives its timing from the output of the sensor. Negative-going pulses from the sensor are inverted by Q4 before being fed into a 4013 flipflop. On the output side, pins 12 & 13 go high in turn for one second. These pulses are too long to directly drive the clock coil, so they’re logically "anded" with the short pulses from the sensor using two gates of a 4093 NAND Schmitt trigger (IC4). The outputs from these gates then drive an adapted quartz clock movement.

A suitable clock can be made from a standard quartz movement by isolating the coil and removing the battery. See SILICON CHIP, Dec. 1996, page 38 for full instructions or October 2001 page 37 for brief notes. This is an experimental clock so you may have to try various solenoids to find one that works for you. If necessary, the solenoid pulse duration can be changed by varying IC2’s timing components. If the suspension is too stiff, try impulsing at 64 beats from pin 4 of IC1, but note that the aim is to get the freest pendulum movement possible. The Synchronome and Hipp clocks were impulsed at 30-second intervals, so your clock could be even better.

In the prototype, the reflector was made from the back of an adhesive cable clip snapped on to the pendulum rod. The white back was masked to give a 5mm wide central vertical strip, giving clean, short pulses as the pendulum passes. Current drain is several milliamps, so the prototype was powered from an SLA battery fed from a float charger. A pendulum beating in seconds is called a Royal pendulum. Its length is the same as one in a typical long case (grandfather) clock.