Wide Range Current Pumps for Precision PLL

The wide-range current pump for the precision phase locked loop circuit is a “semiprecision” circuit, and provides an output current proportional to -V1, give or take 10 or 15%, over a 3-decade range. The 22 MW resistors prevent the current from shutting off in case -V becomes positive (probably unnecessary if A4 is used). For best results over a full 3-decade range (11 kHz to 9 Hz), do use A4, delete the four 22 MW resistors, and insert the (diode parallel to the 470 kW) in series with the RG as shown. This will give good stability at all frequencies (although stability cannot be extended below 1/1500 of full scale without extra efforts).? This is a picture schematic:

A5, A6, ARE LF351 OR 1/2LF353 OR SIMILAR
Q5, Q6, Q7, Q9 ARE 2N2907 OR 2N3906 OR SIMILAR
Q8, Q10 ARE Q8 IS 2N3565 OR 2N3904 OR SIMILAR

This PLL has been widely used in testing of VFCs, as it can force the LM331 to run at a crystal-controlled frequency (established as the F input), and the output voltage at VOUT is promptly measured by a 6-digit (1 ppm nonlinearity, max) digital voltmeter, with much greater speed and precision than can be obtained by forcing a voltage and trying to read a frequency. While at 10 kHz, the advantages are clearcut; at 50 Hz it is even more obvious. Measuring a 50 Hz signal with ±0.01 Hz resolution cannot be done (even with the most powerful computing counter-timer) as accurately, quickly, and conveniently as the PLL’s voltage output settles.
Source circuit : http://www.hqew.net/circuit-diagram/Wide-Range-Current-Pumps-for-Precision-PLL_2952.html

How RS232 works

This section describes how RS232  works in general without describing complex handshake methods – only the simplest system is described – this it the most useful and the most likely to work!. Data is transmitted serially in one direction over a pair of wires. Data going out is labeled Tx (indicating transmission) while data coming in is labeled Rx (indicating reception). To create a two way communication system a minimum of three wires are needed Tx, Rx and GND (ground). Crossing over Tx & Rx between the two systems lets each unit talk to the opposite one. Each byte can be transmitted at any time (as long as the previous byte has been transmitted). The transmitted byte is not synchronized to the receiver – it is an asynchronous protocol i.e. there is no clock signal. For this reason software at each end of the communication link must be set up exactly the same so that each serial decoder chip can decode the serial data stream.

Note: The? signal level inversion (logic 1 is -12V and logic 0 is 12V).

How RS232 works : Baud

This is simply the transmission speed measured in bits per second. It defines the frequency of each bit period.? For a baud rate of 2400 (2400 bps) the frequency is 2400Hz and the bit period is 1/2400 or 416.6us. This is the information that a receiver uses to recover the bits from the data stream.

How RS232 works : Voltage levels

Transmitter

How RS232 works when transmitting a data bit stream. To make it work over long cables high voltages are sent from each transmitter since due to cable resistance the voltage reduces the further the signal has to travel. The output voltage specification isfrom 5V to 25V (transmitting a logical zero) and -5V to -25V (transmitting a logical one).? Note: all signals in the cable have to generate the same voltage levels e.g. DTR, DSR, RTS, CTS. So you need a lot of level translator chips for a full interface but for very short distances you only need TX and RX and ground.? The receiver can accept minimum signal levels of? 3V.? The maximum voltage of 25V does not have to be used and a common voltage in use is 12V (output by MAX232 transceiver chip).? A mark (logical one) is sent as -12V and a space (logical zero) is sent as 12V i.e. the logic sense is inverted. Note: The fact that high voltages exist at the serial port allows powering devices that you would not normally expect to find on it. But they must draw very little current.

Receiver

How RS232 works when receiving a data bit stream.? At the receiver the input voltage levels are defined as ?3V i.e. to receive a logic zero the voltage must be greater than 3V and to receive a logic one the voltage must be smaller than -3V. This allows for losses as the signal travels down the cable and provides noise immunity i.e. any spurious noise up to a level of ?3V can be tolerated without it having any effect on the receiver.

How RS232 works :? Bit stream

How RS232 works – the Start Bit. The protocol is described as asynchronous as there is no clock transmitted at all. Instead a different method of clock recovery is used.? At the beginning of each transmission a start bit is transmitted indicating to the receiver that a byte of data is about to follow.? The start bit lets the receiver synchronize to the data bits. What this means is that the receiver can create its own sample clock at the middle of each bit. Note that once the start bit is found the receiver knows where the following bits will be as it is given the sample period (derived from the baud rate) as part of the initialization process.

How RS232 works – the Data bits

Data bits follow the start bit. There will be seven or eight data bits with the lsb transmitted first. The reason you can choose between seven or eight is that ASCII is made up of the alphabet within the first seven bits (as well as the control characters). The eighth bit extends the character set for graphical symbols.? If you only want to transmit text then you only need 7 bits. This saves a bit and increases transmission speed when transmitting large blocks of data. Other data bit sizes are 5 and 6 bits.? However bit length is usually ignored and a transmission size of 8 bits is commonly used.? Note: If you use RS232 to transmit raw data (binary data) then you will need 8 data bits.

How RS232 works – the Parity Bit

The parity bit is a crude error detection mechanism. You can use either odd parity or even parity or none at all (in this case no parity bit is transmitted).? It simply evaluates all the data bits and for odd parity returns a logic one if there is an odd number of data bits that are set. For even parity an even number of data bits that are set, sets the parity bit.? At the receiver the parity bit is used to tell if an error occurred during transmission. You can use this in the receiver software by reading a flag in the UART module.? The problem with error detection using the parity bit is that if two bits are in error then the parity check fails. This is because each error cancels the effect of the other (in terms of the parity calculation). Any even number of errors causes a failure in error detection. It won’t be a problem on a bench top based system (that has no critical data transfer). Over a short cable e.g. 6ft you probably won’t see any errors anyway. Normally I use no parity and there is no problem at all.? For systems running over a long distance or in a noisy environment a better system should be used e.g. Adding a cyclic redundancy check to the data stream before and after it is sent over the RS232. CRCs let you check for and correct quite a few errors without re transmitting the data.

How RS232 works – the Stop bit

The stop bit merely gives a period of time before the next start bit can be transmitted. It is the opposite sense to the start bit and because of this allows the start bit to be seen.? If there was no stop bit then the last bit in the data stream would be the parity bit (or data bit if parity is not active). This would change depending on the data sent so if it had the same sense as the start bit then the start bit could not be seen. The stop bit can be set choosing from 1, 1.5, or 2 bit periods.

How RS232 works :? Typical Settings

Typical settings for use on the desktop e.g. between a microcontroller and hyperterminal:

Hardware Connections 3 (Rx,Tx,GND) – Rx and Tx crossed over.

Signals : How RS232 works with signal levels? At some point you may want to make a software UART perhaps to save code space in your current design (maybe you don’t need the receive part – just outputting variables) or to use a spare pin or perhaps your provider’s library does not work.? Note: you can find receive and transmit software USART code in the 12F675 Tutorial pages.? To create it you need the actual signal diagrams that you see at the microcontroller pin (strangely these are hard to find on the web).? The following diagram shows how RS232 works by generating 0-5V logic bit stream at the output pin of the microcontroller or UART followed by the translated voltages that are transmitted to the serial cable. These are generated by sending the 0-5V logic levels to a transceiver chip e.g. MAX232. which can use a 5V power supply and boost it to the required 12 volts.? How RS232 works when transmitting a character

source: http://www.hqew.net/circuit-diagram/How-RS232-works_2956.html

10 Watt Stereo Amplifier Circuit Using TDA2009A

This circuit is a circuit diagram amplifer. This amplifier circuit has a power of 10 watts. This amplifier circuit is very suitable to apply to your car audio. This amplifier using IC TDA2009A,  as amplifeir power. To avoid excessive heat in the IC using some heat sink compound between the heat sink & the IC. C1 & C2 is the input coupling capacitor and blocks DC, as well as C10 & C11 which is the output capacitor Kopel, and C6 & C7 which blocks the DC from the feed back loop. R1/R2 (and R3/R4) Set the level of feedback. The following is a schematic drawing:

Get together with 1 (R1/R2) = 68 or 37 dB. C8/R5 (and C9/R6) provides high frequency stability where loudspeaker inductive reactance load can become excessive. C4 and C5 provide power decoupling or filtering. Absolute maximum supply voltage is 28V for the amplifer.

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Long Time Comparator

This circuit is a series of long-time comparator. As a comparator to use IC LM106. Long-time comparator circuit uses 2N4393 JFET is operated as a Miller integrator. The high Yfs 2N4393 (more than 12,000 mmhos @ 5 mA) produced a profit of about 60 stages. Because the gate capacitance is equivalent to look to the time the C gain and resistance sources can be as high as 10 MOhm gate, the time constant for one minute can be achieved. Here is a schematic drawing:

Source: http://www.hqew.net/circuit-diagram/Long-Time-Comparator_2935.html

Toggle Flip Flop Laser Pointer Using CD4013

The circuit below is similar to the one above but can be used with a laser pointer to toggle the relay rather than a push button. The IR photo transistor Q1 (Radio Shack 276-145A) or similar is connected to the set input (pin 6). The photo transistor should be shielded from direct light so that the voltage at the set input (pin 6) is less than 1 volt under ambient conditions and moves to more than 10 volts when illuminated by the laser pointer or other light source.

The reset time is about a half second using a 4.7uF cap which prevents the circuit from toggling more than once during a half second interval. The 10K resistor and diode provide a faster discharge path for the 4.7uF cap so the circuit can be retoggled in less than 1 second. The 3K resistor in series with the photo transistor may need be adjusted for best performance. The relay shown is a solid state variety to be used with lights or other resistive loads at less than 3 amps. A mechanical relay can also be used as shown in circuit above.

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Closed Loop PWM Motor Control

Closed loop (servo) control is used to make a constant speed motor control. Constant speed means that the speed of the motor will be kept constant although the load is change, or even when the electric supply voltage is also changed. The circuit maintain the speed at a constant value by sensing the actual speed using a tachometer. If the speed is slowing down because of the load become harder, or because the electric supply get slightly lower, the circuit will automatically increase the power transfer to the motor by increasing the duty cycle of the motor drive, until the sensed speed by the tachometer and the reference speed has no difference.

Motor Control Circuit

The circuit is unipolar, means that you cannot change the motor direction by the control signal. This switched mode motor drive (SMMD) uses NE5560 as the core of the circuit, suitable for small DC motor. The power switching component is a single Philips BUK456-100A Power MOSFET. It has current handling capability over 30 A, and 100 V voltage rating of VDS, and 0.057 Ohms RDS-ON. The nominal frequency of the PWM is 10 KHz, but much higher frequency is possible. It is also a good idea to operate the switching over 20 KHz to avoid audible interference to audio equipments. VGS, the peak gate to source voltage, is 15V to ensure minimum RDS(ON), so the power loss in the PowerMOS switch is minimum.

Torque Limiter

This circuit include a current sense resistor, placed in the source lead to monitor motor drive current on a cycle-by-cycle basis.This resistor value is set to produce the error amplifier threshold voltage at the desired maximum current. When this threshold voltage is exceeded, the NE5560 then automatically limits the duty cycle of the PWM output. You can say this is a torque limitter feature, which is actually an unavoidable effect of the switching device protection by limiting the current.

Motor Start-Up and Dynamic Braking

At power on, to avoid power surge, a slow start network (Pins 2,5,6) gradually ramps up the duty cycle. Forcing the input of the error amplifier By K1B produce a fixed duty cycle control for braking. The over-current circuit still work during braking. [Circuit schematic diagram source: Power Semiconductor Applications from Philips Semiconductors]

 

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Electronic Metronome

Metronome is very important tool if you studying music playing. There are mechanical metronome device in the past, but today, electronic metronome is much more popular since it can be very simple, compact/small, reliable, and also has the most interesting feature: cheap. Here is one example of the electronic metronome schematic:

Parts:

• C1 1 uF 63V Polyester Capacitor
• C2 10nF 63V Polyester Capacitor
• C3 47 uF 25V Electrolytic Capacitor
• R1 10K 1/2W Trimmer Cermet
• R2 10K 1/4W Resistor
• R3 330K 1/4W Resistor
• R4 50K 1/2W Trimmer Cermet
• R5 100K 1/4W Resistor
• R6,R7 1K 1/4W Resistor
• P1 100K Linear Potentiometer
• SW1 SPST Switch (Ganged with P1)
• SPK 8 Ohm 40mm. Loudspeaker
• B1 12V Battery (MN21, GP23A or VR22 type)
• IC1 NE555 General purpose timer IC
• Q1,Q2 BC560 45V 100mA Low noise High gain PNP Transistors
• Q3 ZTX753 100V 2A PNP Transistor

A variable current source is built around Q1 and Q2, this provides linear scale that can be directly mapped to the potentiometer position. Transistor Q3 is employed to amplify the signal to get louder click sound, similar to clockwork metronomes. To obtain more output power and more compact package, a 12V micro battery was used.? Don’t worry if you can’t get the battery since it works also for 9V battery.? Rotate P1 fully towards R2, then set R1 to obtain 40 beats per minute (compare with another metronome). Rotate P1 fully towards R3, then set R4 to obtain 208 beats per minute.

Finally mark the entire scale with the common metronome steps as following:
40 – 42 – 44 – 46 – 48 – 50 – 52 – 54 – 58 – 60 – 63 – 66 – 69 – 72 – 76 – 80 – 84 – 88 – 92 – 96 – 100 – 104 – 108 – 112 – 116 – 120 – 126 – 132 – 138 – 144 – 152 – 160 – 168 – 176 – 184 – 192 – 200 – 208. [Circuit's schematic diagram source: http://www.hqew.net/circuit-diagram/Electronic-Metronome_2901.html]