Circuit Diagram

WWV_CONVERTER

Published:2009/6/22 23:37:00 Author:May

This converter heterodynes the 15-MHz WWW signal with a 16-MHz oscillator so that it can be heard at 1 MHz on an ANI broadcast receiver. T1 and T2 are a modified 10.7-MHz IF transformer and AM BO oscillator coil, respectively.   (View)

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AUDIO_VOLUME_LIMITER

Published:2009/6/22 23:49:00 Author:Jessie

In this circuit，amplifier IC1-a provides signal amplification of 40 to＋40 dB depending on thevalue of the LDR The LDR(ight dependent resistor)is driven by rectified audio from voltage follower IC1b and bridge rectifier D1 through D4   (View)

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PSEUDOGROUND

Published:2009/6/22 23:37:00 Author:May

For op-amp circuits, a pseudo ground is often needed; a voltage reference IC can be used. The Analog Devices AD780 is used here for this application. This can sink or source current.   (View)

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BLOWN_FUSE_ALARM

Published:2009/6/22 23:49:00 Author:Jessie

If the fuse blows, the LED indicator starts to blink.   (View)

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LOW_FREQUENCY_ASTABLE

Published:2009/6/22 23:49:00 Author:Jessie

By using a high-gain low-current transistor, such as the 2N3565, a pair of Darlington-connected transistors (2N3565 and 2N3904) can be used in a high-impedance configuration.   (View)

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SINGLE_CHIP_MESSAGE_SYSTEM

Published:2009/6/22 23:35:00 Author:May

The ISD1016 is a complete analog audio record/playback system on a chip. The analog signal is sampled and the samples stored in an EEPROM as analog levels. Upon playback, the analog data is read out and amplified. Up to 16 seconds of data(audio)can be stored.   (View)

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AUTOMOTIVE_BURGLAR_ALARM

Published:2009/6/22 23:35:00 Author:May

Alarm triggers on after a 13 second delay and stays on for 1-1 1/2 minutes. Then it resets automatically. It can also be turned off and reset by opening and reclosing S1.   (View)

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The low-noise and high-efficiency PWM step-down converting power supply circuit

Published:2011/7/24 3:29:00 Author:Seven | Keyword: low-noise, high-efficiency, power supply

In the figure is the adjustable step-down power supply which is based on the low-noise and high-efficiency PWM converter MAX887(8-SO package), and the external elements are few. The characters of it are: (1) the input voltage is from 3.5V to 11.5V, the output voltage is 1.25V to 10.25V; (2) the output current is 600mA, and the static current is 200μA, the standby mode is only 2.5μA; (3) the converting efficiency is 95%; (4) the fixed working frequency of MAX887 is 300KHZ, which effectively reduces the size and cost of the external element.   (View)

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AUDIBLE_CONTINUITY_TESTER

Published:2009/6/22 23:35:00 Author:May

  (View)

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The +5V solid output step-down convert power supply circuit composed of MAX639

Published:2011/7/24 2:13:00 Author:Seven | Keyword: step-down, power supply

In the figure is the +5V solid output step-down convert power supply circuit composed of MAX639. MAX639 is a high-power step-down DC/AC converter. The input voltage ranges from 5.5V to 11.5V, the output is the +5V solid voltage or the adjustable voltage, the output current is 100mA, the converting efficiency is higher than 90%. The circuit has the function of low battery voltage detection and working/disable mode control.   (View)

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CURRENT_REGULATOR_OP_AMP

Published:2009/6/22 23:35:00 Author:May

  (View)

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SIMPLE_AUDIO_VIDEO_CABLE_TESTER

Published:2009/6/22 23:34:00 Author:May

As simple as it looks, the audio/video cable tester tests cables while they are plugged in. You can flex them vigorously while listening to the built-in buzzer.Simply plug the ends of the cable in the appropriate jack. Only one end of the cable need be plugged in for a complete short test; the other end is left free. If the buzzer sounds, there is a short circuit somewhere in the cable. If nothing is heard, test for an intermittent short by flexing the cable several times, particularly in the plug area of both the free and plugged-in ends.   (View)

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SINGLE_SUPPLY_OP_AMP_APPLICATIONS

Published:2009/6/22 23:34:00 Author:May

An op amp that normally needs two supplies can be used when only a single supply is needed. The value of V+ should be twice the minimum allowable values of the positive and negative voltages normally needed. For example, a 12-V single-supply application would require an op amp capable of ±6-V operation.   (View)

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The 20W switch DC voltage stabilizing power supply circuit

Published:2011/7/24 2:05:00 Author:Seven | Keyword: DC voltage, power supply

The technique indicators of the power supply are shown as follows:AC input voltage range: u=85～265V; input grid frequency: fLl=47～440Hz; Output voltage (Io=1.67A): Uo=12V;MAX output power: IOM=1.67A; Continuous output power: Po=20W(TA=25℃ or 15W(TA=50℃);Voltage adjusting ratio: η=78％; Output wave voltage MAX value: ±60mV; Working temperature range: TA=0～50℃.   (View)

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ADJUSTABLE_CONTINUITY_TESTER

Published:2009/6/22 23:34:00 Author:May

A problem with most continuity testers is that the exact decision point (circuit resistance) be-tween continuity and open is indefinite. This circuit allows setting of this point to a known resistance between 1 and 50Ω.   (View)

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VOCAL_STRIPPER_POWER_SUPPLY

Published:2009/6/22 23:33:00 Author:May

The power supply schematic for the lead vocal filter circuit.   (View)

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SHORT_CIRCUIT_BEEPER

Published:2009/6/22 23:33:00 Author:May

This design offers a way to trace resistance in the milliohm range, right to a short between bridged traces beneath a solder mask. It simply translates resistance into an audible tone, which in-creases in pitch as the measured value approaches zero.In the classic op-amp multivibrator (shown in the inset), oscillation frequency is determined not only by the R1/C1 time constant, but also by the hysteresis set by the R2/R3 resistance ratio. Al in the main figure, with current boosters Q1 and Q2, is this same configuration.Assuming a virtual ground at the output of A2, free-run frequency is about 1 kHz-quite audible through a tiny 8-Ω speaker. Q1 and Q2 deliver a ±10-V squarewave to R4, dumping a ±100 mA through a short circuit placed across the probe tips. R5 ensures that open circuit voltage never ex-ceeds ±0.1 V.AZ monitors the voltage between the probes. The differential input must have its own separate path to the probe tips to eliminate test lead resistance from the measurement. Miniature zip-cord sold as loudspeaker wire makes a tidy two-conductor test lead.When the probes are open, A2's gain equals the R4/R5 divider loss, and the output of both am-plifiers is identical. This has two effects: first, hysteresis is greatly increased and the frequency falls to a low growl; second, the loudspeaker that bridges the two in-phase outputs is effectively silenced.The dead short across the probe tips will return nothing to AZ and the circuit will squeal at its nominal 1-kHz rate. Anything less than a perfect short produces some output from A2, increasing multivibrator hysteresis and lowering the pitch. The circuit has so much 'leverage, and the ear is so sensitive to pitch changes in this range, that it's easy to resolve minute resistance differences.Any general-purpose op amp will suffice in this circuit-a couple of 741s or an equivalent dual.   (View)

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PARALLELED_POWER_OP_AMPS

Published:2009/6/22 23:30:00 Author:May

Two power op amps can be paralleled using this master/slave arrangement, but high-requency performance suffers.   (View)

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VOCAL_STRIPPER

Published:2009/6/22 23:29:00 Author:May

The schematic of the lead vocal filter is shown in the figure. The left and right channel signals are coupled through C1 and'C2 to buffer amps IC4-a and IC4-b. From the buffer amps, the left and right channel signals pass through active crossovers IC5-a and IC5-b, sending all low frequencies to a final mixer IC6-c, and all middle and high frequencies to analog delay lines IC1 and IC2, RD5106256-sam-ple bucket-brigades. Integrated circuit IC2 delays the left-channel signal by 2.4 ms, set by the fixed-frequency clock generated by 1/2IC3, R47, and C24. The right channel signal is delayed by IC1 with a variable-frequency clock generated by 1/2IC3, R48, R49, and C23. Potentiometer R49 is used for phase adjustment.The output of each delay line from IC1 and IC2 passes through low-pass filters IC6-a and -d, and their associated parts, to filter out high-frequency sample-steps produced by IC1 and IC2. Balance control R36 is adjusted for equal amplitude of the left and right channels. ICG-b is a difference am-plifier that cancels all lead vocals that are common to both channels. The resulting signal from ICG-b is remixed with low frequencies by ICG-c and is then sbnt to the output via buffers IC4-c and IC4-d.   (View)

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ENHANCED_OP_AMP_BALANCED_AMPLIFIER

Published:2009/6/22 23:29:00 Author:May

The classic single op-amp balanced circuit works well in low-source-impedartce configurations, but tends to struggle in higher-source-imp edance applications because of the varying input impedance of the inputs referred to ground. A modified version of the classic op-amp configuration of the figure uses a different set of formulas to determine the resistor values. It equalizes the impedance of both inputs by considering the op amp's active participation.   (View)

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