Circuit Diagram

PRECISE_ONE_SHOT

Published:2009/6/17 21:28:00 Author:May

This approach uses a flip-flop, a shift register, and two gates (A). Before the one-shot pulse, the output of the NOR gate is 0. Consequently, the data input of the D-type flip-flop is equivalent to the trigger. When a trigger pulse is present, the flip-flop initiates the one-shot pulse, and the n-stage shift register controls the pulse width, tw , which is a multiple of the clock's period (B).The precision of the one-shot pulse is determined by the clock period, which is inversely pro-portional to its frequency. For the circuit to work properly, the width of the trigger pulse, twt, should be greater than one clock period.The OR gate masks the trigger's effect when the circuit is generating the desired pulse. The net result is a circuit that functions as a nonretriggerable rrtultivibrator.When the pulse needs to be only one-clock-period wide, the circuit can be simplified. All that's required are two D-type flip-flops and an AND gate. However, despite its simplicity, this circuit generates a more stable and precise one-shot pulse than a multivibrator.   (View)

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LOGIC_PULSER

Published:2009/6/17 21:24:00 Author:May

The logic pulser generates pulses at 500 Hz or 0.5 Hz. When the pulser's tip connects to an in-put that is already being driven high or low, the pulser senses the logic state and automatically pulses the input briefly to the opposite state.   (View)

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PULSE_GENERATOR

Published:2009/6/17 21:21:00 Author:May

By using a 556 dual timer with IC1A acting as a waveshaper and IC1B as a pulse generator, a 10:1 range of pulse widths can be generated.A sine wave can be used to trigger this circuit.   (View)

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ADD_ON_PULSE_GENERATOR

Published:2009/6/17 21:20:00 Author:May

This pulse generator can supplement a standalone pulse generator. Using a transistor and a 555 Limer, pulse widths of <5 μs to 500 μs can be produced. The value of C3 is approximately found from Lhe formula:C3μF ≈ 1.1 x 10-5T whereT is the shortest pulse width (μs) desired in a 10:1 range(T should be greater than 5 μs)The capacitor values and consequent pulse width range are shown.   (View)

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PROXIMITY_ALARM_II

Published:2009/6/17 21:10:00 Author:May

A CMOS logic gate is used to make up this circuit. When an object is near the antenna, the change in oscillator output is detected by D1 and D2 and amplified by U1C, which drives Q1, sound-ing alarm BZ1.   (View)

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PROXIMITY_ALARM_I

Published:2009/6/17 21:08:00 Author:May

IC1 contains several oscillators and an amplifier. The low-frequency audio-signal oscillator is used to supply an input to the amplifier. That signal is the audio tone that is amplified, then supplied to the speaker by the amplifier.The high-frequency oscillator is purposely set to be very unstable. It is dormant or off until the resistor-capacitor (RC) network is changed. The resistance (fi) in this case is made up of R2 and P1. As the resistance of Pl is decreased, the unit becomes more sensitive (more unstable), and less ca-pacitance (C) is needed to cause the oscillator to oscillate.The capacitance required is provided by C2 and by any capacitance introduced via the antenna loop. When you come near that loop, your inherent body capacitance causes the high-frequency os-cillator to begin to oscillate, which then causes the low-frequency oscillator to be switched on in-ternally. Once the alarm is sounding, the IC is designed so that it latches , that is, it stays on until the power to it is switched off.C1 1-pFAxialCapacitorC2 27-pF Silver Mica CapacitorC3 0.1-pF Mylar CapacitorIC1 CM1001N ICP1 50-kQ Trimmer ResistorR1 75-kQ ResistorR2 200-Q ResistorR3 100-kQ ResistorS1 SPDT SwitchSpk Small SpeakerMisc IC Socket, Battery Snap, Ground Plate, Wire, PC Board   (View)

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SIMPLE_SAFETY_CIRCUIT

Published:2009/6/17 21:05:00 Author:May

The simple two-hand safety-control switch shown here is little more than two pushbutton switches connected in series; both must be de-pressed in order to energize the relay.   (View)

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LOUDSPEAKER_PROTECTOR

Published:2009/6/17 21:04:00 Author:May

Transistors Q1, Q2, and Q3 monitor the two outputs of the stereo amplifier. If the offsets exceed ±2 V, Q7 is turned off, which turns off Q8 and the normally on relay. Diodes D2 and D5, together vith Q4, provide a mains voltage monitor. As soon as the ac input voltage disappears, as when the ampli-fier is turned off, Q4 turns off and Q5 turns on. This turns off Q7, Q8, and the relay. Hence, the loud-speakers are disconnected immediately after the amplifier is turned off.   (View)

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EAR_PROTECTOR

Published:2009/6/17 21:02:00 Author:May

The ear protector is actually a peak audio- detector/shutdown circuit that disables the amplifier through its chip-disable input when the output volume of an amplifier reaches the set level. The cir-cuit, although intended for the MC34119 amplifier, should work with similar IC devices or applications.   (View)

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MODEM_FAX_PROTECTOR_FOR_TWO_COMPUTERS

Published:2009/6/17 21:01:00 Author:May

This modem/fax protector can be used in telephone-line connections betweenaPC or a terminal and a distant computer. In this circuit, the SVPs (surge voltage protectors) are at 230V.A good ground is a must for effective operation.   (View)

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TIMED_SAFETY_CIRCUIT

Published:2009/6/17 20:57:00 Author:May

When S1 is closed, pin 9 of U1 goes low, turning on Q1 for a preset period. If S2 is closed during this period, Q2 is turned on for a preset period. R11 and R13 set the two time periods.   (View)

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OVERVOLTAGE_PROTECTION_CIRCUIT

Published:2009/6/17 20:55:00 Author:May

When testing a circuit, a source of voltage that is variable and has overvoltage shutdown is very useful. In this circuit, R1 is adjusted to 1 to 2 V below the eventual shutdown threshold. R2 sets the trip voltage. When this voltage is reached, the circuit shuts the voltage to the circuit under test down. To reset, reduce R1 below trip threshold and depress reset switch S1.   (View)

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MODEM_PROTECTOR

Published:2009/6/17 20:51:00 Author:May

This protector uses surge voltage protectors rated at 230-V breakdown. An effective ground should be used.   (View)

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RELAY_FUSE_FOR_POWER_SUPPLIES

Published:2009/6/17 20:45:00 Author:May

A method of adding overload protection to a power supply using a relay is shown. In each cir-cuit, the relay must be reset by a momentary switch using a charge on capacitor C2. This prevents overload ifthe short still exists.   (View)

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OVERLOAD_INDICATOR

Published:2009/6/17 20:42:00 Author:May

Two op amps are used as comparators to indi-cate excessive magnitude of an AP signal, either positive or negative, even if the signal is asymmet-rical. P1 sets the reference voltage for both op amps. This circuit is useful for audio-amplifier and op-amp circuits using split power supplies.   (View)

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SAFETU_CIRCUIT

Published:2009/6/17 20:41:00 Author:May

Because of the finite hold-on time of delay circuits R1/C1 and R2/C2, both S1 and S2 must be pressed at the same time to power up the load.   (View)

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ELECTRONIC_FUSE

Published:2009/6/17 20:39:00 Author:May

Basically, this circuit is an adjustable electronic circuit breaker, containing a toroidal transformer Lhat senses 60-Hz load current. T1 has a two-turn winding for primary, and 100 turns of #30 gauge wire for the secondary. A high-low range switch selects 0.1 to 6 A or 1 to 12 A. The primary winding of T1 carries fuL load current and voltage; should be suitably insulated, as should be RY1.   (View)

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SPEAKER_PROTECTOR

Published:2009/6/17 20:36:00 Author:May

Most of the transistors in this speaker protector function as switches. Normally, Q4, Q5, and K1 are on and the speakers are connected to the amplifier. However, if a large dc voltage appears at an amplifier output, either Q3, or Q1 and Q2 turn on; biasing Q4 off. That action turns Q5 off, de-ener-gizes the relay, and disconnects the speakers from the amplifier. Components D1, D2, and Q6 form the overdrive-protection circuit.   (View)

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dc_dc_CONVERTER_CIRCUIT_WITH_33_V_AND_5_V_OUTPUTS

Published:2009/6/17 4:35:00 Author:May

Input voltages can range from 8 V to 30 V. The load range on the 5 V is 0.05 A to 5 A while the 3.3-V load range is 0.1 A to I A. The circuit is self-protected under no-load conditions. Over all load and line conditions, including cross regulation, the 3.3-V output varies from 3.25 V to 3.27 V. The 5-V output varies from 4.81 Y to 5.19 V under the same conditions.In a typical application to 0.5 A on the 3.3 V and 0.25 A on the 5 V, efficiency is typically 76%. With an input voltage of 30 V and a full-load condition, the efficiency drops to 66%. In normal oper-ating regions, efficiency is always better than 70%. The 5-V ripple is less than 75 mV and the 3.3-V ripple less than 50 mV over all line and load conditions.   (View)

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TEMPERATURE_COMPENSATED_ONE_QUADRANT_LOGARITHMIC_CONVERTER

Published:2009/6/17 4:33:00 Author:May

A logarithmic converter used to produce an output voltage that is proportional to the logarithm of an input current is shown. RS is the input impedance of the input source.   (View)

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