MICROMETRONOME

Published:2009/6/25 21:04:00 Author:May

This compact metronome will run for years on a single nine-volt transistor battery.Has both tone and pulse rate controls, and uses touch plates to start and stop, can be built in a case no larger than a pack of cigarettes. The touch plates consist of two strips of metal about 1/16-inch apart mounted on, but insulated from, the case. Bridging the gap closes the switch.   (View)

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STEREO_REVERB_SYSTEM

Published:2009/6/25 21:04:00 Author:May

The LM378 dual power amplifier is used as the spring driver. The recovery amplifier is a low noise dual preamplifier. Mixing of the delayed signal with the original is done with another LM387 used in an inverting summing configuration.   (View)

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LONG_TIME_DELAY

Published:2009/6/25 21:02:00 Author:May

Circuit NotesIn the 556 timer, the timing is a function of the charging rate of the external capacitor. For long time delays, expensive capacitors with extremely low leakage are required. The prac-ticality of the components involved limits the time between pulses to something in the neighborhood of 10 minutes. To achieve longer time periods, both halves of a dual timer may be connected in tandem with a Divide-by ' net-work in between the first timer section oper-ates in an oscillatory mode with a period of 1/fo. This signal is then applied to a Divide-by-N network to give an output with the period of N/fo. This can then be used to trigger the second half of the 556. The total time delay is now a function of N and fo.   (View)

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MUSIC_SYNTHESIZER

Published:2009/6/25 20:57:00 Author:May

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FET_CURVE_TRACER

Published:2009/6/25 20:34:00 Author:May

The circuit displays drain current versus gate voltage for both P and N-channel JFETS at a constant drain voltge.   (View)

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GEIGER_COUNTER

Published:2009/6/25 5:13:00 Author:May

The Geiger tube needs a high voltage sup-ply which consists of Q1 and its associated components. The transformer is connected in reverse; the secondary is connected as a Hartley oscillator, and RI provides base bias.Dl, D2, C4, and C5 comprise avoltage doubler.RV1 should be set so that each click heard is nice and clean because over a certain voltage range all that will be heard is a continuous buzz.   (View)

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SENSITIVE_GEIGER_COUNTER

Published:2009/6/25 5:11:00 Author:May

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GAMMA_RAY_PULSE_INTEGRATOR

Published:2009/6/25 5:10:00 Author:May

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DC_TO_DC_SMPS_USING_NE5561_VARIABLE_18_V_to_30_V_OUT_AT_O2_A

Published:2009/6/25 4:32:00 Author:May

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DC_TO_DC_AC_INVERTER

Published:2009/6/25 4:28:00 Author:May

Circuit Notes This inverter uses no special components such as the torodial transformer used in many inverters. Cost is kept ldw with the use of cheap, readily available components. Essen-tially, it is a power amplifier driven by an asta-ble multivibrator. The frequency is around 1200 Hz which most 50/60 Hz power transfor-mers handle well without too much loss. In-creasing the value of capacitors C1 and C2 will lower the frequency if any trouble is experi-enced. However, rectifier filtering capacitors required are considerably smaller at the higher operating frequency. The two 2N3055 transis-tor should be mounted on an adequately sized heatsink. The transformer should be rated ac-cording to the amount of output power required allowing for conversion efficiency of approxi-mately 60%.   (View)

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AUDIO_RF_SIGNAL_TRACER_PROBE

Published:2009/6/25 4:24:00 Author:May

This economical signal tracer is useful for servicing and alignment work in receivers and low power transmitters. When switched to RF, the modulation on any signal is detected by the diode and amplified by the FET. A twin-core shielded lead can be used to connect the probe to an amplifier and to feed 6 volts to it.   (View)

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PRECISION_CURRENT_SINK

Published:2009/6/25 4:18:00 Author:May

Circuit Notes The 2N5457 JFET and PN2222 bipolar have inherently high output impedance. Using R1 as a current sensing resistor to provide feedback to the LM101 op amp provides a large amount of loop gain for negative feedback to enhance the true current sink nature of this circuit. For small current values, the 10 K re-sistor and PN2222 may be eliminated if the source of the JFET is connected to R1.   (View)

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SIMPLE_LOGIC_PROBE

Published:2009/6/25 4:17:00 Author:May

If the probe is connected to logic 0, Q1 will be turned on lighting D1. At logic 1, Q2 will be turned on lighting D2. For Q1 and Q2 any NPN or PNP transistors will do.Similarly, D1 and D2 can be any LEDs.   (View)

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1AND_GATE

Published:2009/6/25 3:18:00 Author:May

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LARGE_FAN_IN_AND_GATE

Published:2009/6/25 3:18:00 Author:May

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R_S_FLIP_FLOP

Published:2009/6/25 3:17:00 Author:May

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1OR_GATE

Published:2009/6/25 3:17:00 Author:May

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AND_GATE

Published:2009/6/25 3:15:00 Author:May

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OR_GATE___

Published:2009/6/25 3:14:00 Author:May

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LOGIC_PROBE_1

Published:2009/6/25 4:15:00 Author:May

The probe indicates a high or low at 70% and 30% of V+ (5 to 12 V). One section of the voltage comparator (LM393) senses V in over 70% of supply and the second section senses V in under 30%. These two sections direct-drive the appropriate LEDs. The pulse detector is a CMOS oneshot (MC14538) triggered on the rising edge of the LM393 outputs through 1N4148 diodes. With the RC values shown, it triggered reliably at greater than 30 kHz on both sine and square waves.   (View)

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