Circuit Diagram

COUNTING_RATE_METER

Published:2009/7/13 4:49:00 Author:May

Uses three Optical Electronics 9827 opamps to amplify, square up, and integrate input pulses from event detector, to give integrated DC voltage that is function of counting rate. This voltage is compressed by 2538 DC logamp having 60-dB dynamic range for driving chart recorder. Values of R and C de-pend on counting rate, Well-regulated power supply is required because this determines am-plitude of squared pulses that drive integrator. Applications include counting photons of photomultiplier or nuclear particles of solid-state detector. Logamp compresses output of integrator to eliminate need for scale changing while giving constant accuracy over wide dy-namic range of counting rates. - Logarithmic Counting Rate Readout, Optical Electronics, Tucson, AZ, Application Tip 10106.   (View)

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LAMP_SURGE_SUPPRESSOR

Published:2009/7/13 4:48:00 Author:May

Circuit limits turn-on current through cold filament, which is major cause of lamp failure but provides normal current when filament reaches operating temperature. Developed primarily for use with lamps in locations where replacement is extremely difficult. Values shown a re primarily for low-voltage pilot lamps such as No. 44 and No.47 but can be applied to any lamp within voltage and current ratings of transistors used,-J. A.Sandier, 11 Projects under $11, Modern Electronics, June 1978, p 54-58.   (View)

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2_m_TO_BROADCAST_BAND

Published:2009/7/16 3:52:00 Author:Jessie

Permits tuning to 2-m (146-MHz) amateur band with ordinary AM auto radio, for monitoring FM repeaters and other 2-m amateur stations. Article stresses importance of shielding, compartmentalization, and RF blocking along power lead to prevent bleed-through of broadcast stations. Separate 9-V battery gives long life if converter is turned off when not in use, because drain is only 25 mA. L2 is 4 turns No. 20 on 7-mm slug-tuned form, with 2-turn link L1 at low end and tap 11/2 turns from low end. L3 and L4 are 3 turns No. 20 on 7-mm slug-tuned form. L5 is 20 turns No. 30 on 4-mm solid ferrite form. Y1 is 48.5-MHz third-overtone crystal. Convener gives good reception of both AM and FM stations on 2 m, with sharpness of receiver IF tuning determining ability of radio to slope-detect FM signals.-J. R. Johnson, New Improved Repeater Monitor, 73 Magazine. Dec. 1976, p 106-109.   (View)

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CAR_PRESENCE_DETECTOR

Published:2009/7/13 4:48:00 Author:May

Here's a circuit that will, if calibrated carefully, detect the presence of a large metal object. Coil L1 is made by winding 50 turns of 26-gauge wire on a 50-inch form. If L1 is buried in the ground, the circuit can be used to detect any car or truck that is driven over the coil. Transistor Q1 and its surrounding components make up a Coipitts oscillator, operating at 10 kHz. The output is coupled to a Maxwell bridge through the secondary of T1, which is a 600-Ω-to-600-Ω audio coupling transformer. With R1, R2, and R3 set properly, the bridge is balanced when no metal is close to L1, producing a near-zero ac signal at the bridge's output (the R5/L1 junction and ground). Should a large enough ferromagnetic object pass over L1, the bridge becomes unbalanced, producing a signal at the junction of R5 and L1. That signal is fed to the base of Q2, part of a common-emitter amplifier stage. Resistor R4 adjusts to the gain of that stage. The signal from the amplifier is fed to the base of Q3, which drives a voltage doubler that supplies current to the relay driver, Q4. The relay, K1, is a 1000-Ω, sensitive, 12-V unit that can drive a normally open or closed alarm circuit to indicate the presence of a vehicle. Use shielded cable to attach L1 to the circuit, and do not bury L1 deeper than 8 inches for best results. Remember to weatherproof all components that will reside outside.   (View)

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CHOPPER_FOR_IC_TESTER

Published:2009/7/16 3:51:00 Author:Jessie

Shows circuit using Fairchild 709 IC null amplifier in feed-back loop around linear integrated-circuit tester, and FI 0049 dual mos fet serving as chopper for displaying offset voltage and transfer function simultaneously on scope by switching in synchronism with horizontal sweep.-J. N. Giles, How to Measure Linear-IC Performance, EEE, 14:8, p 62-68 and 161.   (View)

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DEBOUNCING_TOUCH_SWITCH

Published:2009/7/13 4:47:00 Author:May

Foolproof debouncing for touch switch using toggling flip-flop (half of Motorola MC14013) is provided by two gates connected as monostable pulse stretcher. Time constant of pulse stretcher is selected to match needs of application. For status display, LED driven by 2N3903 transistor can be connected to Q terminal of flip-flop.-V. Gregory, CMOS Touch Switches-Convenient, Less $ and Sexy, EDN Magazine, May 5, 1976, p 112.   (View)

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TRANSISTOR_DIODE_AfOR_GATE

Published:2009/7/16 3:51:00 Author:Jessie

Low leakage and low storage time of silicon epitaxial transistor allow omission of base turn-off sup ply while giving medium-speed operation over wide temperature rallge, up to 2 Mc for two cascaded logic stages.-D. Hall, Using Epitaxial Transistors in Switching and R-F Circuits, Electronics, 34:13, p 52-53.   (View)

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TWO_TRANSISTOR_CASCODE_MULTIVIBRATOR

Published:2009/7/16 3:51:00 Author:Jessie

Two capacitors in voltage-divider storage circuit control transistors to give choice of rectangular or sawtooth waveforms at output of Q1, depending on time constants C1-R3 and C2-R4.-C. Sing, Advantages of Free-Running Cascode Multivibrators, Electronics, 37:5, p 28-29.   (View)

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TOUCH_SWITCH_FOR_MUSIC_KEYBOARD

Published:2009/7/13 4:46:00 Author:May

Touching metal sensor plate adds about 300pF of capacitance between plate and ground,changing RC delay network that slows down clock waveform reaehing -D input of 4013 dual D flip-flop, making flip-flop output high for duration of contact. Circuit is repeated for each key in electronic music system.-D. Lancaster, CMOS Cookbook, Howard W. Sams, Indianapolis, IN, 1977, p 278-282.   (View)

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WWV_ON_AC_DC_RADIO

Published:2009/7/16 3:50:00 Author:Jessie

When fed into IF amplifier of ordinary broadcast-band radio, simple converter circuit gives choice of WWV on 10 or 15 MHz, for reception of time signals and radio propagation reports. C2 is 1.5-10 pF; C3 and C6 are 7-60 pF; C4 is 7-100 pF (all compression trimmers); and C5 is 1.8-8.7 pF miniature variable capacitor. -W. C. Powis, Notes on Converting the AC/DC for WWV, 73Magazine, Oct. 1974, p 116.   (View)

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HIGH_NOISE_IMMUNITY_LOGIC

Published:2009/7/16 3:50:00 Author:Jessie

Basic gate uses zener with 5.5.V breakdown to give, high noise immunity for variety of logic circuits, at penalty of relatively high supply voltage. D1 prevents Q1 and Q2 from being on simultaneously, even during severe transients.-Higher-Voltage ICs Crack Noise Barrier, EEE, 14:8, p 40-42.   (View)

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AMPLITUDE_DISCRIMINATOR

Published:2009/7/16 3:50:00 Author:Jessie

High-speed trigger with adjustable bias network and cathode-follower output serves as amplitude discriminator for tachometer that responds to pulses produced by gamma radiation sources on sealed-in rotating parts not directly coupled to input or output shafts of transmissions or turbines.-R. R. Bockemuehl and P. W. Wood, Unique Two-Channel Tachometer uses Radioisotopes, Electronics, 35:49, p 44-45.   (View)

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5_MC_MVBR

Published:2009/7/16 3:50:00 Author:Jessie

Constant-current generators Q1 and Q2 conduct continuously. Timing capacitor C1 charges through Q1 and Q4 and discharges in next half-period through Q2 and Q3, all in saturated states. Output pulse amplitude is 4 V at up to 5 Mc. -V. M. Ristic, Simple Multivibrator Operates at 5 Mc , Electronics, 38:17, p 86-87.   (View)

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FREE_RUNNING_COUNTER_DISPLAY

Published:2009/7/13 4:46:00 Author:May

Atten-tion-getting circuit simply counts at predetermined rate while driving 3-digit display using 7-segment LEDs. Circuit uses two sections of 4011 CM0S quad NAND gate to generate pulses at rate controlled by 100-megohm pot. Pulses trigger 4026 counters connected as shown, with outputs a-g of each going to 7-segment LED dis-play. When all three displays reach 9, next pulse resets all to0 and count continues. Auxiliary circuit at upper right uses remaining sections of 4011 as flip-flop controlled by touch-plate switches; bridging gap between center and grounded plates with finger makes counter run. Bridging other gap resets counter to 0 and holds it there. If reset is not used, connect input pins 8, 9, 12, and 13 of unused gates to pin 14. -J. A. Sandler, 9 Easy to Build Projects under $9, Mod-em Electronics, July 1978, p 53-56.   (View)

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COMPLEMENTARY_DUAL_SCHMITT_TRIGGER

Published:2009/7/16 3:50:00 Author:Jessie

Provides inverting and noninverting outputs for pulse-width modulation.-D. D. Robinson, Linear Microcircuits Scarce? Now You Can Breadboard Your Own, Electronics,37:27, p 58-64.   (View)

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PROXIMITY_SWITCH_1

Published:2009/7/13 4:45:00 Author:May

Based on coupling of human body to 60-Hz power line. Hand held close to sensor plate induces hum into 4001B gate. This is squired and used to trip 4013 retriggerable mono MVBR. Output is clean from instant of first proximity until several milliseconds after release. Sensitivity depends on size of plate.-D. Lancaster, Clocked Logic, Kilobaud, May 1977, p 24-30.   (View)

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SINGLE_TRANSISTOR_AUTO_TACHOMETER

Published:2009/7/16 3:49:00 Author:Jessie

Uses zener diode to compensate for variations in 12-v supply. Meter is calibrated in rpm, using R3 for 0ncl adjustment. Range is 0 to 6,000 rpm. Input is ignition wave-form.-J. Cowan, Auto Tachometer Uses Transistor, Electronics, 31:33, p 92-94.   (View)

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100_Ws_PHOTOFLASH

Published:2009/7/13 4:45:00 Author:May

Uses AC supply and large storage capacitors to give intense flash lasting only about 250 ms, as required for stop-motion photography of fast-moving objects such as bullets. For battery-powered operation, T1 can be replaced by solid-state chopper circult. Contacts can be in camera or in external control device.-W. E. Hood, Lightning in a Bottle, 73 Magazine, Sept. 1974, p 109-112.   (View)

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WIDE_MARK_SPACE_RATIO

Published:2009/7/16 3:49:00 Author:Jessie

Pulse width and interpulse period are independently adjustable from tenths of microsecond to several seconds by varying Cb1-Rb1.-S. Tesic, Pulses with Variable Mark-to-Space-Ratio, Electronics, 38:14, p 78-79.   (View)

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TRICOLOR_LED_PEAK_INDICATOR_CIRCUIT

Published:2009/7/13 4:44:00 Author:May

This is a tricolor LED circuit. With a low input level, LED2 is off. As the input voltage increases, LED2 turns on and glows first green, then yellow, and finally red. Resistor R10 and 2.5-V precision voltage reference IC4 provide a precision voltage reference that is further subdivided by resistors R11, R12, R13, and R14, This chain of resistors creates three different reference voltages that set the voltage thresholds for the three LEDs, which are fed to the three comparators along with the input signal. The output of these comparators is then connected to LED2. If the output of all of the comparators is floating, the red and green dies in the tricolor LED are biased ON by R15 and R16, causing LED2 to glow yellow. However, if the output of a comparator is internally grounded, the connected color element will be pulled below 2 V, and the element will turn off. To set the gain level of the amplifier, apply a maximum-level signal to the input of the averager and reduce the level to allow for headroom.   (View)

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