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Last Updated: June 02, 2021 01:44 PM

Circuits Designed by Dave Johnson, P.E.

Alarm Sounds At Freezing TemperaturesThis electronic hobby circuit below is designed to activate a beeper alarm, whenever the outside air temperature is below 0 degrees C   (32F) .  A 9v battery powers the hobby circuit.  The average 9ua current is so low that the battery should last for many years . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006

Alternating CW & CCW Motor DriverA while back a company needed a motor controller for a custom door latching system.    The system used a small brush motor with a speed reduction gear to both latch and unlatch the door.    When pulsed for about 250ms in the clockwise direction, the motor would unlatch the door. . . Circuit by David Johnson P.E.-September, 2010

Amplifier for a Xenon Lamp Flash Detector  - This circuit has a very low standby current requirement yet has very high sensitivity toward the light flashes from a xenon lamp.  When connected to a flip/flop it can serve as an on on/off Controller. . . Circuit by David A. Johnson P.E.-February, 2002

Links to electronic circuits, electronic schematics and designs for engineers, hobbyists, students & inventors:

An Alarm Power Supply with Battery Back-up -  Power Supply Circuits:  This Power Supply is suitable for the Modular Burglar Alarm.  However, it has other applications.  It is designed to provide an output of 12-volts, with a current of up to 1-amp.  In the event of mains failure, the back-up battery takes over automatically.  When the mains is restored, the battery recharges.  __ Designed by Ron J.

An Experimental TRIAC Lamp Dimmer & Motor Speed Control using a Simulated DIA - C -  DANGERThe diac is a common component used to trigger TRIACs.  The construction of a diac is similar to that with a transistor, but with both junctions doped to similar levels so that the two junctions' revers break down characteristics are similar.  This is a fun project to demonstrate the use of a pair of bipolar transistors operating in their negative resistance region to simulate a diac triggering a TRIAC in an incandescentlamp dimmer.  The circuit is not optimized for performance -it is only intended to demonstrate the principle.   __ Designed by Dick Cappels

An improved offline driver lights an LED string -  01/25/13  EDN-Design Ideas A constant current is better than a constant voltage for driving LEDs.  In this proposed circuit, a common constant-voltage regulator is changed into a constant-current source for LEDs.  In addition, a startup current limiter is used to suppress large current surges, and a voltage chopper is employed for a wide ac input of 96 to 260 VRMS.   Design by Yan-Niu Ren, Southwest Petroleum University, Chengdu, China

An Inexpensive Tone Encoder -  Figure 1 illustrates an easy circuit that can be constructed with mostly Radio Shack parts on any general purpose circuit board.  The only rigid requirement is that capacitor C1 be stable over a wide temperature range.  Use only Mylar, Polyester or Metal film for capacitor C1. __ Designed by Radio Amateur Society of Norwich

An Infra-Red Remote Control Extender -  This is a battery powered Infra-Red Link that will allow you to change channels on your Satellite Receiver and operate the controls on your VCR & DVD from anywhere in the house.   __ Designed by Ron J

An Infra-Red Remote Control Extender -  Miscellaneous:  This is a battery powered Infra-Red Link that will allow you to change channels on your Satellite Receiver and operate the controls on your VCR & DVD from anywhere in the house.  __ Designed by Ron J.

An Intelligent 12V Fan Controller -  Does your computer make more noise than it should? It's probably mostly fan noise! Slowing the fans down will reduce the noise but if you go too far, you could end up with fricassee of CPU!__ SiliconChip

An LED Flasher with a SlowRise & Fall Time -  Here is a Simple Circuit to give a Flashing LED, With a "Rising and Falling" Brightness.  It Uses the Sawtooth waveform from pins 2 and 6 to create the rise and fall.  The Resistor and LED on Pin 3 are Optional.  The 10K Potentiometer give a reasonable range of Speed.   __ Designed by G.L. Chemelec

An On/Off Motor Control with Brake -  The circuit for the controller begins with a buffer, consisting of R1, R2, R3, and Z1A, which isolates the receiver from the rest of the circuit and makes operation of the circuit independent of the exact signal levels from the receiver.   __ Designed by Stefan Vorketter

An SCR Flipflop  for Alternating Flashing Light Bulbs -  Schematic only __ Designed by G.L. Chemelec

AN1262-Wire Virtual Remote Sensing for Voltage RegulatorsClairvoyance Marries Remote Sensing -  Linear Technology AN126 __ Designed by Jim WilliamsOct 1st, 2010

AN18Power Gain Stages for Monolithic Amplifiers -  Linear Technology AN18 __ Designed by Jim WilliamsMar 1st, 1986

AN21Composite Amplifiers -  Linear Technology AN21 __ Designed by Jim WilliamsJul 1st, 1986

AN45Measurement and Control Circuit Collection -  Linear Technology AN45 __ Designed by Jim WilliamsJun 5th, 1991

AN5Thermal Techniques in Measurement and Control Circuitry -  Linear Technology AN5 __ Designed by Jim WilliamsDec 1st, 1984

AN61Practical Circuitry for Measurement and Control Problems -  Linear Technology AN61 __ Designed by Jim WilliamsAug 1st, 1994

Analog Bar Graph Expanded Scale Voltmeter -  An expanded scale voltmeter   (ESV) can save your plane.  That may be a strong statement, but it's true.  The crucial radio link that lets you control your plane relies on nickel-cadmium   (NiCd) batteries in the transmitter and receiver __ Designed by Stefan Vorketter

Analog switch lowers relay power consumption -  20-Dec-01 EDN-Design Ideas Designers often use relays as electrically controlled switches.  Unlike transistors, their switch contacts are electrically isolated from the control input.  However, the power dissipation in a relay coil may render the device unattractive in battery-powered applications.  You can lower this dissipation by adding an analog switch that allows the relay to operate at a lower voltage  (Figure 1) Design by Steve Caldwell, Maxim Integrated Products, Chandler, AZ

Analog Voltage Controls Digital Potentiometer -  03/20/08  EDN-Design Ideas A microcontroller with an internal ADC controls a digital potentiometer via an I2C interface Design by Hrishikesh Shinde, Maxim Integrated Products, Dallas, TX

Analyzer tests reverse-recovery behavior of diodes -  07/19/07 EDN-Design Ideas Testing the reverse-recovery time of diodes yourself proves advantageous because you cannot easily compare data sheets from different manufacturers Design by Louis Vlemincq, Belgacom, Evere, Belgium

AND Gate Lets Sleeping Controllers Lie -  05/23/96 EDN-Design Ideas Battery-operated portable equipment often makes use of  80L51 P's power-down mode to conserve battery energy.  CMOS -memory contents are critical in many of se systems, so  system must sustain  CMOS -memory-supply voltage without interruption and for as long as possible.     In Figure 1, a P supervisor  (IC1]guards  P  (IC3]against Design by Dana Davis, Maxim Integrated Products, Sunnyvale, CA

Another Simple Circuit FM Transmitter -  Here is the schematic, PC board pattern, and parts placement for a low powered FM transmitter.  The range of the transmitter when running at 9V is about 300 feet.  Running it from 12V increases the range to about 400 feet.  This
transmitter should not be used as a room or telephone bug.   __ Designed by Kamran Ahmed-UK

Anti-Flicker for LED Christmas Lights -  I like the idea of LED light strings that rarely need new bulbs but the flicker drives me crazy! Here's the solution for single strings of LEDs all in series __ Contact: Charles Wenzel of Wenzel Associates, Inc.

APD-bias has adjustable output -  05/22/97 EDN-Design Ideas The avalanche-photodiode detector  (APD], like the PIN diode, serves as a receiver in optical communications systems.  The APD is more sensitive, but you must properly bias it to produce the appropriate electron flow for a given flux of photons.  An external D/A converter allows dynamic,.    Design by Larry Suppan, Maxim Integrated Products, Sunnyvale, CA

Appliance Timer-Cum-Clap Switch -  PANKAJ D.  CHOUDHURY When planning for a week-end outing to return late in the evening, we are often in an ambivalence whether to leave the staircase/outside light on or off. We sometimes...__ Electronics Projects for You

Arduino Solar Charge Controller -  8-Aug-14 -Design News:   Solar power has the advantages of being low-maintenance and pollution-free, but the main drawbacks are high fabrication costs and low energy conversion efficiency.  Since solar panels still have relatively low conversion efficiency, the overall system costs can be reduced using an efficient solar __ Gadget Freak-Case #260

Astable Multivibrator Lights LED From a Single Cell -  08/21/08 EDN-Design Ideas A classical multivibrator drives a step-up inductor to power an LED from a single cell Design by Luca Bruno, ITIS Hensemberger, Monza, Lissone, Italy

AT89c2051 Night Light Saver -  Build a device that turn on and off a night light automatically.  Save Energy, No EMI, No Battery, Built-in Lamp Fixture, and Peak Shaving.   __ Designed by Wichit Sirichote

AT89c2051/4051 Stepper Motor Interface -  M1 is a stepper taken from an old disk drive.  There are five pins, i.  e.  , common, coil 1, 2, 3 and 4.  Resistance measured between common pin and each coil is about 75 Ohms.  Driving current for each coil is then needed about 60mA at +5V supply.  A darlington transistor array, ULN2003 is used to increase driving capacity of the 2051 chip __ Designed by Wichit Sirichote

Attention-Grabbing 'Blue Light Special' -  16-Mar-09 -Design News:   William Grill wanted to draw attention to a trade show booth.  He considered a big neon sign, loud music and a provocative attitude, but instead he created this attention-getting gadgethis "Blue Light Special." Grill made this gadget with a mere $15 in materials.  It is built around Microchip __ Gadget Freak-Case #137

Attenuator provides optical-power control -  EDN-Design Ideas 10/17/06    Based on nanoparticle technology, these dynamic attenuators feature optical-power-control technology in an LC-plug style attenuator housing.The device controls optical power by limiting or clamping optical power at preset values, reducing optical-power spikes and improperly set power levels from damaging sensitive receivers and equipment.    Design by Molex, www/molex/com

Attenuators Nullify Temperature Deviations -  08/17/98 EDN-Design Ideas NOTE :  File has several circuits, scroll to this one.  You can use the circuits in Figure 1 to temperature-compensate a dc voltage of any circuit if the voltage-versus-temperature curve meets the following criteria:   The curve is stable in time at the same temperature;  The curve is reproducible under repeated temperature cycling;  The curve is monotonic within the necessary after-compensation accuracy   (in other words, the curve doesn't have local fluctuations that exceed the maximum-allowable after-compensation flatness);
The curve has either a positive or negative slope or is C-shaped. Design by Semyon Lapushin, Electronic System Products, A Division of Antec, Norcross, GA

ATV Repeater Controllers -  Specifications and designs are subject to change without notice.
Use on your own risk. __ Designed by Mijo Kovacevic, S51KQ

Audio Activated Recorder -  ScanMate connects between your scanner and tape recorders (via the recorder's microphone or auxiliary input and its remote start jack). __ Designed by Tony van Roon  VA3AVR

Audio Activated Switch -  This circuit will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.    It could be used to turn on a relay, routing the signal to were it is needed.. . . Circuit by Dave Johnson P.E.-July, 2006

Audio Amp makes efficient fan controller -  11/09/00 EDN-Design Ideas You can use discrete transistors to vary power to a fan to control its speed.  However, with a simple modification, you can use an audio-amplifier IC to control a fan module  (Figure 1).  The LM4872.   PDF contains multiple circuits, scroll to find the one of interest Design by Wallace Ly, National Semiconductor Corp, Santa Clara, CA

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