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Last Updated: June 02, 2021 01:44 PM

Circuits Designed by Dave Johnson, P.E.

Touch Activated SwitchThis circuit provides about one watt of non-isolated DC power for an automotive type 12v LED array lamp in addition to a standard incandescent table lamp.. . . Circuit by David A. Johnson P.E.-January, 2002

Transistor-Switch Detects Audio SignalFor some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Transmitter for Line Powered Xenon FlashThis line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000




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

Time Delay Relay -  A time delay relay is a relay that stays on for a certain amount of time once activated.  This time delay relay is made up of a simple adjustable timer circuit which controls the actual relay.  The time is adjustable from 0 to about 20 seconds with the parts specified.  The current capacity of the circuit is only limited by what kind of relay you decide to use __ Designed by Aaron Cake

Time Delay Relay II -  When activated by pressing a button, this time delay relay will activate a load after a specified amount of time.  This time is adjustable to whatever you want simply by changing the value of a resistor and/or capacitor.   __ Designed by Aaron Cake

Time Delay Relay-Power OFF -  The two circuits below illustrate opening a relay contact a short time after the ignition or ligh switch is turned off.  The capacitor is charged and the relay is closed when the voltage at the diode anode rises to +12 volts. __ Designed by Bill Bowden

Time Delay Relay-Power ON -  Here's a power-on time delay relay circuit that takes advantage of the emitter/base breakdown voltage of an ordinary bi-polar transistor.  The reverse connected emitter/base junction of a 2N3904 transistor is used as an 8 volt zener diode which creates a higher turn-on voltage for the Darlington connected transistor pair.  Most any bi-polar transistor may be used, but the zener voltage will vary from about 6 to 9 volts depending on the particular transistor used.  Time delay is roughly 7 seconds using a 47K resistor and 100uF capacitor and can be reduced by reducing the R or C values. __ Designed by Bill Bowden

Time-Controlled Switch using PIC16f72 -  APRIL 2012: A time-controlled switch is an automatic timer switch that turns an appliance ‘on’ for the desired time duration.  After the preset time duration, the timer automatically switches off, disconnecting...__ Electronics Projects for You

Time-delay relay uses proximity control -  03/15/01 EDN-Design Ideas You can build a circuit that allows a passerby to briefly operate model trains in a display window(Figure 1).  The design uses a proximity detector rather than a pushbutton switch to eliminate the need to mount and wire any equipment outdoors.  The circuit worked well Design by Dennis Eichenberg, Parma Heights, OH

Timer automatically shuts off -  08/17/00 EDN-Design Ideas The circuit in Figure 1 is a programmable power switch that offers on-state periods of 5 sec to three hours.  It consumes zero power in the off state and has zero voltage drop in the on state.  S1 is a power-on switch.  When you press S1, the battery powers an eight-pin PIC12C508 µC Design by Yongping Xia, Teldata Inc, Los Angeles, CA   

Timer Controls DSP-Filter Frequency Resolution -  04/13/95 EDN-Design Ideas To implement low-frequency digital filters, you can use low-power microcontrollers instead of dedicated DSP ICs.  However, using 8-bit or even 16-bit math can quickly lead to significant filter dynamic-range errors and to complicated routines for precise digital-filter coefficients.  By using a µC's 8-bit timer to set the sampling rate for a digital filter's data processing, you can obtain finer frequency resolution while using simple math routines. Design by D Hayden, Tempo Research, Vista, CA

Tiny 2313 Project Development Board -  This is my first time using the AVR.  I like to learn using the ATTiny 2313, because it is faster than MCS-51, cheap and the circuit is very simple.  The chip has only 20 pins.  I was interested because I want to build a simple line follower robot controlled by this MCU.   __ Designed by Tahan Prahara

Tiny Robot -  Recently many kind of robot contests have being opened and some interesting reports of the challenge are found on the web.  The Line Following is a kind of the robot contests to vie running speed on the line.  I build a tiny line following robot which can run on the desk, moving the key board aside will do.  It is for only a personal toy reduced i  __ Designed by The Electronic Lives Manufacturing-presented Chan

TinyIR Learning IR Remote Control Receiver -  Adding IR remote control to your next project, or to an existing one just got a whole lot easier.  With TinyIR, just apply power, train the chip to recognize the key codes you want to use, and you're ready to go.  Code patterns are safely stored in internal non-volatile EEPROM.  The chip can be re-trained many times if needed

Tone Control -  This is mono tone control which contain 2 potensiometers to control the level of bass tone and treble tone.  You could make the stereo tone control by duplicate this circuit, use stereo potensiometers and add mono potensiometer at input or output for balance adjustment.

Tone Control -  Based on the classic Baxendall tone control circuit, this provides a maximum cut and boost of around 10dB at 10K and 50Hz.  As the controls are passive, the last transistor provides a slight boost.  The output.   __ Designed by Andy Collison

Tone Control using TDA1524A Tone Control IC -  This simple tone control can be used in may audio applications.  It can be added to amplifers, used as a stand alone control module, or even built into new and exciting instruments.  It's one IC construction makes it a very compact circuit, as only a few support components are required.  Plus, it does not use a dual power supply.  This means that the circuit will run from 9V to 15V (although the bass will be a little weak at 9V).  The circuit is by Robert Barg and originally appeared in the Think Tank column of the May 1998 issue of Popular Electronics.   __ Designed by Aaron Cake

Tone Detector -  This is also designed to be in conjunction with the sound detector amp/electret mike amp.  this circuit is designed to trigger on a 1 khz tone.  to change this frequencyrefer to the table below, then change the resistor and capacitor values accordingly __ Designed by Andy Wilson

Tone Generator -  this tone generator can be used to control your robot.  you will need to use the tone decoder for this.  to widen the range, higher or lowersubstitute a higher, or lower valued capacitor for c1.   __ Designed by Andy Wilson

Top RC-Gun -  This is our original R/C aerial combat system. Simple one-IC construction. Please note that it has been replaced by the Top RC-Gun AWS project (see link above). __ Designed by T. Black

Top RC-Gun AWS -  This fun R/C aerial combat system lets you command your own dog fight missions. It is based on the HobbyZone Combat module. __ Designed by T. Black

Touch Activated Switch -  This circuit provides about one watt of non-isolated DC power for an automotive type 12v LED array lamp in addition to a standard incandescent table lamp.. . . Circuit by David A. Johnson P.E.-January, 2002

Touch and/or Remote Controlled Light Dimmer -  Old-fashioned light dimmers with knobs are passe! This one dims up or down at a touch or you can use an infared remote control.__ SiliconChip

Touch and/or Remote Controlled Light Dimmer-Part 2 -  Completing the construction and building the touchplate and pushbutton dimmer extensions.__ SiliconChip

Touch Dimmer -  By simply touching this touch dimmer you can increase the light intensity of incandescent lamps in three steps.  The touch dimmer is built around 8-pin CMOS IC TT8486A/TT6061A specifically manufactured for...__ Electronics Projects for You

Touch Sensative Relay Switch -  Our TOUCHER-TRS1 has many applications; Turn on for predetermine time light motor etc simply by touching sensitive metal pad.  Use the kit anywhere you’d like to draw an audience and a smile show friend your magic-touch.  The unique small design will allow you to mount kit almost anywhere.  Operates from 9 to 12VDC (optional), or via one of our 9 or 12 battery simulator/regulator kits.  The alternative uses are endless.  It’s designed for the beginner as well as the expert.   __ Contact: Kit from Elich Industrial Development, Corp

Touch Switch using 4011 CMOS NAND Gate IC -  A touch switch is a switch that is turned on and off by touching a wire contact, instead of flicking a lever like a regular switch.  Touch switches have no mechanical parts to wear out, so they last a lot longer than regular switches.  Touch switches can be used in places where regular switches would not last, such as wet or very dusty areas __ Designed by Aaron Cake

Touch-Activated Timer Switch Extends Battery Life -  10-Jul-08 EDN-Design Ideas Designed to fit into the battery compartment of an optical mouse, this circuit automatically shuts off the battery after a time delay Design by Israel Schleicher, Prescott Valley, AZ

Touch-controlled Dimmer -  Here’s a dimmer that, besides being touch-controlled, also has a setting memory that enables it, for example, to turn the lighting on at the level you had set last time it was turned off.  The project uses a specialized IC, an LS7534 from LSI Computer Systems, available from Farnell, among othersmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

Trace dimension control reduces crosstalk -  02/17/97 EDN-Design Ideas If you assemble a high-performance system using multiple single-board computers and a common backplane, you can encounter unacceptable levels of coupled noise, or crosstalk.  This problem can plague such high-speed systems as real-time image-recognition systems or real-time video servers.  Crosstalk, which is unwanted voltage capacitively coupled from a switching line to an adjacent quiet line, can cause false switching and random failures that are difficult and time-consuming to troubleshoot.   Design by Raymond Cosimano, Cosco Technologies, Endicott, NY

Track Controller forAwana®Grand Prix -  Schematic Only   (also pinewood derby) measures and displays finish times, sends results to computer. Works with "grandprix race manager" from grandprix software central. (16f628)  __ Designed by Jon Fick

Traffic Light -  A two-way traffic light using a CMOS 4017 and 555.  To be used as toy only __ Designed by Jose Pino

Traffic Light 2 -  A two-way Traffic light using a PIC 12F629. As bonus, a traffic light that doesn't use a PIC is included. (05/13/2004) __ Designed by Jose Pino

Traffic Light Controller -  Controls on3 LED traffic light sequence __ Designed by rstevew@armory.com

Transistor Flasher  -  The basic two-transistor flasher shown below has found its way into dozens of applications due to its simplicity and versatility.  Applications have included such diverse circuits as a micropower low battery indicator, a lightning detector, .   __ Contact: Charles Wenzel of Wenzel Associates, Inc.

Transistor junction monitors remote temperature -  06/22/00 EDN-Design Ideas The circuit in Figure 1 uses a regular, general-purpose transistor as the sensing element and a thermal-diode monitor IC to measure temperature.  The ADM1021 usually connects to an on-chip thermal diode on a CPU die itself, but in this application the sensor connects to a regulator low-cost discrete npn transistor, the 2N3904 Design by Matt Smith, Analog Devices, Limerick, Ireland

Transistor junctions monitor temperature zones -  12/31/69 EDN-Design Ideas  A simple circuit uses transistor junctions to monitor multiple temperature zones.  The temperature sensors are ordinary, general-purpose, low-cost, diode-connected transistors.  The well-known diode equation VBE =(kT/q)'ln(IC /IS) shows that there is a temperature dependency of approximately 2.2 mV/°C for a base-emitter junction.   Design by Matt Smith, Analog Devices, Limerick, Ireland

Transistor LED Flasher -  A simple LED flasher that uses only two transistors, one capacitor and one resistor.  This basic oscillator can have other simple applications.   __ Designed by Jose Pino

Transistor LED flasher -  This circuit has a lot going for it.  For one thing, it only consists of two transistors, two capacitors and four resistors.  That also means it consumes very little power.  You can control the flash rate by changing the size of the 100k resistors   (100k makes for a pretty slow rate).  You can also control the duty cycle by using resistors of different values on the two sides __ Designed by Colin Pringle

Transistor Organ -  This simple circuit can provide hours of enjoyment as you learn tunes, play duets or just make some really weird sounds by pushing all the buttons at once.  You have probably seen this circuit before, it is fairly common.  I have seen it in several __ Designed by Aaron Cake

Transistor quickly wakes sleeping LDO -  09/01/98 EDN-Design Ideas NOTE :  File has many circuits, scroll down.  Portable systems, such as telephone handsets, make extensive use of low-dropout (LDO) regulators.  These components provide noise-sensitive parts with a stable power-supply line.  When a telephone enters standby mode, most of the circuits go to sleep by disabling the LDO's outputs.  Operating current thus drops to a minimal level.  When a user starts to dial a number, the LDO receives an enable signal and immediately delivers the nominal operating voltage.  Unfortunately, most low-noise LDOs use a bypass capacitor that briefly loads the internal reference voltage upon wake-up. Design by Christophe Basso, Motorola Semiconductor, Toulouse, France

Transistor-Switch Detects Audio Signal -  For some audio systems it is desirable to have an automatic switch circuit turn on other devices, such as an amplifier, if an audio signal is detected on one line.  The hobby circuit below will activate a transistor switch when it detects at least 50mv peak to peak of an audio signal.  The switch could be used to turn on a relay, routing the signal to where it is needed.  A single 3v lithium cell will power the electronic circuit for about 5 years . . . Hobby Circuit designed by David A. Johnson P.E.-July, 2006

Transmitter for Line Powered Xenon Flash -  This line powered xenon flash circuit drives a small camera type flash tube.  It has an optical isolator to allow the flash to be safely triggered from some remote device.  A flash rate of 2Hz is possible with the circuit . . . Hobby Circuit designed by Dave Johnson P.E.-June, 2000

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