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Last Updated: January 01, 2018 04:02 AM
Circuits Designed by Dave Johnson, P.E. :
Universal DC Sink to Source Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are other  systems which require a common ground connection instead of a common V+ supply . . . Hobby Circuit designed by David Johnson P.E.-March, 2011

Water Seepage Monitor -  A while back I received a request from a company who needed a water seepage detector.  They wanted a device that ran on 24vac and detected water using a fully isolated circuit.  They wanted a circuit which switched off 24vac to a load when water was detected . . . Circuit by Dave Johnson P.E.-January, 2011

Capacitance Proximity Switch
Draws very low power - Ideal for battery-powered applications
6 Models Available - Call 806-368-7747




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

UHF Remote Mains Switch Transmitter -  Designed to control the UHF Remote Mains Switch, this hand-held transmitter can operate over a 200m range.  it's based on a PIC  micro and a pre-assembled transmitter module, making it easy to build and get going.__ SiliconChip

ultra high isolation SPDT switch -  Application Note__ MiniCircuits.com

Ultra Low Voltage N-Channel Analog Switch Transmission Gate -  Circuit ideas for Designers App Note__ Advanced Linear Devices, Inc

UltraLow Power Standalone Motion Switch  -  Equipment Needed The following equipment is needed: , Bullet text, Getting Started Load the evaluation software by placing the CN0274 Evaluation Software CD into the PC.  Using My Computer, locate the drive that contains the evaluation software CD and open the Readme file.  Follow the instructions contained in the Readme file for installing and using the evaluation software.  CiRCUiT EVALUATiON AND TEST, Setup Connect the 120-pin connector on the CN0274 Evaluation Software to the connector on the EVAL-SDP-CS1Z__ Analog Devices from the Lab

Ultra-Sensitive Solid State Clap Switch -  Here is the circuit of a highly sensitive clap switch that can be operated from a distance of up to 10 metres from the microphone.  Signals picked up by the microphone are amplified by transistors T1, T2, and T3.  Diode D1 detects clap signals and the resulting positive voltage is applied to the base of__ 

Ultrasonic Dog Whistle -  it's well known that many animals are particularly sensitive to high-frequency sounds that humans can't hear.  Many commercial pest repellers based on this principle are available, most of them operating in the range of 30 to 50 kHz.   __ Designed by Tomaz Lazar-Ljubljana, Slovenia

Ultrasonic switch transmitter & receiver -  The circuit described generates (transmits) ultrasonic sound of frequency between 40 and 50 kHz.  As with any other remote control system this cirucit comprises of a minI transmitter and a receiver circuit.  Transmitter generates ultrasonic sound and the receiver senses ultrasonic sound from the transmitter and switches on a relay __ Designed by Andy Wilson

Universal 4 Digit Keypad Operated Switch -  This is a universal version of the Four-Digit Alarm Keypad.  I'vemodified the design of the output section - to free up the relay contacts.  This allows the circuit to operate as a general-purpose switch.  I used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application.   __ Designed by Ron J

Universal DC Sink to Source Converter -  As illustrated below, many control systems use an open collector transistor to turn something on.  Perhaps it is a LED light, a relay or a small motor.  However there are other  systems which require a common ground connection instead of a common V+ supply . . . Hobby Circuit designed by David Johnson P.E.-March, 2011

USB Printer Sharing Switch -  I had two computers, a Mac MinI and a generic Windows computer.  Both were on different networks, but in the same room, and I wanted to share a Lexmark USB laser printer between the two of them.  I ended up making this switch to share the printer between the two computers __ Designed by Dick Cappels

USB switch -  You can connect one USB device like a printer or scanner on 2 computers and controlled by software __ Designed by © Vassilis Serasidis

Using Model PSW-1201 as a SPST switch -  AN-80-001 Application Note__ MiniCircuits.com

Using the RSW-2-25P switch -  AN-80-004 Application Note__ MiniCircuits.com

VersaTimer/Switch with Self-Latching Relay -  Use it as a micropower switch, programmable timer and/or 12V battery protector__ SiliconChip

VGA Switch -  Digital VGA switch for switching between two PC monitors with MAX465 IC __ 

Voice activated switch -  The VS-1 provides quality components and a compact printed circuit board that makes it a snap to turn on a multitude of devices, from HAM transmitters and amps to tape recorders or clandestine listening equipmentHAVE FUN! __ 

Voice activated switch  -  This circuit uses an MC2830 to form a voice activated switch (VOX).  A traditional VOX circuit is unable to distinguish between voice and noise in the incoming signal.  in a noisy environment, the switch is often triggered by noise, or the activation sensitivity must be turned down.  This circuit overcomes this weakness.  The switch is activated by voice level above the noise and not activated by background noise. __ Contact IQ Technologies

Voice identifier for a repeater station -  Designed as a drop-in replacement for the VHF Engineering repeater's CWiD, it can be used in other equipment too. __ Designed by Manfred Mornhinweg

Voice Operated Switch -  Description This circuit is a voice operated switch (VOX) and designed for audio frequencies within a commercial telephone bandwidth of 100Hz to 3000Hz.  input amplitude is sensitive down to 10mV and the output comparator can drive a relay or interface to micro processors and TTL switching between 0 and 5Vdc.  Notes The VOX circuit is […]__ 

Voice Recorder & Playback System -  There are several types of voice recorder and playback systems available in the market but most of them are expensive and their circuits are also very complex to assemble.  Here is__ Electronics Projects for You

Voice-Over -  This is a circuit where a microphone and preamp circuit (voice circuit) have priority over any other audio signal.  You can think of this as a one way intercom, if the main amplifier is used for listening to music, then when the push to talk switch is pressed, the amplifier is switched to the voice signal.   __ Designed by Andy Collison

Voltage Comparator Switch -  This circuit will provide an indication whenever the input voltage differs from two defined limits, V1 and V2.  The supply voltage, Vcc must be higher than the highest input voltage by at least 2 volts.  One application here is to monitor a 12V car battery __ Designed by Andy Collison

Voltage Controlled Switch using 555 -  in this circuit the 555 timer is used in a novel way, as a voltage controlled switch.   __ Designed by Miroslav Adzic

Voltage-Based Controller for Switches -  Here’s a simple circuit for controlling four switches from a distance through just a pair of wires.in the circuit, the inverting inputs (pin 2) of operational amplifiers IC 1 through IC 4 are__ Electronics Projects for You

Vxi Switching Application Note 5968-7234 -  Application Note__ Aligent

Water & vandal-proof keypad uses piezoelectric disc as sensor & buzzer -  04/21/14  EDN Design Ideas:  An ingenious and low-cost method to create a rugged “Ui”.  This design was done to get a sealed keypad for very wet environments (in my particular case, showers for swimming pools).  The keypad needed to be able to detect slight pressure on a stainless steel plate 0.4mm thick.  Apart from water protection, the solution offers an esthetical finish, as the user side is absolutely flat, with nothing visible other than the silkscreened print.  Another advantage of this type of keypad is that it is vandal-proof __ Circuit Design by Francesc Casanellas

Water Activated Relay -  in his circuit Marin has used two transistors wired as a high gain compound pair.  Transistor T1 may be a 2N2222A and T2 a BC108.  The current gain will be the product of each transistors beta, which will be a minimum of 140 x 110 or 15400.  The power supply used can be any voltage from 4.5 to 15 volts,  __ Designed by Marin Lukas

Water Seepage Monitor -  A while back I received a request from a company who needed a water seepage detector.  They wanted a device that ran on 24vac and detected water using a fully isolated circuit.  They wanted a circuit which switched off 24vac to a load when water was detected . . . Circuit by Dave Johnson P.E.-January, 2011

Waterproof Bathroom Switch -  The object of this circuit is turn the domestic lighting on and off in complete safety in a room with very high humidity.  A detector, flush-mounted into the wall, detects the magnetic field variations.  must register on this site __ Designed by Published in Elecktor July/Aug, 2010

Wave Multiplier for music Synthesizers -  The idea for this project came from the fabled middle section of the Serge wave multipliers.  At the time I designed this, I had never seen or heard one of these units, nor had I seen its schematic diagrams, but armed with descriptions and suppositions by various people who had seen them, and a couple of photos of CRO traces from the output of the module, I decided to design myself one. __ Designed by Ken Stone

Whistle Activated Switch Using Um3763 -  Surprisingly much, can turn on – shut down electric devices with a whistle sound.  This is simple sound control circuits, that different from a little common circuit is Requires high frequency noise Such as whistle sound etc.  The heart of working in this circuit is IC 1 (UM3763) that is designed for this particular work.  Figure__ 

Whistle On-Whistle Off -  This CMOS toggle flip flop circuit has an addition of2bandpass filters and condenser microphone so the relay can be toggled by whistling at it.   __ Designed by Bill Bowden

Whistle Responder -  Beeps when hears your whistle; A gadget suitable for key-holders, games etc __ Contact Flavio Dellepiane, fladello @ tin.it

Whistle Switch -  The whistle switch allows you to turn on, or off, an appliance by whistling at it.  I originally built the whistle switch in 1974.  Do not attempt to duplicate it from the schematic below, but instead, understand the functions and duplicate these functions with more modern components.   __ Designed by Michael Ellis

Whistler: Electronic Trainer/Coach -  This device makes it possible to generate beeps at chosen regular time intervals for timing track race training.  Each time interval is indicated by a beep, and the end of a performance test is indicated by a double beep.  Two types of test are allowedmust register on this site __ Designed by Published in Elecktor July/Aug, 2010

White LED driver backlights LCD & keypad -  13-Nov-03 EDN Design Ideas:  Designers widely use white LEDs to backlight color LCDs and keypads in handheld devices, such as cell phones, MP3 players, GPS navigators, and PDAs.  Their spectrum and brightness represent near-ideal light sources.  One possible configuration for a phone or a phone/PDA combination is to have a group of three LEDs to light the display and six LEDs for the keypad __ Circuit Design by Fabien Franc, Catalyst Semiconductor, Sunnyvale, CA

XY Keypad uses µC's Serial Port -  10/10/96 EDN Design Ideas:  interfacing an X-Y keypad to a microcontroller usually uses a parallel port of 8 bits or more.  But with the circuit shown in Figure 1, a more efficient interface using a microcontroller's serial port reduces the number of connections required from eight to three.  This interface uses the MM74C922N, a National Semiconductor keypad encoder,  __ Circuit Design by James Mears, National Semiconductor, Tacoma, WA

Zener level-shifter drives high-side switch -  06/16/2014  EDN Design Ideas:  Simplify a high-side driver by replacing a transistor with a Zener diode.  Microcontrollers, the heart of all modern electronic gadgets, are increasingly powered with sub-5V power supplies.  This complicates the control of external loads powered by higher voltages.   __ Circuit Design by Dhananjay Gadre & Nidhi Sharma

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.

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