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Last Updated: January 01, 2018 04:02 AM
Circuits Designed by Dave Johnson, P.E. :
Piezoelectric Tap Switch -  This circuit uses a flat piezo wafer, glued inside a plastic box, as a finger tap sensor.  With each tap of a finger to the box holding the wafer, the circuit turns on and off AC or DC power to an external device.  The circuit is powered by a 9v battery . . . Circuit by David A. Johnson P.E.-December, 2010

Piezoelectric Triggered Switch -  Two different switch circuits are shown.  One sources current and the second sinks current.  Both switches are connected to a piezo wafer.  When the wafer is tapped, the switches are activated . . . Circuit by David A. Johnson P.E.-February, 2002

Piezoelectric Vibration Sensor Activates Switch -  An inexpensive piezo device is used as a motion sensing device for this motion alarm . . . Circuit by David Johnson P.E.-July, 2006

Pop Free Microphone On/Off Switch Circuit -  This circuit uses a simple technique to eliminate the usual “pop” sound when an electret type microphone is switched on or off.  The circuit is completely passive and will work on dynamic and electret type microphones . . . Circuit by David Johnson P.E.-February, 2002

Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Pushbutton Activates Service Request Beeper -  A single press of a pushbutton switch turns on a beeper for one second but can’t be activated again for 60 seconds.   . . . Circuit by David Johnson P.E.-September, 2005

Pushbutton Oneshot & Latch -  This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal.  it can operate from 3v to 18v . . . Circuit by David A. Johnson P.E.-March, 2002

Pushbutton On-Off Latch Circuit -  Often you want to turn on and off power to a device with a single pushbutton switch.  The circuit below performs this logic function with just a few parts and can operate from DC supplies between +3v to about 15v.  it uses two inverters within a 74C14 or a CD4069 hex inverter package.  Each press of the button toggles between the two on/off logic states.   . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2010

Pushbutton Switch Through Glass  -  This simple technique allows a mechanical pushbutton switch assembly to activate a reed type relay through a pane of thick glass.  Pushing the button moves a magnet near the reed relay, closing the relay contacts . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Pushbutton Switch works through Glass -  This simple technique allows a mechanical pushbutton switch assembly to activate a reed type relay through a pane of thick glass.    Pushing the button moves a magnet near the reed relay, closing the relay contacts.   . . . Circuit by Dave Johnson P.E.-February, 2002

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:

PC parallel port eight DC power switch cam driver two unipolar stepper Motors, lights etc -  On this circuit there are eight DC power switch you can open or close through PC parallel port: you can use it to drive two unipolar stepper motor or eight electric light bulb or DC motors.  Digital interface to PC uses optocouplers for safety reasons and you can connect up to six circuits to a single LPT, driving up to twelve step motors or 48 bulb: see iso-buffer for an in deep description. __ Designed by © Vincenzo Villa

PC Power Switch -  Simplest ever PC switching unit, turn on peripherals with the PC __ Designed by Rod Elliott  ESP

PCB layout considerations for non-Isolated switching power supplies -  07/20/12  EDN Design Ideas:  The best news when you power up a prototype supply board for the very first time is when it not only works, but also runs quiet and cool.  Unfortunately, this does not always happen.  A common problem of switching power supplies is "unstable" switching wav __ Circuit Design by Henry J. Zhang, Applications Engineering Manager, Power Products, Linear Technology Corp.

PCMCIA Socket Voltage Switching Design Note 93 -  DN93 Design Notes__ Linear Technology/Analog Devices

Perimeter Monitor -  Using a single cable such as speaker wire or doorbell cable, this circuit can be remotely positioned, for example, at the bottom of a garden or garage, and used to detect all sound in that area.  The cable can be buried in a hosepipe or duct and is concealed out of sight.  The mic is an ordinary dynamic mic insert __ Designed by Andy Collison

Petrol Gas Switch For A Pajero -  My current vehicle, a Pajero, was modified for dual fuel – ie, petrol and gas.  However, it’s necessary to run the vehicle on petrol at regular intervals to stop the injectors from clogging up.  This simple circuit allows the vehicle to be started using petrol and then automatically switches it to gas when the speed__ 

Piezoelectric Tap Switch -  This circuit uses a flat piezo wafer, glued inside a plastic box, as a finger tap sensor.  With each tap of a finger to the box holding the wafer, the circuit turns on and off AC or DC power to an external device.  The circuit is powered by a 9v battery . . . Circuit by David A. Johnson P.E.-December, 2010

Piezoelectric Triggered Switch -  Two different switch circuits are shown.  One sources current and the second sinks current.  Both switches are connected to a piezo wafer.  When the wafer is tapped, the switches are activated . . . Circuit by David A. Johnson P.E.-February, 2002

Piezoelectric Vibration Sensor Activates Switch -  An inexpensive piezo device is used as a motion sensing device for this motion alarm . . . Circuit by David Johnson P.E.-July, 2006

Polarity Reversal Switch -  Switch the absolute polarity (180° phase shift) of signals with this simple circuit __ Designed by Rod Elliott  ESP

Pop Free Microphone On/Off Switch Circuit -  This circuit uses a simple technique to eliminate the usual “pop” sound when an electret type microphone is switched on or off.  The circuit is completely passive and will work on dynamic and electret type microphones . . . Circuit by David Johnson P.E.-February, 2002

Power Load Sensing Automatic Switch -  WARNiNG:  This circuit requires experience with mains wiring.  Do not attempt construction unless experienced and capable.  Death or serious injury may result from incorrect wiring.   __ Designed by Rod Elliott  ESP

Power switch provides soft start -  03/30/00 EDN Design Ideas:  in the circuit in Figure 1, series-connected MOSFETs turn on the line voltage near the zero-crossing point and off when the 555-timer delay lapses.  That delay ranges from 1 to 7 msec.  The MOSFETs’ body diodes and the 1N4005 diodes form a full-wave bridge rectifier __ Circuit Design by John Haase, Colorado State University, Fort Collins, CO

Printer port activates CMOS switches -  05/02/02 EDN Design Ideas:  The cost-effective design in Figure 1 provide as control for CMOS switches without the need for an external power supply.  Analog switches such as those in the MAX4663 are ideal for use in low-distortion applications.  They are preferable to electromechanical relays in automatic test equipment or other applications in which you need current switching __ Circuit Design by J Jayapandian, IGCAR, Tamil Nadu, India

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

Programmable 3 phase Controller for ON/OFF Motor -  Automatic on/off controller for a 3-phase electric motor can be made with a programmable time switch.  in this case a maximum of eight time durations can be programmed.  The system has two__ Electronics Projects for You

Protects from Battery Polarity Reversal -  This simple circuit can protect a sensitive electronic circuit from an accidental connection of a battery with a reversed polarity.  The N-channel FET connects the electronic device to the battery only when the polarity is correct.  The circuit shown was . . . Hobby Circuit designed by Dave Johnson P.E.-March, 2002

Proximity Switch -  This circuit is for an unusually sensitive and stable proximity alarm which may be built at very low cost.  if the negative terminal is grounded, it will detect the presence of a hand at more than 200mm.  if it is not grounded, this range is reduced to about one-third.  The Proximity Switch emits a loud, __ 

Push Button Motor Control -  This circuit uses solid state switching (transistors) to control direction of a DC motor.  You have precise control of the movement of the motor, and an indication of direction provided by LED's.   __ Designed by Andy Collison

Push Button Switch Debouncer -  This circuit will remove the transient spikes and contact bounces from a non-latching push button switch.   __ Designed by Andy Collison

Push Off Push On -  The ubiquitous 555 has yet another airing with this bistable using a simple push-button to provide a push-on, push-off action.  it uses the same principle of the stored charge in a capacitor taking a Schmitt trigger through its dead-band.  Whereas the Schmitt trigger in that reference was made from discrete components, the in-built dead-band arising__ 

Pushbutton Activates Service Request Beeper -  A single press of a pushbutton switch turns on a beeper for one second but can’t be activated again for 60 seconds.   . . . Circuit by David Johnson P.E.-September, 2005

Pushbutton Control for Single-Phase Appliances -  This circuit lets you switch off and switch on a single-phase appliance using two separate push switches.  Such an arrangement is common for industrial motors (mostly 3-phase) where an isolation is__ Electronics Projects for You

Pushbutton Oneshot & Latch -  This circuit uses a single IC to convert a noisy pushbutton switch signal into a clean pulse or a sustained push on-push off signal.  it can operate from 3v to 18v . . . Circuit by David A. Johnson P.E.-March, 2002

Pushbutton On-Off Latch Circuit -  Often you want to turn on and off power to a device with a single pushbutton switch.  The circuit below performs this logic function with just a few parts and can operate from DC supplies between +3v to about 15v.  it uses two inverters within a 74C14 or a CD4069 hex inverter package.  Each press of the button toggles between the two on/off logic states.   . . . Hobby Circuit designed by Dave Johnson P.E.-January, 2010

Pushbutton Relay Selector -  This circuit was designed for use in a hifI showroom, where a choice of speakers could be connected to a stereo amplifier for comparative purposes.  it could be used for other similar applications where just one of an array of devices needs to be selected at any one time.  A bank of mechanically interlocked DPDT__ 

Pushbutton replaces rotary switch -  26-Oct-00 EDN Design Ideas:  The problem of setting any one of four modes of aµC-operated process has a straightforward solution  Have the µC check the states of some 4 bits of aµC.    __ Circuit Design by Abel Raynus, Armatron International Inc, Melrose, MA

Pushbutton switch controls power supply & µC -  09/25/97 EDN Design Ideas:   Switching handheld units on and off with a pushbutton switch is a desirable feature.  Thus, switching-regulator/ controller ICs  for battery-powered applications provide a logic input to switch the device to a shutdown mode.  This type of shutdown pin can require additional components __ Circuit Design by Greg Dittmer, Linear Technology Corp, Milpitas, CA

Pushbutton Switch Through Glass  -  This simple technique allows a mechanical pushbutton switch assembly to activate a reed type relay through a pane of thick glass.  Pushing the button moves a magnet near the reed relay, closing the relay contacts . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Pushbutton Switch works through Glass -  This simple technique allows a mechanical pushbutton switch assembly to activate a reed type relay through a pane of thick glass.    Pushing the button moves a magnet near the reed relay, closing the relay contacts.   . . . Circuit by Dave Johnson P.E.-February, 2002

Pushbuttons & digital potentiometer control boost converter -  02/17/05 EDN Design Ideas:  Digitally controlled potentiometers are useful for generating analog control voltages under the control of a microcontroller.  in some applications, manual pushbutton switches could replace a microcontroller and simplify product design.  Mechanical switches exhibit contact bounce, and, when a user actuates them, they may open and close many times before reaching a stable state __ Circuit Design by Simon Bramble, Maxim Integrated Products Inc, Wokingham, UK

Quickly discharge power-supply capacitors -  07/05/01  EDN Design Ideas:  A perennial challenge in power-supply design is the safe and speedy discharge, or "dump, " at turn-off of the large amount of energy stored in the post-rectification filter capacitors. This energy, CV2/2, can usually reach tens of jo __ Circuit Design by Stephen Woodward, University of North Carolina, Chapel Hill, NC

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


Switches:  #'s - C       D - L       M - Q       R - S       T - Z


HOME Schematics Index Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches


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