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Sensors / Detectors: Capacitance / Touch Switch Circuits
Capacitance Switches:   #'s       A-R         S-Z

Sensors / Detectors Main Page
Last Updated on:
Wednesday, June 02, 2021 04:22 AM

Circuits Designed by Dave Johnson, P.E. :
  • Short Range Reflective Object Sensor -  Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch. The sensor uses an inexpensive infrared LED and a matching photo diode . . . [Circuit by Dave Johnson P.E.,  07/09/06]
     

  • Single Output 120VAC 200 Watt Touch Switch -  This simple circuit uses a single IC to form a nice touch switch circuit.   A single transistor forms the remote active switch sensor.   Multiple switches can be wired in parallel.   The switch circuit can be located about 500 feet from the control circuit.  . . . [Hobby Circuit designed by David Johnson P.E.,  02/07/10]

 

  • Solid State Touch Activated Switch -  It does not get any easier if you want a solid state switch that is activated by the touch of a finger. Two small metal pins route voltage through the finger skin to a MOSFET switch. The circuit is great for situations where a membrane type mechanical switch . . . [Hobby Circuit designed by David Johnson P.E.,  06/03/00] 

  • Through Glass Push Button Switch -  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 David A. Johnson P.E.,  11/07/10] 

  • Through Glass Pushbutton Switch -  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 David A. Johnson P.E.,  02/10/02] 

  • 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 Dave Johnson P.E.,  01/18/02] 

  • Touch Alarm for Door Knob -  I designed this hobby circuit many years ago and it seems be a very popular construction project. Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is place . . . [Hobby Circuit designed by Dave Johnson P.E.,  05/29/00] 

  • Touch Switch 240VAC -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/12/02] 

  • Touch Switch controls a 120 VAC load -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/11/06] 

  • Touch Switch Exciter -  If you have hundreds of touch switches that need an excitation signal, then this circuit is what you need. Its 20KHz 20v peak to peak output signal can supply up to 3 watts of touch switch excitation power . . . [Hobby Circuit designed by David A. Johnson P.E.,  02/11/02]


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

Short Range Reflective Object Sensor -  Drawing only 30uA from a 3v supply, this circuit will detect a human finger with a range of about 1 inch. The sensor uses an inexpensive infrared LED and a matching photo diode . . . [Circuit by Dave Johnson P.E.,  07/09/06]

 

Simple Touch Alarm Circuit -  Touch the sensor of the alarm with your finger and it starts beeping, goes on for some time and then stops. Touching it again, and it goes again! This little and flexible circuit consists of a touch sensor and a directly coupled transistor amplifier with a small loudspeaker as the output load. Two sensor strips of metal are. . .  [Circuit Posted by T.K. Hareendran]

 

Single Output 120VAC 200 Watt Touch Switch -  This simple circuit uses a single IC to form a nice touch switch circuit.   A single transistor forms the remote active switch sensor.   Multiple switches can be wired in parallel.   The switch circuit can be located about 500 feet from the control circuit.  . . . [Hobby Circuit designed by David Johnson P.E.,  02/07/10]

 

Solid State Touch Activated Switch -  It does not get any easier if you want a solid state switch that is activated by the touch of a finger. Two small metal pins route voltage through the finger skin to a MOSFET switch. The circuit is great for situations where a membrane type mechanical switch . . . [Hobby Circuit designed by David Johnson P.E.,  06/03/00]

 

Through Glass Push Button Switch -  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 David A. Johnson P.E.,  11/07/10]

 

Through Glass Pushbutton Switch -  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 David A. Johnson P.E.,  02/10/02]

 

 

Touch Activated Lamp -  The circuits below light a 20 watt lamp when the contacts are touched and the skin resistance is about 2 Megs or less. The circuit on the left uses a power MOSFET which turns on when the voltage between the source and gate is around 6 volts. The gate of the MOSFET draws no current so the voltage. . .  [Bill Bowden's circuit]

 

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 Dave Johnson P.E.,  01/18/02]

 

Touch Alarm for Door Knob -  I designed this hobby circuit many years ago and it seems be a very popular construction project. Many companies offer simple alarm devices for personal use in bedrooms or hotel rooms. A metal chain attached to a box holding the electronics is place . . . [Hobby Circuit designed by Dave Johnson P.E.,  05/29/00]

 

Touch Controlled Mute Switch with 555 IC -  Here is another simple circuit to mute the volume of Audio devices through simple touch. It exploits the action of the flip-flops in the timer IC 555 to reduce the volume of the Audio amplifier. IC NE555 is designed in the toggle mode. Its lower and upper comparator inputs are connected to the touch plates which can be. . .  [Circuit Posted by D Mohankumar]

 

Touch 'N Flip -  Ever wonder how a touch plate, like the kind you see on some elevators and lamps work?This circuit will give you a feel for how the touch plate works in a circuit and you can expand on the circuit to suit your project needs. The touch plate. . . .  [Randy Linscott's design]

 

Touch sensistive touchpad -  What to give your next project that distintive 'high tech' look?  Want to do it for under $5?  I make my own single sided boards for most of my projects lately. This board layout was created using the SOIC version of a PIC16F627A without drawing the usual schematic first. Most of the part values are etched on the Layout. The SIP resistor packs I used are 10k ohm, some experimentation with this value may be useful. . . .  [by Luhan Monat-Mesa Arizona]

 

Touch Sensor Switch Circuit with 555 timer -  This is a very simple touch sensor switch that is build with the 555 timer IC. You just need to touch the metal plate and the relay gets energised and is kept in this state for about 100 seconds, then is released. This kind of sensor switch is suitable for making touch operated bells, buzzers of small toys which operate for a. . .  [Circuit posted by Popescu Marian]

 

Touch Switch -  The Touch Switch circuit will detect stray voltages produced by mains voltages and electrostatic build-up in a room. In the first circuit, pin 2 must see a LOW for the circuit to activate. If sufficient static voltage is detected by the plate, the chip will change state. If not, you will need to touch the plate and the 0v rail. . .  [designer's name not found on the website]

 

Touch Switch -  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. . .  [Circuit designed by Aaron Cake]

 

Touch Switch -  This circuit uses a 555 timer as the bases of the touch switch. You can learn more about 555 timers in the Learning section on my site. When the plate is touched the 555 timer is triggered and the output on pin 3 goes high turning on the LED and the buzzer for a certain period of time. . . .  [Randy Linscott's design]

 

Touch Switch 240VAC -  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . [Hobby Circuit designed by Dave Johnson P.E.,  02/12/02]

 

Touch Switch Circuits -  Here is a great collection of touch switch circuits. A touch switch is an electronic device that enables us to control a circuit by simply touching a sensor. Simple touch switch circuit with 4011 – source The circuit as you can see from its diagram is very simple and only uses 8 components. The heart of the circuit is. . .  [Circuit posted by Popescu Marian]

 

Touch Switch Circuits -  All the circuits and projects we describe in these articles consist of very important "building blocks" that you can add to other designs. This time we describe the concept of touching a plate (or two plates separated by a small gap) and turning a circuit ON or OFF. A TOUCH PLATE is classified as a high impedance device. . .  [email Colin Mitchell: talking AT tpg.com.au]

 

Touch Switch controls a 120 VAC load -  This is a capacitance based touch on/touch off switch, which can control power to a 200 watt 120vac load . . . [Hobby Circuit designed by David A. Johnson P.E.,  07/11/06]

 

Touch Switch Exciter -  If you have hundreds of touch switches that need an excitation signal, then this circuit is what you need. Its 20KHz 20v peak to peak output signal can supply up to 3 watts of touch switch excitation power . . . [Hobby Circuit designed by David A. Johnson P.E.,  02/11/02]

 

Touch switch needs no DC return path -  02/03/05  EDN Design Idea   Common designs for touch switches detect a decrease in resistance when a user's fingertip either connects a contact to the circuit's common ground or supplies an injection of 60-Hz ac voltage, resulting from immersion in the electro. . .  [by Brad Albing, Philips Medical Systems Inc, Cleveland, OH]

 

 

Touch triggered alarm -  No description available. . .  [Posted by Jospfh]

 

Touch-Activated Timer Switch Extends Battery Life -  10-Jul-08 EDN Design Idea   Designed to fit into the battery compartment of an optical mouse, this circuit automatically shuts off the battery after a time delay. . .  [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. . .  [Published in Elecktor July/Augu, 2010]

 

Travel Touch Alarm -  The Travel Touch Alarm can be used to provide a audible alarmwhen someone touches the door knob or handle of your hotel room. The door knob or handle must be made of metal for the circuit to work. The main chip in the circuit is a 555 timer. . . .  [Circuit design by Randy Linscott]


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