Skip to main content

Simple Touch Switch Circuit


Description
Similar to the CMOS based Touch Switch also on this site, this transistor based touch switch can activate a load simply by the user touching a metal plate. It is designed to directly switch a relay to allow it to be used with large loads. As it uses only a few commonly available transistors and a 12V supply, it is ideal for hostile environments where mechanical switches would be damaged. Using a latching relay and two of these circuits, a simple two pad "touch on/touch off" arrangement can be made. 
Circuit Diagram

Parts


Part

Total Qty.

Description

Substitutions
R1110 Meg 1/4W Resistor
R2147K 1/4W Resistor
R31120k 1/4W Resistor
R41470 Ohm 1/4W Resistor
C1115uF Electrolytic Capacitor
D111N4007 Silicon Rectifier Diode
Q112N5458 N Channel Field Effect Transistor
Q212N2222 NPN Transistor2N3904
Q312N3906 PNP Transistor
K11Relay w/12V Coil, Contacts To Suit Application
MISC1Board, Wire, Small Metal Pad For Touch Pad
Notes

  1. The touch pad can be most easily made by cutting a small square of PCB material and then soldering on a single wire. Alternatively, something like a penny glued to a plastic backing will do the job.
  2. As mentioned, a latching relay can be used so that a momentary touch activates the relay and it remains active. To turn off a latching relay, power must be interrupted. So a 2nd circuit with a normal relay can be used to cut power (use the NC contacts on the 2nd circuit). Placed side by side, two touch pads form an "on" and an "off" pad.
Source - http://www.aaroncake.net/circuits/Simple_Touch_Switch_Circuit.asp

    Labels:

    Comments

    Post a Comment

    Popular posts from this blog

    Mantis 9 1 CNC Mill

    The Mantis 9.1 design is a radical departure from version 8 and earlier. Most notably, the part count has been almost halved! The current design has 13 parts, all of which can be made with a handsaw and a drill press. Also, I’ve traded away my alignment free exactly-constrained design for extra stiffness. Several unsuccessful attempts to eradicate the last of the slop in the Z axis on version 8 lead me back to the world of over-constrained parallel rods. My previous attempts at an over-constrained design (versions 1-5) all failed because I was unable to make the rods sufficiently parallel to avoid jamming. What to do? [ ]
    Post a Comment
    Read more

    25 Watt Audio Amplifier Circuits Diagram

    25 Watt Audio Amplifier Circuits Diagram Parts: R1 ,R4 _________47K   1/4W Resistors R2____________ 4K7   1 /4W Resistor R3____________ 1K5   1 /4W Resistor R5__________390R    1/4W Resistor R6__________470R    1/4W Resistor R7___________33K    1/4W Resistor R8__________150K    1/4W Resistor R9___________15K    1/4W Resistor R10__________27R    1/4W Resistor R11_________500R    1/2W Trimmer Cermet R12 ,R13,R16 __10R    1/4W Resistors R14 ,R15 _____220R    1/4W Resistors R17___________8R2     2W Resistor R18____________R22    4W Resistor ( wirewound )   C1___________ 470nF   63V Polyester Capacitor C2___________ 330pF   63V Polystyrene Capacitor C3 ,C5 ________470µF   63V Electrolytic Capacitors C4 ,C6,C8,C11 _100nF   63V Polyester Capacitors C7___________100µ F   25V Electrolytic Capacitor C9____________ 10pF   63V Polys...
    Post a Comment
    Read more

    Electronic Extended Play Circuit Diagram

    This is a Electronic Extended Play Circuit Diagram. A single op amp-one of four contained in the popular LM324-is operating in a variable pulse width, free-running square wave oscillator circuit, with its timed output driving two transistors that control the on/ off cycle of the tape-drive motor. The Oscillator` s positive feedback path holds the secret to the successful operation of the variable on/ off timing signal.   Electronic Extended Play Circuit Diagram The two diodes and pulse width potentiometer R8 allows the setting of the on and off time, without affecting the oscillator`s operating frequency. One diode allows only the discharge current to flow through it and the section of R8 that it`s connected to. The other diode, and its portion of R8, sets the charge time for the timing capacitor, C3. Since the recorder`s speed is controlled by the precise off/on timing of the oscillator, a simple voltage-regulator circuit (Ql, R3, and D4) is included.  Connecting the spe...
    Post a Comment
    Read more