figure touch pad

Discussion in 'General Electronics Chat' started by boby4u, Jul 7, 2007.

  1. boby4u

    Thread Starter Member

    Jun 1, 2007
    I am going to make a finger touch pad .
    first of all I wanna get some information about that would you mind giving me some, if you khow any sites?
  2. lightingman

    Senior Member

    Apr 19, 2007
    Hi...Ther are a few ways of doing this.....One is by using the stray hum pick-up from your finger... You just amplify and rectify this to trigger what ever you need to.....The next method is the capacitive one, whereby you send a square wave signal into one input of a CMOS exclusive or gate (4030/4070), then the same signal through a 4.7Meg resistor to the other input (this input also being the touch plate)..... The idea being that when both inputs are high or low, there will be a logic 0 at the output.... When you touch the plate it will alter the time constant of the signal into the touch plate input, causing the output of the gate to produce pulses....The other method is by using a touch plate made in 2 sections and detecting the resitance change when the finger touches the plate...Hope this helps...Daniel.
  3. hgmjr

    Retired Moderator

    Jan 28, 2005
    There are several touch switch example circuits that can be found at . Click on the schematic link and search with the keywords touch switch.

  4. boby4u

    Thread Starter Member

    Jun 1, 2007
    thank you very much .
    I don`t think I could find this information elsewhere.
    I googled the web befor but found nothing.thanks a lot