Piezo switch problems

Discussion in 'The Projects Forum' started by rgracey, Apr 20, 2010.

  1. rgracey

    Thread Starter New Member

    Apr 20, 2010
    1
    0
    Hello all, I am very new to all the electronics stuff so bare with me. I am building a scuba dive light and I need help with making a piezo switch work. The light is built in two pieces, the light head(torch) and the battery pack(canister). The piezo was chosen due to its extreme durability and waterproofing. The problem i ran into is that the piezo is momentary, and I need to turn it into an on-off switch. How can I accomplish this? Thanks for any help that might be given.
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    Piezo elements are not switches. They make an electrical output while a change in applied force goes on. One would need a circuit to detect the output from the piezo element and that circuit could do the switching.

    Or you can get a watertight box, a toggle switch, and a sealing boot - http://parts.digikey.com/1/parts/984423-switch-boot-waterproof-f-jwl-ser-at4126.html

    You might want to insure the boot was good to your expected depth. Go to the NKK site and search on their part number to get the specs.
     
  3. Markd77

    Senior Member

    Sep 7, 2009
    2,803
    594
    I've got a torch which is turned on by a reed switch. On the outside there is a slide switch type of thing with a magnet in it.
     
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
    1,015
    69
    Piezo switches are quite common in weatherproof, vandal-resistant or ultra long life applications as they have no conventional moving parts.

    Example:
    http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0224350

    Electrically they have a piezo element feeding a bidirectional FET, so emulate a conventional momentary contact push switch.

    To give it On/Off action, you need to use a bistable or one-bit counter, so the output toggles each time it gets an input pulse.

    You could use something like a CD4013 as the bistable, driving a small FET to control a relay (or power FET) to switch the lamp power.
     
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