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Membrane and/or tactile switches for 3 way hi/low/off settings?

Discussion in 'General Electronics Discussion' started by chadecoen, Sep 30, 2015.

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  1. chadecoen


    Sep 30, 2015
    Hello everyone. I have been googling and what not and can not seem to find some sound advice for my project. Hope someone here can point me in the right direction.

    I am installing heated seats in a vehicle that did not come with them. I want to use a factory dash switch. Unfortunately. OEM switch is not really a switch but only sends signals through the canbus system and doesn't actually turn on the seats.

    I looked behind the switch and there is a PCB in there and very limited room between the actual button you press and the board behind it. I want to use this switch but skip out the canbus system and have it turn on the seats directly. I have just about enough room for a tactile or membrane switch in there.

    The heaters came with rocker switches with off/low/hi settings.

    1. How do I make a tactile or membrane switch do those 3 settings? Am I going to be learning Arduino soon, hahaha?

    2. I know they are for very small amps, well Ma anyway. Much less than the heaters require, even for the relay trigger I suspect. I think (and I am just thinking out loud here) I can knock down the amps via some sort of resistor and have the tiny switch power some micro relays that in turn could trigger the large relays the kit came with? Am I on the right path?

    I am probably not making a whole lot of sense here but does anyone understand what I am trying to do? Any ideas best way to proceed? I basically want to replace this seats/switch.jpg with a tactile or membrane switch but need it to have settings similar to this (and unfortunately I can't buy that last switch by its self!)
  2. BobK


    Jan 5, 2010
    How is the heater wired? Are there two positive leads, one for low and both activated for high?
    Assuming it is like that:

    What you would need is some logic and two relays. The switch would pulse the logic to advance to the next state: off -> low -> high -> off. The switch needs to be debounced or it will go multiple steps each time you press it. You could use discrete logic chips:2 flip flops, or a decade counter configured to reset on the third press. Or, you could use a microcontroller The relays might need an additional transistor to handle the coil current.

    Arouse1973 likes this.
  3. chadecoen


    Sep 30, 2015
    Thank you, Bob! I'll have to look when I get home but I think it has 2 pos leads like you said.

    I knew someone wiser than I could send me off in the right direction.

    I'm off to learn some logic, haha.

    Arouse1973 likes this.
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