How to turn on this button without pressing it

Discussion in 'General Electronics Chat' started by Pashgen, Jan 13, 2018.

  1. Pashgen

    Thread Starter New Member

    Nov 16, 2017
    17
    2
    Hi!

    Looking for some help with switching on small dehumidifier without touching power button.
    For my project I need to connect dehumidifier to relay. And its all good BUT
    i don't know how this switch on dehumidifier works (see attached pictures).
    Basically, dehumidifier will be control by Arduino thru relay. So when relay sending power to dehumidifier it should turn on instead of waiting for me to
    press power button on it.

    Could you please help

    Here is pictures WP_20180114_13_48_53_Pro.jpg WP_20180114_13_49_38_Pro.jpg WP_20180114_13_50_53_Pro.jpg
     
  2. WBahn

    Moderator

    Mar 31, 2012
    22,865
    6,829
    Most likely you can just swap out the switch with a suitable solid state relay or even just an optocoupler.
     
  3. Pashgen

    Thread Starter New Member

    Nov 16, 2017
    17
    2
    Yeah! That would be perfect!
    Could you please tell me what contacts I can use to turn it on and off with the help of relay. I mean - there are 4 contacts to that POWER Button,
    which 2 contacts I can use to send there +9V and switch on dehumidifier?
    Should I take that power button out?
     
  4. cmartinez

    AAC Fanatic!

    Jan 17, 2007
    5,358
    6,284
    That sort of button only has two contacts, divided into 4 terminals.

    [​IMG]
    https://www.digikey.com/products/en?keywords=SW400-ND

    The two terminals on the top are a single contact that connect to the two on the bottom when the button is pressed

    upload_2018-1-13_21-33-0.png
     
    Last edited: Jan 13, 2018
  5. WBahn

    Moderator

    Mar 31, 2012
    22,865
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    Most of those kind of switches only have two electrical contacts. The four physical contacts are connected in two pairs. In the picture of the top of the board, the two legs on the right side of the switch appear to be the two electrical contacts. If you have a voltmeter you should be able to verify this by measuring the voltage across the pair and seeing it go to zero when the button is pressed.
     
  6. Pashgen

    Thread Starter New Member

    Nov 16, 2017
    17
    2
    YES!!!!

    It worked!!!

    Sorry about late reply, got side tracked and couldn't test it right away.

    Thank you so much everyone!!!

    Cheers,
    Pavel
     
    cmartinez likes this.
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