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

 

Most likely you can just swap out the switch with a suitable solid state relay or even just an optocoupler.

 

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?

 

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?

That sort of button only has two contacts, divided into 4 terminals.

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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

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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.

 

YES!!!!

It worked!!!

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

Thank you so much everyone!!!

Cheers,
Pavel