Project idea AC Control - Is it possible this way?

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Mizza
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Joined: Sun Oct 20, 2013 2:49 am

Project idea AC Control - Is it possible this way?

Post by Mizza » Mon Oct 21, 2013 7:58 am

Hi,

Just got my experimenters kit and I'm lovin it - thanks!

Thinking ahead for down the road I'm just curious if this concept is pheasible without wasting hours researching a dead end, when I could've spent it thinking of something else.

I want to automate our aircon (evaporative cooler) just by temperature sensor initially; some web interface in the future. But seeing as I've just bought an experimenters kit dictates I don't want to/shouldn't go anywhere near 240V or mains power.

My question is though can I just mimic the pushing of the buttons on the the control panel? It's hardwired to the wall with a couple of buttons and a dial connected to a circuit board (4 wires, 24V I assume~?, or at least not 240V!! - slightly older style, no LCD display or anything just a few LED's). If I can determine the power button etc with a multimeter could I just solder the arduino (with relays or whatever required) onto the same pins of the AC control panel and control it that way?

Have done a lot of Googling on this and found a slightly similar setup but nothing confirmatory. Still a complete noob so though bugger it I'll just ask. I'm an experienced network tech but with no electronics experience. So the coding side I'm finding relatively simple (so far), now just need to wrap my head around the electronics side.

Thanks

andrew
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Re: Project idea AC Control - Is it possible this way?

Post by andrew » Mon Oct 21, 2013 9:27 pm

Yes, you're on to something there. A simple way is to use what's called an optocoupler, typically a type 4N25. It can be used as an isolated "bridge" between an Arduino output and an existing button on something.

Here's a neat explanation about them:
www.jaycar.com.au/images_uploaded/optocoup.pdf‎

Mizza
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Joined: Sun Oct 20, 2013 2:49 am

Re: Project idea AC Control - Is it possible this way?

Post by Mizza » Tue Oct 22, 2013 7:35 am

Cheers, johnb. Just the answer I was looking for. Thanks for the tip too, I had seen the term octocoupler come up a fair bit in my searching. Time to get my research on and more practise.. Thanks again.

andrew
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Re: Project idea AC Control - Is it possible this way?

Post by andrew » Tue Oct 22, 2013 7:41 am

Mizza wrote:Cheers, johnb. Just the answer I was looking for. Thanks for the tip too, I had seen the term octocoupler come up a fair bit in my searching. Time to get my research on and more practise.. Thanks again.
No worries. Another very simple and safe method of controlling mains current is to get one of those wireless powerboard things, and hack into the remote - replacing the buttons with 4n25s controlled by Arduino digital outputs.

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