The Robot Light Switch

Automating your home is an awesome endeavor — but playing with mains AC can be risky business if you don’t know what you’re doing. So why not play it safe and make use of your light switch?

Admittedly, it wasn’t because [Tyler Bletsch] didn’t want to mess around with AC directly, but rather out of necessity. You see, he just moved into a new office and his “smart” air conditioner… doesn’t turn itself off at night.

There’s a remote control to set the target temperature, but the unit isn’t smart enough to turn off at night. Instead, there’s a physical wall switch so you can turn it off with your actual physical hands, like a barbarian.

Refusing to be a barbarian (and to stay at work late), he decided to simplify the problem by building a servo driven light switch plate. It’s not the prettiest — but it does the trick.

He designed the bracket in Thingiverse to mount a standard 9g servo motor to do the flipping. An Arduino Nano controls it, but since you only need one output pin to run the servo, you could easily use an ESP8266. He went ahead and added a small OLED screen and a few buttons too — he’s using this as a timer to control the A/C unit, but it’s begging for a web dashboard, right?

Alternatively, you can mess with AC directly with this hack using a Raspberry Pi — but you should probably own the place your planning on “upgrading”.

24 thoughts on “The Robot Light Switch

  1. There recently was a successful crowdfunding project called Switchmate, which did the same thing in the same way =) I highly suggest checking them out if you’re interested in non-invasive portable light switching solutions but would rather buy it than DIY.

      1. I should have worded better, I didn’t intend to make it sound like it was for a regular wall socket. For example what I made was essentially just an extension cord.

        Used just used a double sized outlet box with a standard AC socket. Used the free space where the other AC socket would be to place a small high current hermetically sealed relay I had laying around. used a DIN connector on the side to drive the relay.

        I guess you could argue working with AC is dangerous, but I wouldn’t call my method invasive.

  2. i am always impressed by the fact that today people in hobby electronics are not aware of the triac.
    When i was young, this was the first thing you learn. So we were not afraid of AC 230V

    1. There are places where messing around with the AC is not possible, like when you do not own the place and do not have permission from the owner. In any case it does not hurt to consult with an electrician (or at least the net) before playing around with the AC, if only to make sure you’re doing things properly according to the building laws of your location. I’ve never seen it happen but I would think that insurance companies could be difficult in case of electrical fire in places modified by a non licensed electrician.

    1. It might be able to get away with less because of the thickness of the physical switch…

      But My main complaint is that the method he uses makes it difficult or impossible to use the switch manually. When I did a similar project ( I found myself giving a fair amount of thought to making things that would flip or pull switches without getting in the way if I wanted to do it by hand.

  3. Turning lights on & off is such a basic home automation task. However, it seems that the current solutions are to either hack something together or buy one of the big ugly X10 type boxes that plugs into an outlet. Is there anyone yet that sells replacement switches & outlets that we can put in the wall to replace the ones we have? Preferably something AllJoyn enabled that we could program ourselves over WiFi. If anyone has any links, please post them here or PM me. Thanks!

      1. They can work. They’re just not ideal since they require a hub of some sort to access them from a network. There are now several options for WiFi controllable light bulbs but I haven’t yet seen a WiFi controllable switch or outlet. AllJoyn enabled WiFi switches & outlets would enable probably 75% of all home automation tasks without requiring special appliances & bulbs.

  4. Very cool hack? But in this case… wouldn’t using the arduino as an ir blaster be more effective to send a power off/on signal at closing time and again in the morning? He said the AC unit has a remote – surely the remote has power on/off button?

    Also – with electronic controlled AC units like this – do they typically go to ‘run’ state after cycling the mains power? IIRC the one we had at home, if it ever got unplugged while on, would then need a press of the power button to start again.

  5. You can buy drop in switches that have a bluetooth module which talks to a battery powered light switch. I wouldn’t think the protocol would be hard to reverse, or just use a uC to pull the appropriate switches low/high to use the existing controls. They run 20-50USD. If you can reverse the signal you can even still use the switching unit they come with.

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