Instructables

Persistant appliance power button

Picture of Persistant appliance power button
When the building looses power, and then eventually turns back on, our portable A/C unit doesn't turn back on. You have to manually push the button on the front of the unit, or hit the power button on the remote. Our A/C unit happens to be in our server room, and bad things happen when it's turned off for too long.

I put together a few simple devices to turn the A/C back on in the event of a power loss. It persistently tries to turn the A/C unit on, and won't stop until it sees that the A/C unit is turned back on.

Parts you'll need:
Christmas light day/night timer - $15
MK111 interval timer - $15
12v dc power adapter - $?
12v dc buzzer - $3
Tape -$?
spare wire - $?

You'll also need some basic soldering skills to put the MK111 interval timer kit together and solder a few extra wires in the remote control, and the Christmas light timer.

 
Remove these adsRemove these ads by Signing Up

Step 1: Hacking the lighting timer

I had an old Christmas lights day/night timer laying around. This was the first step for me in creating this. I don't have the detailed step / pictures that went into this, but it's fairly strait forward.

This is your typical "Christmas Light" timer. It has a "Dusk to Dawn" feature. When it senses there is no light, it will power the plug at the bottom, and when it sees light, it turns the plug off.

First I ripped out the light sensor (photocell) and soldered an extension for it so I could attach it to the A/C unit. The other reason to rip is out was that  I needed to isolate it from any outside light.

Then I taped the photocell to the "cool" LED on the A/C unit. This LED light is only on when the unit is on. I used black electrical tape to make sure it could only see light from that LED. Then I used the stickiest tape that I could find, and taped over that. I also taped the wire down for a short distance in case somebody snags on the wire.

Once that is complete, this circuit will only turn on if the A/C unit is turned off. And once the A/C unit is turned on, the plug will turn off.

Next is the device that turns the A/C back on.

Easiest way to increase time between cycles would be to swap out resistor R1, which should be 1k, with a 10Meg resistor. That should give you about 10min cycle time. If leakage of C3 is too high that time could be considerably less.
Pro

Get More Out of Instructables

Already have an Account?

close

PDF Downloads
As a Pro member, you will gain access to download any Instructable in the PDF format. You also have the ability to customize your PDF download.

Upgrade to Pro today!