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We moved earlier this year.  In many, many ways, it was a big step up from the old house.  However, one decidedly step down was going from a house with a 2 car garage to a house with a very narrow carport.  Besides the obvious differences, there was a major annoyance.  The carport didn’t have any lights.

That was rectified over Thanksgiving weekend with the installation of 8 spotlights.  Now, when the lights are on, it feels like you are standing on the beach at midday.  One minor problem with the setup, though.  The lights need to be turned on by a switch near the AC units.   Doesn’t really work all that well if you are driving into the garage and you can’t see anything.  We won’t stop, get out of the car, turn the lights on, and get back in to drive into the carport.

A remote solution was needed.  With the garage, you simply pressed a button and the lights came on(and the garage door went up and down, but that’s not really applicable in the current situation).  That’s what I wanted to happen here.  I scoured the internet, looking for a solution.  There are some remote devices like this one pictured to the right. And I suppose it would’ve worked alright except for a couple of things.  First and most important, only one remote.  I needed at least two and preferably four.  And secondly, they don’t get good reviews.  Typically there are 2 or 3 really bad reviews for every good one.

What to do?  Well, DIY, of course!

I hopped on over to Allelectronics.com, a great website for hobbyist/experimenter/tinkerers.  There I found a great remote controlled relay.  It consists of a couple of on/off keychain switchs and a box with a bunch of wires.   I ordered it that minute with a bunch of other parts to put together my homemade switch box.

Once the box arrived, the first thing I did was take everything apart to see how it worked. The two receiver photos show what’s inside the black box with the wires coming out.  Basically it’s some wireless logic, that feeds into a PT2272 decoder (click for datasheet). This has decoder has an address set using 8 of its pins.

On the right, you can see which of these pins are used to set the address in this implementation.  It only uses 3 of the 8 pins and the rest are no-connects.

The transmitters are small, keychain switches with an on and off button.  Since the receiver latches the state of the last input that it has received, both an on and off are required, unlike a garage door transmitter that only has one button.

Inside the transmitter is a single pcb with a couple of buttons (on and off), an LED, an IC and an RF transmitter.  The IC is a HS2262A (click for datasheet, it’s in Chinese, but pinout is good.)

On the back of the board, you can see that the address bits are setup to match the ones on the receiver.  Why is this important?  Well, if I want to get more transmitters (say, one for guests and one for inside the house), all I need to do is re-solder those bits to make them match the receiver.

Once I had a good understanding of how everything worked, I started putting it all together.   Using a small project box, I installed a 12V input from a wall transformer, and wired it to the input of the receiver.  The output of the receiver was then wired into the input of the relay I am going to use for the actual turning on and off of the lights.  The circuit breaker is in there to give me a little piece of mind once the thing is hooked up to them AC line.

I had a neat surprise when I opened the relay from the box.  It’s in a clear box, which makes it really easy to see what’s going on inside.  Here’s a close up of the relay with the basics of how it works.  You can see the copper switch inside is shorting the left two pins.  When 12V is applied to the switching input, the little blade moves to the right pin and shorts those two.  I know, I know, it’s sad that I find this stuff so cool, but what can I say.

Next up, I need to wire in the AC power so the relay turns it on or off.

Tags: DIY, Electronics, garage, homeowner

This entry was posted on Tuesday, December 8th, 2009 at 8:15 am and is filed under DIY, Joys of the Homeowner.