Step 3: Wiring the transformer

Picture of Wiring the transformer
I used a variable voltage (8-16-24 volt) doorbell transformer made by Heath/Zenith. It cost about $15 at my local home center. You need a transformer that produces 24 volts.

I direct wired the transformer to a grounded, 3 prong plug and mounted it directly above a power strip near my workbench. The 4.7k-Ohm resistor was soldered in place and then secured with a piece of heat shrink tubing I had on hand; it's directly beneath the transformer in this picture.

If you wish, you could cover the wiring with plastic channel for a neater appearance; I simply chose to use insulated staples.

One other thing I did later on was to plug the power strip into a lamp timer, and set the timer so the strip is on only between 8pm and midnight. There's no reason to power the transformer 24/7, as the only critical time is at night when we're going to bed and (presumably) have forgotten to close the garage door. Which leads us to the final step...
mcory2 years ago
You state that there is no reason to power the transformer 24/7 and I agree.

Couldn't you wire this thing to power the transformer only when the door is open? The simplest way might require passing 120v thru your switch.