Wednesday, May 17, 2017

Open sesame!

We have a keypad on the garage door trim that lets us get into the garage. It chews through batteries, so sometimes when I need to get to my car I find that the door won't open, and then I need to go back up and get the garage door remote. But now, so long as I have my phone, I can open the garage!

This is the magical circuit that lets me do that, neatly attached with velcro to the side of the opener. Inside the box, the parts are attached to plastic standoffs that I've glued to the inside of the box with a glue gun. I've also used the glue gun here and there for strain relief and to seal cuts I made in the sides of the box to let wires in and out.

This is the part on the right. The knotted cord is from a 5v charger (I chopped off the micro-USB plug). The other three wires are 5v (red), ground (black) and signal (yellow). The bit in the middle is a bluetooth low energy (BLE) development board, which I've attached to a bit of strip board with a socket so that I can easily take the BLE board out for reprogramming if necessary. I programmed the board with a lightly modified version of some code someone else developed. I used the mobile phone app that this other guy wrote as is, other than changing the "secret key." All communications between phone and the BLE board are encrypted.

I tested the BLE board with an LED on a tiny breadboard standing in for the garage door opener.

The final piece of puzzle is taking the signal from the board and using it to open/close the garage door, which is accomplished with this relay. The output of the relay is wired to the back of the opener, along with the wires for the hardwired button in the garage, and the wires for the wireless receiver for the keypad on the outside of the garage. The entire project is encased in a plastic box that I bought on Amazon.

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