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Wireless Garage Door Sensor

Garage Door Sensor switch

Garage Door Sensor switch

This project came about for two reasons. First and foremost I’ve got a detached garage where it’s difficult to see from inside the house if the garage door is open or closed. After multiple incidents of accidentally leaving the garage door open all night long, I knew I had to do something different.

Then, Hack-a-Day posted this article on a Open Garage Door Indicator for under $6, with a challenge to make a wireless version. Never able to pass up a challenge, I started designing…

Off to my favorite place, SparkFun , to look at cheap wireless interfaces.  What caught my eye was the WRL-08946 / WRL-08949, transmitter / receiver pair.   Less than $4 for the transmitter and $5 for the receiver.  OK, so I won’t make the less than $6 challenge from Hack-a-Day, $9 for a transmitter/receiver pair is pretty dang cheap and 434Mhz/2400 baud aught to have been more than sufficient for signaling a switch open/close.

Comments on the SparkFun site seemed to indicate that some people were having problems getting this chip pair to work and that it might well be the automatic gain control causing the receiver to pick up trash data unless there was a continuous stream of transmitted data stream.

Armed with this information, I decided that I would start  by using a pair of ATTINY13’s to encode and decode a continuous  data stream.  This in theory would get around any automatic gain issue and with some error correcting code would be able to recover from a missed bit every now and then.

Thus, on to the detailed assembly….


First a simple hardware layout.    An ATTINY13 creates a data stream, sends to to the transmitter on one board.  The receiver on the 2nd board picks up the signal, sends it to the 2nd ATTINY13 for decoding.  Finally the ATTINY13 controls 2 LEDs, one fora  Door Open/Closed, the indicator, the other LED to indicate loss …

1 comment

    • kfcws on July 10, 2010 at 2:09 pm

    Absolutely fantastic,

    I know it’s common tech you are using but get a patent on this idea ASAP (Warning if door left open).

    Surprisingly, there are no garage door firms that have this. I only know as I was talking to a door engineer today and asked them about it.

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