1. Home
  2. Electronics Design
  3. repurposing garage door beams

repurposing garage door beams

I have a pair of garage door safety beams that I would like to use as some sort of beam detector in a project. Seems a waste to trash these and design something new. The trouble is I can't figure out how these suckers work!

Each one has only two wires going to it. I hooked up a 12v DC and ground to each sensor and I got each to power up and start blinking lights. But with only power and ground, how the heck does it send a signal back to the computer? These are too old to be bluetooth.

I decided to hook up my logic probe to see if there was anything. No pulses at all whether beam aligned or not.

Next I hooked up my DMM and set it to AC. Read 27v AC on each sensor's 12v DC line. That's odd. I don't have a scope so I'm not sure if there is some sort of AC signal being generated (but I would like to have the $4700 Fluke pocket scope if you want to send one as an xmas gift).

Finally I whipped out my camera to see if the IR sensor was glowing. Sure enough it is.

I can't get these open, so I'm not sure what's inside. I already applied Vulcan force and that failed - there are no visible fasteners. Are these the impossible black boxes designed by NASA?

Reply to
Apple Boy
Loading thread data ...

Maybe IR transmitters like you find with your TV remote?

--
"I\'d rather have a bottle in front of me than a frontal lobotomy"

"Daily Thought:

  SOME PEOPLE ARE LIKE SLINKIES. NOT REALLY GOOD FOR ANYTHING BUT
  THEY BRING A SMILE TO YOUR FACE WHEN PUSHED DOWN THE STAIRS.
http://webpages.charter.net/jamie_5"
Reply to
Jamie

Both commons go together. (to ground?) Both positives go together. (to positive?)

Whatever signal that tells the master unit that the slave (receiver) sees the light from the master (transmitter) is superimposed on the positive side.

Try connecting them to a supply, and monitoring the difference in the signal when they see each other, vs when they don't.

Reply to
PeterD

"Apple Boy" skrev i en meddelelse news: snipped-for-privacy@u69g2000hse.googlegroups.com...

They could be designed to run from a current-limited supply so when a sensor detects something it pulls - f.x. 30 mA instead of the usual f.x. 10. Try and stick a 100 Ohm resistor in series with the 12 V and measure the voltage after it (or across - if that is easier).

Reply to
Frithiof Andreas Jensen

Reply to
seegoon99

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.