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Author Topic: Needing info on garage door IR beam and interrupt input  (Read 2229 times)
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Hi everyone,
I was wondering if anyone has messed with a IR beam on a garage door. Im building a project and it doesnt seem that the beam is a simple high/low when it is broken. Anyone know exactly how they work.I see a DC voltage on the 2 wires but it doesnt toggle high to low or visaversa. It does change but only a small amount. I would like to use a interrupt input to detect this too.
Thansk for any help
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It might be an open drain output, if it is, it will require a pullup resistor to set it before you see anything...

The IR itself is modulated with a carrier frequency much like a TV remote, maybe 38kHz?

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Hi everyone,
I was wondering if anyone has messed with a IR beam on a garage door. Im building a project and it doesnt seem that the beam is a simple high/low when it is broken. Anyone know exactly how they work.I see a DC voltage on the 2 wires but it doesnt toggle high to low or visaversa. It does change but only a small amount. I would like to use a interrupt input to detect this too.
Thansk for any help

I don't have any specifics, but I do know that garage door manufactures put quite a bit of effort into making it really difficult to disable/bypass them. I don't believe the IR sensors are simple photodiodes, they communicate with the door opener with some proprietary protocol.
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I don't believe the IR sensors are simple photodiodes, they communicate with the door opener with some proprietary protocol.

If this is the case, you might try making your own.
Modulate an IR led at 38khz, use a lens to extend range...

And receive it with either one of these demodualtors, TSOP4038 or TSOP58038.
These two specific parts are rated for continuous use, I found both at Mouser.
Regular TV remote demodulators will stop responding to a continuous signal (over 20% duty cycle) after a short while due to the gain control.
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Got it figured out.
I'm going to post this so anyone else who might want to know this can use it.
The beam does indeed, as i suspected, contain a pulse stream. I found this out by using a scope and I can see the pulse stream. It is running at around 155hz (yes hz). I checked my neighbors and he has a genie garage door opener and his is the same. Now I'm not saying that all manufactures use the same freq, but it is odd that carftsman and genie are the same.
This doesn't pose a problem.
The pulse stream goes away when the beam is breached, so it's either there or not. This makes it simple for the arduino and myself to use.
I'm am going to use a 555 (that's 555 timer) and a make a missing pulse detector, as soon as the beam is breached the 555 will transition, the interrupt in the arduino will see this and I'm on my way.
Thanks all for your suggestions.
Asta bro's
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The beam does indeed, as i suspected, contain a pulse stream. I found this out by using a scope and I can see the pulse stream. It is running at around 155hz (yes hz). I checked my neighbors and he has a genie garage door opener and his is the same.

My garage door opener works great, but pre-dates the safety sensors and I'd like to add one.

Are the sensors simple IR transmitter and receivers with the modulation and detection circuitry on the opener control board or is there active circuitry in the sensors themselves?
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