Garage door opener hacking

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frankv

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# 243911 8-Jan-2019 16:33

I have a little project to mount my garage door opener in my car, and power it from the car's 12V supply. The door opener is powered by a couple of coin batteries in series, for a total of 6V. I plan to run a couple of wires in parallel to the pushbutton the PCB to another button on the dash somewhere.

Also, following some comments on here, I'm a bit leary about a cheap AliExpress buck converter, which might fail and put 12V across my only door opener and fry it. But given the (I assume) low current and intermittent use, power efficiency isn't a big deal. I'm assuming that the door opener only uses current when the button is actually pressed. Any idea about that?

So, would a LM7806 linear converter be OK? Do they fail safe? I prefer a fixed voltage anyway.

Bung

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# 2156529 8-Jan-2019 16:58

Would the remote work on 5.something v out of a cig lighter USB charger. You probably have several for phones long obsolete.

Gordy7

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# 2156552 8-Jan-2019 17:15

I have successfully used this Jaycar remote for my garage door and automatic gate.

Rolling code security.

Fobs have never needed a replacement battery over 4 years.

https://www.jaycar.co.nz/4-channel-wireless-remote-control-relay-with-2-key-fobs/p/LR8824

Gordy

frankv

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# 2156635 8-Jan-2019 19:35

Bung: Would the remote work on 5.something v out of a cig lighter USB charger. You probably have several for phones long obsolete.

I'm reluctant to go to a lower voltage; my understanding is that range is proportional to voltage, and I like the idea that I can press the button at the corner, and by the time I get to my garage the door will be up. :)

k1w1k1d

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# 2156674 8-Jan-2019 19:47

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Silly question, but why would you go to all the trouble of connecting to the car battery, when the original cheap coin batteries will probably last for years?

blakamin

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# 2156682 8-Jan-2019 20:24

What brand is your door motor? I got 2 spares for my only one (came with the house) off ebay for $13 and programmed them myself.

My car has a door opener built in, but it doesn't get parked in the garage.

phrozenpenguin

361 posts

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# 2158091 11-Jan-2019 12:12

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k1w1k1d:

Silly question, but why would you go to all the trouble of connecting to the car battery, when the original cheap coin batteries will probably last for years?

This was what I was going to ask..

nickb800

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# 2158092 11-Jan-2019 12:18

Wouldn't you be better off adding a longer antenna to both your remote and door opener, to extend the range?

tripper1000

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# 2158100 11-Jan-2019 13:07

frankv: So, would a LM7806 linear converter be OK? Do they fail safe? I prefer a fixed voltage anyway.

Yeah, linear converters are good for small loads like this. I like them because they are cleaner and easier to filter than the cheap buck converters which can generate noise at high frequency which can interfere with RF receivers, but probably not so much of an issue at the transmitter end.

If you go the buck route it is easy to put in a safety circuit to protect your transmitter from an over-volt. Just chuck a 0 ohm resistor (or tiny fuse) in series with the 6 volt supply, and a 7 volt zener diode across the 6v rail. If the volts go too high, the zener will shunt the current and blow the fuse.

The 5v USB charger will probably work, but I wouldn't be surprised if you loose some range in the same way that you do when the remotes batteries are going flat.

If I were you, I'd modify and test the remote before going to the trouble of dismantling the car just in case the remote buttons are not in an exclusively DC part of the circuit and the circuit goes off freq or does something weird when you add extra wires into it. I've seen older remotes where it looks like the switch is in the oscillator part of the circuit.

Edit: In my experience linear regulators fail open circuit.

frankv

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# 2158314 11-Jan-2019 15:03

More info... I'm planning on mounting this in the car, in a 3D printed replacement for the ashtray, all out of sight except for the button. Also in the same spot will be a USB supply for my wireless phone charger.

Why connect to the car battery? Well, why not? Constant voltage power supply, no batteries to change. There's only a couple of inches of extra wiring needed, plus a $1 circuit board. Should pay for itself in under 10 years in saved batteries. ;)

Good point about the location of the switch in the circuit... will investigate!

Coil

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# 2158316 11-Jan-2019 15:05

blakamin:

What brand is your door motor? I got 2 spares for my only one (came with the house) off ebay for $13 and programmed them myself.

My car has a door opener built in, but it doesn't get parked in the garage.

What? The E38 or E70? Homelink right?

DeepBlueSky

437 posts

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# 2158409 11-Jan-2019 16:47

Throwing it out there maybe go IOT, https://www.tomsguide.com/us/best-smart-garage-door-openers,review-4476.html

gareth41

627 posts

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# 2159413 11-Jan-2019 17:59

All you need is a series resistor to limit the current and then a 6v zener diode and bypass capacitors across the input and output. Use 100n and 10uF caps on either side to get rid of any ripple. I put one of these garage door openers on a spectrum analyser once and found it was operating around 27MHz.

frankv

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# 2159487 11-Jan-2019 21:24

DeepBlueSky:

Throwing it out there maybe go IOT, https://www.tomsguide.com/us/best-smart-garage-door-openers,review-4476.html

Thought about that, but (a) I'd rather hack my own, probably with an ESP8266, and (b) I don't (yet) have anything in the house to automate, and (c) I'm far too stingy to spend US$121+shipping on a garage door opener.

Would be kinda cool and not too difficult (but not very practical) to use my phone to talk to an ESP8266 in the car that pulls a relay to close the garage door remote's button contacts.