Turning "on" a device which already has power

Hey guys - new here, and fairly new to electronics (ok…very new).

I just got my Arduino, and was wanting to use it to control my garage door remote. I’ve got the remote pulled apart and have found the two traces that need to be crossed to “press the button”. Would it be simple to connect these two wires to my Arduino and have it do that? The remote’s already powered by one 1.5v AAA battery.

I’ve got the Arduino hooked up to my PC (USB) and have went through a few test programs… Mostly, I’m just concerned that I’ll fry the remote, the board, or both!

Sorry for the noobish post… not knowing most of the lingo, I wasn’t sure what to search for…

Thanks guys!

Since the remote is powered by 1.5V, and arduino would put out 5V on a digital pin, you need to use an optocoupler. This keeps the two parts isolated. Heaps of examples out there.

Ahh - that looks perfect. Which optocoupler should I get (I found hundreds, haha)? I found a good example of how to use it, just not sure which one would be best.

since this not a very timing critical task you can use most or any ("standard") optocoupler to do this. because they're cheap and always available where i do my shopping i swear on 4n28's.

you could even (and i tend to recommend that) build your own: connect a photo diode across your button. like that in can be "pushed" with just light, or better with a blink of an LED connected to your board.


Wow - good advice. Thanks so much! I'll be sure to let you know how it goes!

Thought I'd report back with my progress on this:

The optocoupler works great! Since then, I've nearly finished this project. I've now got my Arduino listening for serial input from my Ubuntu box. When it receives the "open" command, it opens the garage door, and replies with "Garage Door Open!". I was initially worried about the usb/serial communication, but that was no problem.

I ended up configuring /dev/ttyUSB0 for the Arduino, then just echoing the command to that tty.. In another window, I just tail the tty to get the serial response. In front of that, I set up a simple php script to run my root command (which echo's the "o") via a secure web form.

It probably sounds chaotic, but it's really quite smooth. Works great!

Thanks again for your help guys.


Could you have used a transistor to open/close that circuit? just an idea.

An optocoupler is a photo-transistor no? I'm a noob when it comes to electronics.. Odds are there was an easier way to approach this. heh..

An optocoupler is no more than a LED and phototransistor in a dark box. When the LED is lit, the phototransistor fires up. The reason they are used is the two circuits are not electrically connected, where they are in standard transistors, protecting it from power surges. I would have thought a transistor would have been easier and i would have figured only to use an optocoupler only for special applications where its protection is needed, but hey, i guess it works.

Yeah sorry my bad. Just when I see a problem like this the first thing that comes to mind is a transistor like the TIP120. Octocouplers seem pretty neat though.