I have a new vehicle. It does not have one of those systems where you program your remote into it and can open and close your garage door. I must use a battery powered remote and keep it handy but out of sight. I'd like to power it directly from the car electrical system. One thought I had was to use 15 diodes (1N4007) and a 47Ω resistor to drop the voltage. That would drop my voltage to a range of 3.5 volts to 3.9 volts. The remote operates on a single 2032 coin battery, so it doesn't take much power.

Another thought I had was to use one of those cheap USB chargers you plug into a cigarette lighter. But it puts out 5 volts. The whole problem is that I'm cramped for space. The space is 8 cm deep x 7.2 cm wide x 3.5 cm high and tapers back to approximately 6 cm wide x 3 cm high. So whatever I do has to fit in that small space.

One thought I have is that using a USB adaptor along with my GDO remote, the coil on the adaptor might interfere with the radio transmission of the remote. All thoughts and opinions welcome. I know not what I am about to do.

I COULD mount the adaptor away from the remote, but then I'd have to find a place to stuff it under the dash. Not a difficult matter, but one I'd like to avoid. Maybe I should shield the adaptor from the remote. If so, with what? A sheet of copper (which I have). Should the shield be grounded? Lots of questions I don't have the answer to.

 

Seems like too much work for something that needs the battery replaced every couple years on average..
I'd change the battery once or twice if that before I'd likely be getting rid of the car anyways..

Interference is likely to be a non-issue no matter what direction you decide..

If you really want to tackle this project there are simple 12V to 3V dc converters all over the internet..
https://www.amazon.com/SMAKN®-Converter-Power-Supply-Module/dp/B00ODL140M

 

Why do you want to go to all the trouble of eliminating the battery?
Normally they last for a very long time in such intermittent use.

 

Why do you want to go to all the trouble of eliminating the battery?
Normally they last for a very long time in such intermittent use.

I have to hold the remote up to the window to get the door to operate when the battery is down on power. Not dead, but just down. Rather than having to pull it out of the glove box and press a button I'd like to have a button on my dash and just tap that. Installing it into a fixture would solve some of that trouble. Besides, I also have a small volt meter to put on the panel. The meter is 2.8 cm diameter and only 1.2 cm deep. Would hardly eat up any space. Since I want the meter in there, having the remote stuffed in there as well with sufficient power, can open the garage door from all the way out in the street. In fact, a couple doors down.

Not that I care about replacing batteries, it's just that IF I mount it to the car's electrical I have more than enough power. Especially if I run it at 5 volts. Heck, I could probably open my door from the next block over.

The idea of dropping voltage via diodes is one route. I have plenty of these silly little diodes laying around, so no cost involved. Also, as mentioned, I have a couple of those cheap USB adaptors. They're tiny and can deliver plenty of power. Off hand I'm not sure what a 2032 battery has for current, but I think it's probably around 300 mA. Probably not, but the car can deliver plenty of current. So I'm just wondering about this new project. And as for keeping the car, it's brand new, and I think I'll be keeping it for several years. Possibly as many as 10 years. Why not make it the way I want it?!

 

If you really want to tackle this project there are simple 12V to 3V dc converters all over the internet..
https://www.amazon.com/SMAKN®-Converter-Power-Supply-Module/dp/B00ODL140M

Nifty. But its dimensions are 3.9 inches by 3.6 inches by 1.5 inches. Lots bigger than the space I have.

Wondering what would happen if I powered the remote from a 5 volt source. Would it pop? Would it be short lived? Would it have no problems?

 

Look! I have junk laying around. Why not put it to use? If I can bodge together an outboard motor with a weed whacker - - - . OR vice versa. Use a weed whacker as an outboard motor. Just a lot of junk laying around. I say "Use it if you can."

My dad grew up in the great depression. He learned to make things out of what was at hand. He taught me to do the same, and it has been quite useful over the years.

 

As we don't know any details about the GDO we cannot answer if 5V will be ok or not..
Likely not.. but thats just a guess

 

I've found that adding a resistor into the voltage sense circuit I can lower the voltage output to 3 volts. With very little experimentation I've stumbled across the fix to change a 5 volt USB Adaptor to put out 3 volts. I've thrown a 3.3 KΩ resistor into the sense circuit, jumping across the 4.7K precision resistor. They're using a MC34063 DC to DC converter. By paralleling the 3.3K across the 4.7K I'm dropping the resistance to 1.94KΩ, and the output voltage drops to 2.99 volts.

So with just a quick throw of a resistor at it I've modified my output from 5 volts to 3. Now, if I can find a T403 3.3KΩ surface mount resistor I can throw it on top of the 4.7K and call it a done deal. See what can be done with junk?!

 

You could probably tweak the voltage a little higher, like 3.3V to 3.5V to improve the transmission range some, unless it's satisfactory with 3.0V.

 

Actually, tests in my basement, which should not cause the garage door to actuate show that on a 13.8 volt Radio Shack power supply, I'm getting plenty of power to actuate the door. I had to run up stairs to see if the door opened. It did. So now I have a working circuit. But thanks all. I'm going to build this thing up and make it compact.

I'm still wondering about whether I need to shield my power supply from my transmitter. But tests should clarify that issue.

 

I just placed an order for some LT3045/3042 regulators. Quiesient current is low enough.
http://www.ldovr.com

Aliexpress and ebay have some different designs. You would need some front end protection on it. Linear technology's surge stopper series would be ideal. The xmitter may need a large capacitor in place of the battery.
You can parallel them with the expense of increasing Q current.

In the new-fangled cars, it might even be hard to find an ACCY source of power.

 

Volt gauge and garage door opener remote are installed and working nicely.