I have a remote rf garage door opener that I want to wifi enable.
The unit is normally used at 12v, but is capable of doing its job at 5v too.
I tried it with 3.3v, but that did not work.
Anyways, I have soldered some wires to the battery poles (+ and -) of the remote, as well as the switch on the unit. The plan is to override the switch using a gpio from an nodemcu.
However, since the remote only operates at 5v or higher, I have a problem..
I could easily power the nodemcu with a usb-cable, then the remote by connecting it to ground and V-in on the nodemcu (giving me 5v) , but I still have not figured out how to trigger the switch that requires 5v, since the nodemcu only gives me 3.3v...
I was thinking of using a relay, but it feels a bit overkill, and also the one I have already is actually rated for 5v
For a real electronics noob, what can I do? And exactly what part can I use to solve my challenge?
You are showing four wires, but two of these should be common; connected to the same point.
You need to detail the actual circuit inside the remote in order to make sense of how to control it.
Otherwise, you are indeed restricted to the cumbersome and inefficient approach of using a relay.
Your description is unclear. You mean to say as I understand it, that the remote is operated from a 12 V "lighter" battery but you have tried it on 5 V instead and found it works; presumably with greatly reduced range.
For a switch you usually have a pull resistor to one side of the rail and a switch that shorts to the other side. First thing you should do is find out what happens here. Pullup and short to GND, or pulldown and short to VCC.
In the Pullup case, you can use a normal NPN transistor, and in both cases, you can use an optocoupler.
