Need help with idea of “common ground”/ review of my simple circuit

Thread Starter


Joined Feb 25, 2018
Hello all,
Could someone please help me with the below? I am essentially making a device that can raise/ lower my rf projector screen from the 12v trigger port on my projector. The idea is coming from this GitHub.

There are 3 pieces of hardware, green board= rf transmitter, small blue board= 12v to 3v convertor, and Arduino nano.

Below are pictures of what I have done so far. Essentially I don't know if I have it wired up properly and was hoping someone could review it for me. Also, the big thing I'm scared about if the "common ground". Have I wired the grounds properly? If I understand what I am doing, I have 2 power feeds going into this system, 1 from the 12v trigger port and one from the 5v power plug. Am I supposed to have a wire going out of the ground pin of the 12v to 3v convertor to the ground on the nano? Are there issues with my wiring/ grounds in general?

Attached are photos. Thank you all again for any guidance you can provide!!



Joined Apr 11, 2010
One question I have, although not relating to your common ground query, is does your Nano run on 3V? The standard Arduino Nano (and clones) run on 5V. The 3V from your converter may not reliably be read as a logical high or true by a standard Arduino Nano.

Secondly, pictures of wiring are too difficult to read. I suggest that you sketch out how you plan on wiring everything and attaching a picture of that to your post.