## Down convert +24DC to 5V

user0068334
Posts: 1
Joined: Mon May 20, 2019 12:24 am

### Down convert +24DC to 5V

Hi all!

I was going to turn one of the Pis I have into a wireless remote for my garage door following some tutorials online (first ever use with GPIO).

It all seems fairly basic on the backend stuff but I wanted to know what the repercussions would be in my situation:

I have 4 terminals on my garage door motor:
1. Wall switch 1
2. Wall switch 2
3. COM
4. +24VDC

I was going to get a DC converter to go from 24V to 5V for the Pi, but then started getting confused because the terminal is only +ve 24V and there's no -ve terminal.

What would happen if I plugged it into the DC converter without the negative half? Would I fry the Pi, or would it not be complete and just not work?

dl324
Posts: 119
Joined: Mon May 06, 2019 7:33 pm
Location: Pacific Northwest, USA

### Re: Down convert +24DC to 5V

-ve could refer to a negative supply but, in your case, it probably means ground. Measure the voltage from +ve to GND, I suspect you'll get 24V.

Gavinmc42
Posts: 3168
Joined: Wed Aug 28, 2013 3:31 am

### Re: Down convert +24DC to 5V

COM is short for COMmon ground.
I'm dancing on Rainbows.
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scotty101
Posts: 3596
Joined: Fri Jun 08, 2012 6:03 pm

### Re: Down convert +24DC to 5V

dl324 wrote:
Mon May 20, 2019 12:36 am
Wrong answer. Nothing would happen because there wouldn't be a complete circuit.

In this case the COM pin should be used as ground
Electronic and Computer Engineer
Pi Interests: Home Automation, IOT, Python and Tkinter

davidcoton
Posts: 3792
Joined: Mon Sep 01, 2014 2:37 pm
Location: Cambridge, UK

### Re: Down convert +24DC to 5V

scotty101 wrote:
Mon May 20, 2019 6:50 am
dl324 wrote:
Mon May 20, 2019 12:36 am
Wrong answer. Nothing would happen because there wouldn't be a complete circuit.
Depends what else is connected and how. I wouldn't rely on "Nothing", but "fry" is not certain.
scotty101 wrote:
Mon May 20, 2019 6:50 am
In this case the COM pin should be used as ground
+1
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ankith26
Posts: 101
Joined: Mon Mar 25, 2019 11:08 am
Location: Earth
Contact: Website

### Re: Down convert +24DC to 5V

I would suggest getting something like thishttps://www.amazon.co.uk/Adapter-Conver ... way&sr=8-4
Connect +24 VDC to red wire and COM to black wire.