# 12V USB Relays



## Broshi (Jun 9, 2012)

Not sure if any of you are using them, but I picked up a Sainsmart 8ch 12V relay board for the CarPC. It seems to be working fine, but it refuses to put out any voltage when the relay is switched on. What exactly could be going on? I've done a ton of troubleshooting but to no avail. Ideas? Here's a picture for reference.


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## Ultimateherts (Nov 13, 2006)

Output wires reversed (Positive in negative; Negative in Positive)? Software? Any dip switches on it? I am just generalizing as I have never used one!


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## Broshi (Jun 9, 2012)

Ultimateherts said:


> Output wires reversed (Positive in negative; Negative in Positive)? Software? Any dip switches on it? I am just generalizing as I have never used one!


Possibly. I can't seem to figure out which output is which. There is absolutely no documentation on these things. Not even a GND/5v/12v labeling on the relays. I've tried testing for voltage but absolutely nothing seems to read except for the voltage input on the board which is a solid 12. 

The lights flick on and off when I use the software for it. No dip switches surprisingly and unfortunately. For $23, this thing is awesome! Well... If I could get it to work of course.


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## ATOMICTECH62 (Jan 24, 2009)

Now,take into consideration I have no idea what this thing is used for and I have never seen one before.Here goes.
Since you say the relays click but there is no voltage and there are 3 terminals for each relay(apparently).I would guess that each relay has one terminal for input voltage and the other two switched.One normally open,one normally closed.
Single pole/double throw.(SPDT)

Im also going to take a shot in the dark and say the center terminal would be the common for the voltage input and it would throw on ether side of it.
Since each relay is independent from the other you could send a different voltage to each one and not be stuck with a common rail voltage for all.
5volt on 2,9volt on2,12volt on 2,24volt on 2.Or whatever.

A picture of the bottom of the board might help if the traces are visible.
But.
If you have already tried this then please disregard this post?LOL.


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## Broshi (Jun 9, 2012)

ATOMICTECH62 said:


> Now,take into consideration I have no idea what this thing is used for and I have never seen one before.Here goes.
> Since you say the relays click but there is no voltage and there are 3 terminals for each relay(apparently).I would guess that each relay has one terminal for input voltage and the other two switched.One normally open,one normally closed.
> Single pole/double throw.(SPDT)
> 
> ...


I found out why it wasn't working with a little more searching and the help of both of your posts. Turns out I'm an idiot haha. Applied 12v to the common and the positive of the test LED to one of the remaining terminals. It works. Idiot me thought that one served as a ground while 12v was applied via the board voltage input. Meh. Works now! 

For those of you that haven't used one of these before.... Get one. $28 USD and worth every penny. I very well plan on using this to control latches, windows, sunroof, air ride (possibly), HVAC as well as a few other things.


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## Thumper26 (Sep 23, 2005)

Broshi, what are you using to interface with all of those? Just getting a carpc together myself.


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## Broshi (Jun 9, 2012)

Thumper26 said:


> Broshi, what are you using to interface with all of those? Just getting a carpc together myself.


The relay board has a simple GUI that you can download for the specific model. If you're asking about what I plan on controlling with these, see the above.  These things are awesome. :surprised:


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