Thread: A little help needed understanding relays

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Hello all,

First of all, I would like to say that this forum is just great. I've only recently discovered it, but it's amazing the information that is present! Thanks to all the contributors.

I would like, if I may, to take advantage of your expertise concerning relays - specifically, I believe, SSR ( solid state relays ) if that is what the below is, or simply a relay that goes onto a PCB. In looks, it's a very small black plastic box about 3/4" by 1/2" with 5 pins on the bottom.

I've not used relays before for props, but have had the opportunity to acquire the one's shown below and am ready to experiment. The issues I'm currently having is reading the actual relay. I understand, I think, that the coil is 12 VDC and that the relay is a SPDT type, but what I'm having trouble understanding is the rest of the amps and voltage ratings, since, to my newbie eyes, it seems there are two sets of ratings -one on the right side, and one on the left. I've tried to look up the model of the relay, but the manufacturing site does not list it.

I apologize, as I can't get a picture of the relay to focus in enough to show it non-blurry, but here's the info I have:

Make: Ston
Model: S3-12

Printing on left side:
50/60Hz
12A/24VDC ( followed by a straight line with three dots below it )
12A/240VAC ( follow by a ~ line)

On the right side is:
10A/24VDC
7A/240VAC
Coil: 12VDC

So what I'm trying to learn is what voltage I can use for loads on this relay. It seems to be 24VDC or? 240VAC - does that mean one can also use, say, 120VAC or not?

Thanks for anyone who cares to throw an answer my way - I know it's difficult when you can't see the item, but I hope the above info gives someone with some experience a clue.

Thank you again!

I can't speak for your specific relay but in general the basic relay has three main components

1 the coil, this opens and closes the relay, on yours it looks like its energized by 12VDC current so don't apply any other current or it will not work or you could burn up the coil which it again will not work.

2. The second part are the contacts these are what turn on or off the power to the device you are controlling. There are several types Double Pole Single throw, Single pole single throw, Double pole double throw, etc, this has to do with the number of contacts. Don't know what you have These are rated at the amount of current voltatage they will handle.

3. You need to know if the contacts are NC Normally closed or NO normally open this will determine when the power is flowing, So if it NO and the coil is not energized there is no power flowing across the contacts to the device you are controling. when you energize the coil the contacts close and the power flows across the contact to the device. NC means the contact are closed all the time.

I suggest that you do a search on your specific relay and try and find the diagram this will give you the details you need to connect it properly. Best of luck

Based on what you have listed you can really run any voltage you want on the contacts..... whats important is the 'A' (max amperage rating) that the contacts are rated for. Voltage wise you can run (based on the info you supplied) anything up to 240vac. Just dont go beyond the amperage rating for the contacts?

Thank you both - that really helps out - I was mainly concerned about the potential of running 120VAC through the load since it's not, technically, listed, but logically, it seemed alright if you can do 240VAC.

Thanks again!