simple relay wiring?

I have a simple 5vdc relay I'm trying to figure out how to wire it to the Uno. The three terminals are (S + - ). Am I correct in assuming + goes to 5v & - goes to Gnd ? Also where would S go to?

Just three terminals... Does not sound like a normal relay. Please give us a link to the relay (probably relay board?) you're using.

A relay should have 2 inputs (for the coil), and at least 2 outputs connections. Did you break off one of the leads? LOL
I broke off one of my LED leads last week, and had to trash it!

The S stands for the high/low signal you will send to the relay from the Arduino from one of the pins.

dfoliver:
The S stands for the high/low signal you will send to the relay from the Arduino from one of the pins.

Well, I am still puzzled. If you send a signal from the arduino, you need a ground or something to make a connection. But then you need two or more leads for the output of the relay. So, It still counts up to at least 4 wires as I see it.Unless you have a common ground on one of the relay output pins. Maybe that is how this is hooked up ?

Hi,
The op does not just have a relay, he has a Relay PCB.

It has either an optocoupler or a transistor on it to switch the current to the relay coil.

+5 does go to 5V on the arduino, gnd goes to gnd on the arduino.
S goes to the pin on the arduino you have configured as the output to switch the relay.

Note; some relay PCBs need a HIGH output from the arduino to operate the relay, others need a LOW.
You will be able to work this out when you connect and try to control the PCB.

Tom... :slight_smile:

I know how relays work so I didn't mention the C NO & NC points because I just want to know how the three pins that stick out in the photo link wire to the arduino. You can only see the "S" marked on the last pin but the two you can't see are labled + & -.
Here's the link:

http://www.vetco.net/catalog/images/VUPN5949-2.jpg

You can connect the S pin to any digital port

It's funny because I found the same photo with the light bulb on line before I started this thread. It didn't tell me any more than I already knew from looking at the relay. Whoever made the photo assumes that you already know where the three wires hook up because they just used colors instead of destinations. Something that is obvious to one who knows may not be obvious to one who does not. The bottom photo is a little more enlightening since it shows how the three pins actually hook up. Can I assume from now on that a " + " always goes to the positive input voltage & a "-" goes to Gnd?

leftyg:
Can I assume from now on that a " + " always goes to the positive input voltage & a "-" goes to Gnd?

No, you can't assume anything in this crazy business.

"Can I assume from now on that a " + " always goes to the positive input voltage & a "-" goes to Gnd? "

YES, you can assume that (and be accurate about 99% of the time).

With less accuracy, you can assume the black wire goes to ground, and the red wire is the positive. It is a good idea to test your assumptions with a volt meter before connecting everything together.