# Relay Pins Identify

Joined Sep 28, 2021
266

Hi, do the green highlighted pin to connect the main voltage and is the blue one the input switching voltage on the relay? Since there are another 2 pins near the blue highlighted pin, I assume we can connect to either pair right?

#### Tonyr1084

Joined Sep 24, 2015
7,562
The two GREEN pins are the "C" or "Common" pin. The two BLUE pins - one of them is the "NC" or "Normally Closed" pin and the other is the "NO" or "Normally Open" pin. Switching occurs between C and NC or C and NO, depending on how you want the switch to function. The two pins (not colored) are the control coil pins. That's where you apply the voltage to trigger the switching action.

Here is the data sheet I found. Yours is the 12VDC model as is indicated by the nomenclature chart.

#### Ian0

Joined Aug 7, 2020
8,954
Measure the resistance between them. If they are either open or short then they are probably the switching contacts. If you get a few hundred ohms, you have found the coil pins.

#### Tonyr1084

Joined Sep 24, 2015
7,562
The two inner most pins are the coil while the two pins closest to the coil pins are the NO and NC pins. Which is which? A continuity check will reveal which is the NC. Then one can infer which is the NO, because it will be normally open.

Joined Jan 15, 2015
7,256
Just look at post #2 which includes the drawing. It also includes the .pdf data sheet.

Ron

#### ThePanMan

Joined Mar 13, 2020
707
Measure the resistance between them. If they are either open or short then they are probably the switching contacts. If you get a few hundred ohms, you have found the coil pins.
I would have to disagree. An open reading between the NO and C pins indicate a part of the switch. However, if you measure between the NO and NC pins you're going to always get an open because they, though part of the switch, are contacts that are never in common, except in common with the C pin(s). Only the coil leads will show some measurable resistance. It's important to identify which pin(s) is the Common.

#### Ian0

Joined Aug 7, 2020
8,954
I would have to disagree. An open reading between the NO and C pins indicate a part of the switch. However, if you measure between the NO and NC pins you're going to always get an open because they, though part of the switch, are contacts that are never in common, except in common with the C pin(s). Only the coil leads will show some measurable resistance. It's important to identify which pin(s) is the Common.
Maybe I underestimate the amount of common sense that has been applied.
If they are either open or short then they are probably the switching contacts. If you get a few hundred ohms, you have found the coil pins.
So just to clarify, if you find the coil pins then they are not the contacts.
Common, normally-open and normally-closed are ALL switching contacts. If you have a multiple pole relay, then you may have to power Up the coil to find out which contacts close and which open.

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#### Tonyr1084

Joined Sep 24, 2015
7,562
I think what ThePanMan is saying is that there's going to be an Open between NC and NO because those never close. One could conceivably think that the NC contact is the C contact. Unless one switches the relay on one would never be sure.

OK, I've seen the diagram too. In this case we know which is C. The diagram makes that clear. Holding the relay in the same orientation SHOULD tell you which is the NC and NO contacts. But "Common Sense" is merely the level of sensibility that is common among your contemporaries. If you hang around with people of no common sense then you probably don't have it either. I'm not labeling anyone as lacking good sense, I'm just saying that not everybody knows how to solve problems as well as others. When I was young I had the same level of sensibility as those I hung around. We got called ass holes often enough, and looking back - we were. Again, not labeling anyone an ass hole, just saying that maybe the TS might not realize the chances of mixing the C and NC pins. In its de-energized state there will be continuity between both C pins as well as between either of them and NC. It COULD confuse someone.

#### ThePanMan

Joined Mar 13, 2020
707