Help on how to read this relay pinout

Thread Starter

EricSutton

Joined Oct 7, 2018
37
Hi, I am trying to use this relay: KEMET_EC2-12TNU
On the datasheet it shows this:
Relay.png
I understand pins 1, 6, 7, and 12 are for the setting and resetting of the relay.
Pins 3, 5, 8 and 10 are the connections, but what about 4 and 9?

The double coil latching relay is what I am using.

Any help is appreciated.

Thanks!
 

ebp

Joined Feb 8, 2018
2,332
In the RESET position (the coil between pins 5 and 6 is the one most recently activated) Pin 2 connects to pin 4, pin 10 to pin 9 and pins 5 and 8 are open. In the SET position, pin 4 would connect to 5, 9 to 9 and pins 3 and 10 would be open. Pins 9 and 10 are the "moving" contacts - attached to the armature of the relay and actually physically moved by the operation of the coils. It's a bit of an odd way to draw them. In a non-latching relay, the other pins would be for the "normally open" (N.O. or NO) and "normally closed" (N.C. or NC) contacts, but there really isn't such a thing as normally open or closed for a latching (sometimes called "bistable") relay.

Note this is a bottom view diagram and that the coils are polarized - which terminal is positive and which is negative is important. This is because the latching is done with permanent magnets. Lots of small non-latching relays also use permanent magnets to aid the electromagnetic force of the coil so less current is required to operate the relay. Beware! Relay pin diagrams are often bottom view, but not always.

I had no idea Kemet was in the relay business! They are a big name in capacitors.
 

eetech00

Joined Jun 8, 2013
2,041
Hi

In the graphic symbol, 4 and 9 are pins each connected to a pivoting contact that is common to both the “set” and “reset” contact pins.

The relay is shown in its “reset” state, so the last coil operated was the reset coil. So common pin 4 is connected to pin 3, and common pin 9 is connected to pin 10.

If the “set” coil is “pulsed”. The contact “pivots” and connects pin 4 to 5, and pin 9 to pin 8, while disconnecting the previously connected pins.

Because its a latching relay, it maintains its state without power.

BTW, the manufacture recommends that the coil be driven by a “pulse” to change state as opposed to energy applied all the time.

Hope that helps.

eT
 

Thread Starter

EricSutton

Joined Oct 7, 2018
37
Hi

In the graphic symbol, 4 and 9 are pins each connected to a pivoting contact that is common to both the “set” and “reset” contact pins.

The relay is shown in its “reset” state, so the last coil operated was the reset coil. So common pin 4 is connected to pin 3, and common pin 9 is connected to pin 10.

If the “set” coil is “pulsed”. The contact “pivots” and connects pin 4 to 5, and pin 9 to pin 8, while disconnecting the previously connected pins.

Because its a latching relay, it maintains its state without power.

BTW, the manufacture recommends that the coil be driven by a “pulse” to change state as opposed to energy applied all the time.

Hope that helps.

eT
Thank you @eetech00 ! That makes everything clear, except one small detail. How do you know that what is shown is the "reset" state? Is that something common to relay datasheets? Always shown is the "reset" state?
 

Thread Starter

EricSutton

Joined Oct 7, 2018
37
In the RESET position (the coil between pins 5 and 6 is the one most recently activated) Pin 2 connects to pin 4, pin 10 to pin 9 and pins 5 and 8 are open. In the SET position, pin 4 would connect to 5, 9 to 9 and pins 3 and 10 would be open. Pins 9 and 10 are the "moving" contacts - attached to the armature of the relay and actually physically moved by the operation of the coils. It's a bit of an odd way to draw them. In a non-latching relay, the other pins would be for the "normally open" (N.O. or NO) and "normally closed" (N.C. or NC) contacts, but there really isn't such a thing as normally open or closed for a latching (sometimes called "bistable") relay.

Note this is a bottom view diagram and that the coils are polarized - which terminal is positive and which is negative is important. This is because the latching is done with permanent magnets. Lots of small non-latching relays also use permanent magnets to aid the electromagnetic force of the coil so less current is required to operate the relay. Beware! Relay pin diagrams are often bottom view, but not always.

I had no idea Kemet was in the relay business! They are a big name in capacitors.
I got confused when you mentioned pins 2 and 4. Also I think you mean pins 4 and 9 are "moving" contacts
 
Last edited:

ebp

Joined Feb 8, 2018
2,332
I got confused when you mentioned pins 2 and 4. I'm guessing you mean internally they are connected and we do not have to worry about them.
I'm sorry! I botched the pin numbers, but I think you have it all straight now anyway. It should have been pin 3, not pin 2.

Regarding "set" and "reset" states - notice that the datasheet says "(Reset position)" just above the diagrams of each of the latching types. I don't think there is any consistency from one manufacturer to another with regard which position is shown.

If you are interested in some good general information on relays, you can find useful applications notes and guidelines for use at Omron, Panasonic (Aromat division, if they still use that name) and TE Connectivity, Potter & Brumfield products section. Relays are actually rather complex critters in some ways. Electronic switching with transistors of various types, SCRs and triacs has replaced relays for many things, but relays are still the "right" thing to use for some applications.
 

Thread Starter

EricSutton

Joined Oct 7, 2018
37
I'm sorry! I botched the pin numbers, but I think you have it all straight now anyway. It should have been pin 3, not pin 2.

Regarding "set" and "reset" states - notice that the datasheet says "(Reset position)" just above the diagrams of each of the latching types. I don't think there is any consistency from one manufacturer to another with regard which position is shown.

If you are interested in some good general information on relays, you can find useful applications notes and guidelines for use at Omron, Panasonic (Aromat division, if they still use that name) and TE Connectivity, Potter & Brumfield products section. Relays are actually rather complex critters in some ways. Electronic switching with transistors of various types, SCRs and triacs has replaced relays for many things, but relays are still the "right" thing to use for some applications.
Awesome, thanks for the tips! I'll check out some of those guidelines.
 
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