Relay Coil has Polarity?

Follow the indicated polarity, and you won't go wrong. In many cases, the relay may possibly include a diode, and when you order one, you might get that version. If you follow the markings, it won't make any difference.

I recently learned that automotive relays come in a common package, but some relays in that package include a diode and others do not, which is not necessarily marked on the package. Follow the convention and it doesn't matter.

ThomsCircuit said:

Thats what I did. Despite what the datasheet says the coil is polarity sensitive. I did a lot of searching before i created the post and I could not confirm (on paper) that this NA12w was polarity sensitive but here we are. View attachment 132090

Click to expand...

Good deal....you tested and removed all doubt.

ThomsCircuit said:

Snip... I kinda dont trust anything but thats just me.

Click to expand...

Sounds wise to me

Sometimes it's not the relay that has the diode, but the socket: https://ceautoelectricsupply.com/product/5-wire-relay-socket-with-diode-protection/

The automotive relay https://www.12voltplanet.co.uk/relay-guide.html


In today's world, there is a lot of "don't care" stuff going on, but "sometimes it matters.

In the automotive relay, we have the diode problem, the polarity markings that most ignore, the diode in the socket instead of the relay and the terminal numbers being different.

What's a little disagreement between friends?

I do remember when I was in an explorer's post at HP, I was asked what color wire (black, white_ would have the fuse and switch?
I said black and the guy teaching us was wrong. This was a US 120V black, white, green system of colors.

An AT&T telephone repair person who said he taught how to repair the telephone lines. I asked him why handset to station lines are reversed. He said it didn't matter. I finally came up with a good reason: It keeps TIP and RING the same colors except through the wall cord. Patch cords would be straight-thru.

The word of thermocouples threw me. red, most of the time is negative.

Sorry, screenshot doesn' t work right.

Lo_volt said:

learns from my mistake and doesn't fab a board with the relay miswired.

Click to expand...

I almost did.

Many high sensitivity relays use a internal polarizing magnet. So coil drive polarity is important.


Polarized Relays
Polarized relays use the magnetic flux of the permanent magnet in their electromagnetic sections. This means that the operating coil has polarity.

Don't mean to best this to death but....

If your circuit doesn't require a polarity sensitive relay, then for part interchangeability reasons, its better not to use one.

eTech said:

its better not to use one.

Click to expand...

And throw away $5.50?
I certainly wasn't planning on it but I have 6 and its not a problem. If I were selling stuff I'd probably not use these.

nsaspook said:

Polarized relays use the magnetic flux

Click to expand...

Thanks. All the info is much appreciated.