Relay Coil has Polarity?

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ThomsCircuit

Well-Known Member
Part# NA12W-K
Datasheet= Taydel Electronics
Why does this have a polarity? I like it because its small and this version is a SPDT. I use it to trigger a larger relay coil and illuminate an LED as shown in this schematic.
Im concerned because the datasheet has no mention of it.
 

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ThomsCircuit said:
Why does this have a polarity? I like it because its small and this version is a SPDT. I use it to trigger a larger relay coil and illuminate an LED as shown in this schematic.
Im concerned because the datasheet has no mention of it.
Click to expand...

Some relays have a diode built-in across the coil, in which case it MUST be wired the correct way. I suspect the PCB is designed to optionally use that kind of relay.
 
ThomsCircuit said:
Why does this have a polarity?
Click to expand...

Do you mean the voltages shown in the data sheet as, "must operate" or "must release"? If so those are just the voltages that are used to meet the standards, meaning they won't work in a circuit that uses a negative voltage.

Noe some car relays are polarity dependent on the coils. They have a built in diode to protect the rest of the circuit when shutting off. But these don't seem to have that in them.

Looks like I type too slow.
 

The datasheet schematic diagram has polarity markings because it is intended to represent both a standard relay coil (that isn't polarity sensitive) and a single coil latching relay (that IS polarity sensitive). The part number you've supplied is a standard 12VDC relay.
 
eTech said:
The part number you've supplied is a standard 12VDC relay.
Click to expand...
i see now that the data sheet represents ALL of the series for this relay. I do however have 3 of NA12WK and these are polarity sensitive. At the bottom of the document (pinout area) it "shows" both NA and NAL (latching) are both polarity sensitive. Awesome information. thank you.
 
I zipped through the datasheet, and did not see any mention of a suppression diode option. However, there are two different latching versions, and those are polarity sensitive. The bottom of the relay has markings molded in for all variations; the + and - markings do not apply to the non-latching versions.

ak
 

The NA12WK IS NOT polarity sensitive. Only the latching type relays (NAL) of this NA series are polarity sensitive.

BTW- The datasheet does not indicate that any of these relays are available with a diode.
 
I'd suggest following the polarity in the data sheet, even if you don't have a latching unit. I've been stung by such a relay in the past. I don't recall the model, it was a simple SPST unit but it was polarity sensitive and would not work at all with polarity reversed.
 

Non-latching and polarity-sensitive probably means it had an internal suppression diode.

ak
 
AnalogKid said:
Non-latching and polarity-sensitive probably means it had an internal suppression diode.
Click to expand...
This was 25 years ago and the result of my naivety. Hopefully the TS learns from my mistake and doesn't fab a board with the relay miswired. That's what I did. Fortunately it was a prototype and was corrected before we went into production.
 
Lo_volt said:
I'd suggest following the polarity in the data sheet, even if you don't have a latching unit. I've been stung by such a relay in the past.
Click to expand...
A good idea.

Some low power non-latching relays use a permanent magnet "assist" to reduce the operating power, which means the coil polarity must be correct to interact with that.
 
Probably not the case here, but some relays have an LED to show that they are activated. That LED may only work one way even if the relay doesn't mind.

One 12 V plug-in relay that I used had an LED that was actually two LEDs in parallel, in opposite polarities, to get over that issue.
 
eTech said:
The NA12WK IS NOT polarity sensitive.
Click to expand...
This is why i created this post. I was thinking the datasheet is wrong or ive got faulty parts. But i will confirm that when i hook this up to 12V it will not trigger the coil unless i have the positive lead connected to pin one.
 
eTech said:
I suggest testing the relay and not assume anything...
Click to expand...
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.
 
MaxHeadRoom78 said:
So all you need is a latch pulse to retain and a unlatch pulse of opposite polarity to release.
Click to expand...
Im a bit new to this but Im finding a good deal of incorrect information (pinouts, voltage, polarity) on some parts. For example in "design spark" the polarity of a PCB image on an LED was reversed. And I kinda dont trust anything but thats just me.
 
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