Bistable relays

Phil,

The coils of the relays are electromagnets. Perhaps the field from the adjacent relay is influencing it.

Noel

Sounds like the magnetic field from the adjacent relay is affecting the operation of the relay. Move them further apart or build a magnetic sheild between the relays or buy pre-shielded relays.

Rob

Is it possible that it is a contact problem - e.g. using non-gold contacts for signal switching with negligible current flow can lead to unreliability as there is no 'wetting' current to break through oxide layers

Thanks Rob, but the relay breaks contact when static, just tapping the relay unlatches it so that the common is not connected to either the NO or NC.

Phil

What is the shock rating of these relays ? The relays I am currently using has a shock rating of 20g and a vibration rating of 12g.

Regards Anton Erasmus

I've got a product with several bistable relays mounted next to one another (with maybe a 0.05" gap), with no problems.

The only problem I've seen would be caused by a sharp impact, like dropping the PCB from several feet, onto a concrete floor.

We had a relay contact to fail a couple of years ago (but not on this product). My customer scanned the contact with an electron microscope, then did a spectro analysis of the contact material. Turns out there was cleaning fluid on the contact (this is a sealed relay), and I had to replace all of the relays with that batch number. The point is, my customers are pretty picky about stuff like this, and I'm sure I would be aware of any problems.

-Hershel Roberson

Rated at >100g (destruction) other than that no other data, I have found that as Noel & Rob pointed out that close proximity of the coils does cause a problem. But my main concern is that the relays do have this third state where the common is not connected to either the NO or NC contact and can be induced by mild tapping.

Phil

A shot in the dark: broken spring?

A bad spring and a broken rivet are the most common failures of relays if the contacts are not obviously burned.

Take apart one of the relays, is there a small permanent magnet inside as an "assist" to the coil?

The suggestion that the spring is faulty is valid, also that the mechanical pivot is somehow at fault comes to mind. Also a mistake during the construction is possible.

I haven't seen mention of the manufacturer's name, perhaps it is time to do so and also get on the phone with their engineers and provide them samples to test in their facility.

Rob

I purposely did not mention the manufacturer until I know for sure what the problem is. I think that it would be unfair to give someone a bad name unless it is proved to be faulty. I will send the manufacturer samples and the details of what I have found and try to get an answer.

Phil

Before you do that, you might want to remove adjacent magentic field relays, and try one in isolation - just in case....

There are different relay designs - does your's have a spring, or does it drive the armature between two magnetically stable states ?

-jg

The problem is that I have a state there is no connection with the NO or the NC and that a slight tap of the relay induces this condition. The adjacent magnetic field is seperate to this, so even with one relay the problem seems to exist.

I have no idea if its spring or armature driven, maybe later I will take one apart and take a look.

Phil

Talk to the manufacturer. They may have some suggestions. My suggestion is to look for another model.

Thad

Recently the turn signals on my car failed and I traced the problem to a relay. Because I lacked a handy replacement part, I took apart the defective relay and found cracked solder joints where each of the spade connectors attached to the internal PCB. It's a long shot, but your problem reminded me of this, so it might be something to look for.

Ed