Circuit protection device ??

[peter-f]

I've been poking into some DC power supplies - used for model trains - 15VDC, 18VAC, 10VA max. (this example is 1 year old- another is similar and 10+ years old with different part #)
These have an overload protection device that I do not recognize...
2 leads into a glass tube about the size of a Neon bulb.. but a bit longer (1 inch oveall, 1/4 inch dia)
Each connects to what appear to be a relay contact - when a short is detected, this apparently opens until it cools.
Simple, but not very apparent in operation (power's out, must be a short - not very informative).
The question of the hour is simple... what is it?
(Number on outside of glass reads
3S8701A 3K -or-
ESB701A 3K - or some such - no use looking via Google- no useful result found)<p>Any clues?

[Enzo]

It is a circuit breaker. Self resetting. It heats up and breaks, then after some period of time it cools down and resets. The numbers may be house numbers rather than industry numbers.<p>Have you contacted the maker for information?<p>You can probably make a good estimate of its rating by looking at the spec for the unit it serves.<p>Yours is a bimetal mechanical switch, but you might also consider using a polyswitch. Those are PTC devices that act like fuses.

[Chris Smith]

Most electronic supplies have different versions of the same thing, in little square boxes.

[peter-f]

Thanks for the response- I just don't know which catalog may carry such a device (none found in Mouser... or it's hiding on a corner of a page that I didn't see yet.)<p>And these Mfr's are so small they'd share Nothing! (I Don't blame 'em)<p>My father made a similar power supply (circa 1960) with a breaker that caused a buzzing sound-- seems it has a similar bimetal device with the glass case broken to cool rapidly - thus create a cricket-like chirping when overheated. Can this be right?

[Chris Smith]

Sounds about right.<p>Try Digi Key, and maybe all electronic for the larger type CBs. <p>I have used Turn signal canisters for Circuit breakers, and even some times standard CBs buzz as the "make and break" happens too fast. <p>Usually worn out ones will buzz instead of heat up properly.

[jollyrgr]

If you need higher current versions you can find these at auto parts stores and places that sell automotive electronic parts. The high current versions are in metal cases.

[peter-f]

Chris-
thanks
My dad's version gives that reassuring (?) audible signal that something's wrong.<p>And I'd never have considered a turn signal-- what a concept!

[terri]

Try checking the Clixon company. Their name is almost synomymous with "circuit breaker," like Kleenex is to tissues.<p>The make a load of overload (thermal and electrical) protection devices as for example, motor reset buttons on your garbage disposal, overload switches on your 'fridge and room air conditioners, etc. I've got an automotive battery charger with one of their breakers in it.

[Enzo]

You can use most any circuit breaker of suitable rating, it doesn't have to look the same.