What type of component is this

A 'spark gap' perhaps.

Typically incorporated as an ESD protection device, in this case, I suspect it is being incorporated to keep EMP (as it were) from causing pre-mature circuit failure modes.

So, it is probably a pretty low voltage device tied between the main rail and ground ring of the PCB, and might just fire every time the fence does, and quells that induced EMP spike from causing 'infant mortality' of an otherwise fine design.

It may be a kludge, or that may well be the way they do it in that niche of the industry.

This is just a guess, mind you.

a diac?

-Lasse

Lightning arresters are a necessity for electric fence controllers, they usually have several, probably a spark gap type like so:

Can you post a picture somewhere? That will improve the guess a bit.

tm

That would be my guess, assuming the controller has another transformer in addition to the output transformer.

Best regards, Spehro Pefhany

Aren't those usually marked with something like Zed (a Z with a bar thru it)? ...Jim Thompson

Um, nice. But who carries them for hobbyists?

Googling, +meritek +msa1, doesn't come up with much. Octopart, also comes up short.

Jon

le

If he's a hobbyist, he's outta luck. A pro could contact the manufacturer of the controllers.

That sounds like a Sidac (sp?), which I've seen in gas ignition modules.

I've seen diacs exactly as the OP described, in fact here's a photo of a Panasonic one:

Best regards, Spehro Pefhany

ddle

=A0 =A0...Jim Thompson

"The Journey is the reward"

eff.com- Hide quoted text -

Okay- a DIAC makes sense for triggering an SCR discharge of a big cap into the output HV transformer. Goes to show context does help the situation...

Why?

When the place I worked made them our biggest worry was the package, it had to withstand being run over by a tractor, hidden in the grass. The fencer units operated from a 12V car battery, so lightning would only hit the HV side of the output transformer. Considering one was dumping 5kV pulses onto the fence, lightning was the last thing we were worried about.

An important thing was making sure the pulses were far enough apart so a sheep's brain had time to 'reboot' before the next pulse, wouldn't want the farmer seeing a line of starving sheep stuck to the fence. Sheep are not very bright, 80 pulses per minute and their brains lock up.

Grant.

This has got to be the funniest think I've seen in ages. Every time I read it I laugh almost uncontrollably.

Thanks for that.

John

le

From what I'm reading, lightning is the single most frequent cause of electric fence controller failure. The surge is not from the mains so much as the fence itself. The lightning does not have to strike the fence, only strike near enough to induce a damaging voltage. The same protection schemes apply to line operated the same as solar/battery powered installations. From your description of battery operation, controller in the grass, sheep etc...you must be talking about the moveable fence types to prevent overgrazing by sheep- typically smaller than a permanent pasture fence.

Correct. They were portable units for just that use.

Grant.

Very many thanks to everyone. I've forwarded comments and links to my friend.

David Eather