Anyone tell me what this does

[Quantised]

Does anyone have an idea how this works.
It flashes the LED but also loads the supply with some nasty spikes
The zener is not known as it is buried a bit in the circuit and I dont want to destroy it - just in case.
Can I just use the resistor and the LED and forget the rest.

Why does it cause such a spike as the supply wires are 10AWG.
Thanks

https://www.electro-tech-online.com/attachments/capture-jpg.26523/

 

[Nigel Goodwin]

I would have thought using just the LED, and a correct value resistor, would be perfectly fine.

 

[Quantised]

Thats what I thought but why does it give such spikes down the 12v DC line.

It upsets some electronics connected on the same power supply line but why?

Thanks in advance

 

[killivolt]

Whats your 12v source. Maybe your supply is corrupt and then your inductors are un-stable. If it's a battery probably not.


Then check your resistor is it metal oxide or carbon film.


kv

 

[RadioRon]

I suspect that it is not a zener but some sort of negative resistance diode, like a tunnel diode. If so, then it naturally would cause oscillation and thus flashing of the LED. Perhaps those coiled wires are inductors to slow down the oscillation? Just a guess, and even I'm skeptical because most tunnel diode circuits are for higher frequencies. There are quite a few tunnel diode circuits shown, including relatively slow multivibrator circuits that look a lot like this, in "GE Transistor Manual" 1969, General Electric, edited by J.F. Cleary. chapter 14.

 

[Quantised]

killivolt - The LED circuit is on a starter circuit for a generator, it has wiring directly from a 500AHr battery which supplies voltage to the glowplugs about 15A each and then pulls the solonoid in to start the engine. So there is plenty of power on the supply. Oh and I think its a carbon film.

RadioRon. I was intrigued and so eventually had to dismantle the control panel and get the components out. The resistor was actually a 33R value (measured) and the zener is an IN4739A606 which seems to be a 9.1volt item. Maybe the 33R is low enough to allow it to cause the 2 volt ripple?

What I think happens is the that when the engine is being started the volts drop to around 7 due to the high start currents (so no light on) and then when the engine starts the voltage raises back to about 12v and the light then flashes to indicate it is running. The strangest thing as I know its running as it makes a loud growling noise - why I need a light is not clear.

Anyway I have ripped it all out and will put a suitable resistor in just so the LED is on, always essential to have lots of LEDs.

Thanks

 

[RadioRon]

Well, so much for my exotic diode theory. It is obvious that this particular LED is one of those types that has built-in flasher switching. Most common LEDs don't and would not flash but just stay on steady.