Hi, I assembled indicator beacon using led, ne555 and cd4017. It is propelled by 12V from a cigarette socket in a car. ICs sometimes get damaged, when beacon is plugged during engine start. I assume that problem is either spikes or reverse voltage. How to build simple protection ?

 

There's lots of information on www, for instance:
https://www.st.com/content/ccc/reso...df/jcr:content/translations/en.CD00181783.pdf

 

Hi, I assembled indicator beacon using led, ne555 and cd4017. It is propelled by 12V from a cigarette socket in a car. ICs sometimes get damaged, when beacon is plugged during engine start. I assume that problem is either spikes or reverse voltage. How to build simple protection ?

Gone are the days when I added all sorts of electronics to vehicles I owned – but that was in the days of no lights on reminder, no intermittent wipers, no alarm, no electronic ignition system etc.

Most of the time I would protect the added circuit feeding the +12V through a diode with a large electrolytic capacitor providing smoothing and minimising the voltage drop in the circuit, while engine cranking.

 

Load dump big problem in Vehicles -

https://www.planetanalog.com/author.asp?section_id=3294&doc_id=563761

https://en.wikipedia.org/wiki/Load_dump

https://electronics.stackexchange.c...-do-i-protect-against-an-automotive-load-dump

https://www.infineon.com/dgdl/an-1058.pdf?fileId=5546d462533600a401535591d9860fc5

https://www.nxp.com/docs/en/application-note/AN5082.pdf


Regards, Dana.

 

Load dump big problem in Vehicles -

https://www.planetanalog.com/author.asp?section_id=3294&doc_id=563761

https://en.wikipedia.org/wiki/Load_dump

https://electronics.stackexchange.c...-do-i-protect-against-an-automotive-load-dump

https://www.infineon.com/dgdl/an-1058.pdf?fileId=5546d462533600a401535591d9860fc5

https://www.nxp.com/docs/en/application-note/AN5082.pdf


Regards, Dana.

But that only happens when you disconnect the battery.

 

https://www.mouser.com/applications/automotive-circuit-protection/

Load dump power surges are unique to automotive applications. Load dump pulses are momentary voltage spikes on the car’s 12V power bus caused by the rather slow regulation of the alternator output voltage. The sudden removal of a large load on the power bus (such as a disconnected battery, a blown power fuse, etc.) will cause the alternator output to suddenly jump to 60 volts or more. It can take as long as 400 milliseconds for the voltage to recover to normal tolerances.

Regards, Dana.

 

Other techniques include using parts rated at higher than usual voltages, such as regulators that can handle large spikes and varistors across the power supply. TVS diodes are probably a more modern solution.

 

See

 

https://www.mouser.com/applications/automotive-circuit-protection/



Regards, Dana.

Since he states it is happening during starts, I'd add the starter motor turning on and off to the possibility of a "load dump".

 

Many ICs will die if the voltage on certain pins exceeds that of the supply.

Engine cranking may result in a sudden drop in the supply voltage to the IC, but other IC pins may be held up by charged capacitors within the circuit – destroying the IC.

 

For example: when using LM317, a diode is added to avoid damage to the chip.

 

I've just added ceramic capacitor and diode, hope it'll help.