Pulsing Third Brake LIght Problem. ( whats wrong with this cct ? )

Hi i make this cct. And its working as usually ( some blinks and then continuously on ) when i connected it to my PSU ( 12V ).

And then i connect it to my car it doesn't give me any damn blinks. ( its happend only when engine starts )

My car voltage is 13.8 - 14V

Whats wrong with this cct ?

What r the changes that i have to do ?


Plz help me coz im sick with this cct

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This is the link for main site
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Thank you very much

Car alternators produce high voltage spikes. So I expect that these are affecting your circuit. It is a wonder why they have not damaged the IC.

I suggest that you connect a 1 k resistor in series with the +12 Volt line to the left of R9 and a 9V1 Zener diode from the other end to gnd.

So R9 and Q2 remain connected to the +12 Volt, but the rest of the circuit is supplied from the 9.1 Volt line.

I also suggest that you connect a 220 uF elecrolytic capacitor and a 100 nF ceramic cap in parallel with the Zener.

These will regulate the supply to the IC and suppress the spikes.

It is working fine on my motorcycle, but i will make the suggested changes for properly long-term operation.

The entire circuit is supposed to receive its power from the brake light switch. +12V is not supposed to be connected continuously to any point in the circuit. **broken link removed** explains this.

Now its working perfectly.

I connect directly Emitter and Base through 47K resister. Then its work normally.