You can't add resistance to the circuit and make an led light up from a
spark. The led needs a certain amount of current at around 1 volt.
There is not that much current in the spark. The coil trades currrent
for voltage when it steps the voltage up to that many volts. You would
need to build a trigger circuit tha detects the spark and the powers
the led.

basskisser wrote:
news.wildblue.net wrote:
that's about the firing voltage of a spark plug.

Yes, it is, but that doesn't mean the LED has to handle that 50,000
volts. Think resistance.....