J
Jordan
Guest
Some weeks ago I asked for help with a car blinker circuit, that was
prone to being affected by the (magneto) ignition system.
I think I've found the cause - the 555 IC itself.
I've only checked it on a bench so far, using a spark generator to
simulate the unsuppressed high tension ignition spark.
After breadboarding the circuit for the umpteenth time, I used a
different brand of 555 - a National Semiconductor. I'd previously used
KIA brand, thinking they'd all behave the same. Not the case - the NS
555 doesn't behave erratically with the spark nearby, whereas the KIA
555 always does.
No filtering was used either, just a cap on pin 5.
Lesson learnt!
Here's hoping it'll work OK on the vehicle now.
Many thanks to all who suggested fixes.
Jordan
prone to being affected by the (magneto) ignition system.
I think I've found the cause - the 555 IC itself.
I've only checked it on a bench so far, using a spark generator to
simulate the unsuppressed high tension ignition spark.
After breadboarding the circuit for the umpteenth time, I used a
different brand of 555 - a National Semiconductor. I'd previously used
KIA brand, thinking they'd all behave the same. Not the case - the NS
555 doesn't behave erratically with the spark nearby, whereas the KIA
555 always does.
No filtering was used either, just a cap on pin 5.
Lesson learnt!
Here's hoping it'll work OK on the vehicle now.
Many thanks to all who suggested fixes.
Jordan