This circuit is a must have
This is a low budget timing light for testing on the bench or on the car.
- very few components
- very cheap
- extremely useful: you can reveal
- trigger related problems
- bad configuration
- potential firmware problem
Don't start to crank your car before you've seen these LEDs flickering nicely on your table-setup.
This might look too simple, but as cases like MembersPage/VdBVolvo shows professional feature-creep lights can trick you (offsetting the time of the output flash with the wrong crankangle!), so light that flashes at the time of the spark definitely has its advantages (timing-guns also exist - often with the convenient inductive clip - that flash at the time of spark, and the featurecreep timing-gun most likely has a setting where it will flash at sparktime without applying bad offset-angle).
Schematic:
Note that the diode needs to be at least 500V (1n4007 is 1000V, and a bit slow, BY399 might be a better choice) if you are using this when the coil is there on the IGBT output (the coil makes high voltage intentionally utilizing flyback technique). No need for the 1n4007 diode when trying without the ignition coil (transformer to be precise), but it doesn't hurt.
A different version, that only lits when ignition transformer (not logic-level input transformer!) is actually connected - is available in WebShop under [5mm LED]. Small, cheap, but very strong light. Mostly useful to adjust trigger_tooth and ign_tdcdelay with commands mda01 ..mda28 (forced ignadv 0.25 .. 10 crankdegrees BTDC).
what are the limits of light amplitude?
- you can use 3..4 red LEDs in series with 27..47 Ohm pullup to 12V sounds good.
- 2..3..more of these can be connected in parallel if you want it brighter
max current for LEDs: a 5mm red LED can take up to 200..300mA, (some say 1A) with low-duty (infrared LEDs in remote controls are really driven close to 1A with short spikey).
MembersPage/Fero 's long cranking problem (with an old experimental firmware and special config a bit too many cranking revolutions were needed to get in sync):
with such LEDs we immediately revealed the problem.
See also