[Diy_efi] Re:555 Timers

[Geoff Harrison]

Tried an idea for getting timing pulses for timer controlled EFI today.
Used a ferrite toroidal core with 23 turns of 16 AWG wire out of the junk 
box.
The B+ lead to the ign coil passed through the core once. The pulse I got
looks good. 200mV with fast rise time, falling exponentially back to zero
with slight ringing. The rise is due to the coil being energised, the 
ringing I suspect
as the plug fires. The core has an OD of 1", ID 1/2" and 1/2" thick. Its 
original
line of duty was AC mains filtering, so its only a low frequency type, and 
should be
available from Tandy/Radio Shack and similar outlets.
Remember the pulse occurs way BTDC, when the points close, not open. It has 
no
loading effect on ign circuits, or electronic tachos when fitted. I doubt 
that the series
inductance would have an effect on Ign, its probably less than the wiring 
back to battery.
If a bigger pulse is required, just increase the turns, i.e. 10mV per turn.
If the pulse is going the wrong way, just reverse the connections.
BTW, the test vehicle was wife's Suzuki 1300. She's worried I had it hooked 
up
to the cro. I told her it needed defribulating.


Geoff Harrison IT Services.
Port Macquarie  NSW.
Tel 65827181
Mob 0401324639 
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