Message text written by George Richardson
>Sorry Randal, but power is used to drive the ICs in the unit as well as
supply voltage to the base of the transistor that turns on the coil. The
ICs, if they're anything like those in the Piranha ignition system,
require a minimum of 5 volts to operate. And although it may not make
any difference in the majority of cases where the connection is made, in
the case of a coil and resistor that are not matched, there could be a
problem supplying adequate voltage.
In this case, the coil measures 1.1 ohm and the resistor measures 1.7
ohms so:
( 12 volts/2.8 ohms)*1.1 ohms = 4.714 volts across the coil when the
ignition is on, not accounting for the voltage drop of the switching
transistor.
By the way, I designed my first electronic ignition more than 25 years
ago.
<
And this ignores the effects of the supply voltage transients everytime the
switch turns on and off. This can cause false triggering and erratic
firing.
Dave Massey
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