Mike H wrote:
> I would like to data log commanded spark events for my vehicle. It
> uses a Distributorless Ignition System which consists of a engine
> control computer, a control module, and a coil pack. The coil pack is
> fed 12v and has control wires. When a control wire is brought to
> ground by the control module, current can flow through a coil primary
> winding. The control module holds the ground for a ECC demanded dwell
> at which time the ground is raised, causing the coil to discharge.
>
> I want to monitor when each control wire is being held to ground.
>
> My monitoring device can take a 0-5v DC input.
> Do I need to be concerned with the current in the primary circuit that
> I will monitor voltage on?
> Is there a circuit design, or a discrete component that will scale the
> 12v on/off signal into a 0-5vDC output I can push into my DC input?
> This will need to operate fairly quickly.
>
> Other suggestions?
> Thanks
You have to deal with very high voltages(hundreds), when the ground
connection opens.
I would advice 100k to 1 megohm in series with two 4 volt zenerdiodes
anti parallel, to clamp voltage to 4 volts.
to make more of a divider, shunt 30k accross the diodes and a small
capacitor of 200 pf.(the last to stop capacitive coupling accross the
100k to your input).
Then maybe your electronics will stay alive :)
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