Hello all.
Im building an ignition component for a performance automotive application, and have struck a little brick wall. The actual ignition/coil firing side of things works perfectly, the problem is with a diagnostic funtion I need.
The igniter chip I'm using has a flag that gets set +5v when the current going to the coil reaches 4.5A. The IC itself will provide up to 8A of coil current, so the width of this flag pulse can vary depending on how much current is allowed to build up in the coil (which depends on the dwell time, the duty cycle of the ignition pulse).
I need this flag to turn on an LED as soon as it appears (when the current allowed to build in the coil reaches 4.5A). The LED needs to stay on after this point, aslong as the flag is regularly present... i.e the actual value of coil current isnt important, just that its being allowed to increase to more than 4.5A.
Ive tried a couple of things with an LM741, using it as a voltage buffer, with a diode to charge a capacitor quickly, which then discharges through the LED when the flag is no longer present... But am not having much luck,
Any help would be greatly appreciated.
Cheers all
Im building an ignition component for a performance automotive application, and have struck a little brick wall. The actual ignition/coil firing side of things works perfectly, the problem is with a diagnostic funtion I need.
The igniter chip I'm using has a flag that gets set +5v when the current going to the coil reaches 4.5A. The IC itself will provide up to 8A of coil current, so the width of this flag pulse can vary depending on how much current is allowed to build up in the coil (which depends on the dwell time, the duty cycle of the ignition pulse).
I need this flag to turn on an LED as soon as it appears (when the current allowed to build in the coil reaches 4.5A). The LED needs to stay on after this point, aslong as the flag is regularly present... i.e the actual value of coil current isnt important, just that its being allowed to increase to more than 4.5A.
Ive tried a couple of things with an LM741, using it as a voltage buffer, with a diode to charge a capacitor quickly, which then discharges through the LED when the flag is no longer present... But am not having much luck,
Any help would be greatly appreciated.
Cheers all