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I am in the automotive industry. I am working on a little project, where the engine computer originally uses MOSFET to drive an earth to charge up an ignition coil, and by cutting the earth, it fires the spark into the cylinder.

I would like to turn this earth back into a 5 V square wave, so I can use different type of ignition coil, where the MOSFET is built into the ignition coil.

So basically, on the original connector, I have a power supply which can range between 12 V to 15 V generated by the car's alternator. I have a constant earth, and the 3rd pin is the earth signal to charge up the primary coil in the ignition coil.

All I need is a 5 V square wave reacting as fast as possible to the to the earth signal, and will tolerate the hovering voltage of the car's alternator. And the charge time for the ignition coil is generally between 2-5 ms.

I have the basic idea of using a voltage regulator and a PNP transistor to create the signal, I am just not sure of how to build the circuit safely for my application with resistors and capacitors.

Any help would be appreciated.

Greenonline
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Jin Zhou
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    Use the gate signal to the MOSFET as your starting point. – Andy aka May 08 '19 at 14:57
  • If you are "in the automotive industry" you should probably be talking to whoever at your employer designs these things professionally. If you are just a hobbyist experimenting around with a small non-automotive engine you might go after either the MOSFET gate drive circuit, or substitute a resistor for the coil and measure that. But this is probably not viable for an actual "automotive" application, as these systems long ago became far more complex and dynamically self tuning, in a way likely to interact poorly with your experimental replacement. – Chris Stratton May 08 '19 at 14:57
  • It is not typical for mobile vehicles to have a connection to "earth". Please consider using "ground" instead. – Bort May 08 '19 at 14:57

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schematic

simulate this circuit – Schematic created using CircuitLab

Marko Buršič
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