New Type of Coil Driver? (Hall Effect Inside)
Posted: Tue Dec 02, 2014 7:56 am
So, this is just a little thing I thought up for driving an ignition coil efficiently and at "maximum power" (an optimum frequency).
Rather than doing the convoluted time constant calculations for your coil/capacitor and coming up with an optimum frequency for driving your ignition coil at, why not simply measure the magnetic field around the coil and switch current through the primary accordingly?
Here's the circuit I came up with. Basically, it uses the strength of the magnetic field around the coil to judge inductor "charge" and switch current accordingly. The two comparators and potentiometers are used to "trim" the sensor values.
Components (as far as the hall effect sensor is concerned) are tentative, as I don't really know any "recommended" linear hall-effect sensors (which I was looking to hopefully get some recommendations on). The opto-isolator (between the MOSFET and the output) would probably be homemade unless I can find a reasonable discrete one.
The pair of NAND gates forms a "combinational" logic block with the following truth table. The second gate is used to "latch" the first even after the second input goes low.
This circuit was initially going to use a pair of reed switches with a coil to "latch" the second one during magnetic field decay, but the fiddley-ness drove me to create the solid-state implementation.
It would require some measurement and adjustment, but nothing that can't be done quickly with an oscilloscope or even an Arduino.
Any comments/suggestions?
Rather than doing the convoluted time constant calculations for your coil/capacitor and coming up with an optimum frequency for driving your ignition coil at, why not simply measure the magnetic field around the coil and switch current through the primary accordingly?
Here's the circuit I came up with. Basically, it uses the strength of the magnetic field around the coil to judge inductor "charge" and switch current accordingly. The two comparators and potentiometers are used to "trim" the sensor values.
Components (as far as the hall effect sensor is concerned) are tentative, as I don't really know any "recommended" linear hall-effect sensors (which I was looking to hopefully get some recommendations on). The opto-isolator (between the MOSFET and the output) would probably be homemade unless I can find a reasonable discrete one.
The pair of NAND gates forms a "combinational" logic block with the following truth table. The second gate is used to "latch" the first even after the second input goes low.
This circuit was initially going to use a pair of reed switches with a coil to "latch" the second one during magnetic field decay, but the fiddley-ness drove me to create the solid-state implementation.
It would require some measurement and adjustment, but nothing that can't be done quickly with an oscilloscope or even an Arduino.
Any comments/suggestions?