I am currently working on a DIY quickshifter. This stops the spark for a very short time when changing up gears so that gears can be changed at full throttle.
I have a working circuit, but it currently has no protection from load dumps or transient voltages.
The quickshifter will be controlled by an Arduino microcontroller. When a gear change is detected the Arduino will stop the coils from sparking for a number of milliseconds.
Here is a basic circuit of how the coils are fired.
The red wire connected to the Pri pin on the ECU supplies a constant 12V to the primary coils. Once a signal is recieved by the relevant PNP transister the 12V feed is stopped momentarily and this causes a spark to fire.
I plan to cut the wire feeding the primary circuit of the coils between A and B and then connect these wires to my Arduino circuit. This circuit will be powered by another wire, labelled C above.
Here is the circuit I want to add to the motorcycle.
I need to add some protection to this circuit to protect the MOSFET and MOSFET driver. The datasheet of the MOSFET driver advises to use a bypass capacitor but doesn't mention the size I would need to use.
Please can someone recommend some improvements to this circuit in order for it to be protected when in use on a motorcycle.
Thanks,
David
Best Answer
Wondering if/how you solved this. I agree w/ mkeith above. You don't need to kill the 12V to the coils, you need to disallow it's interruption by bypassing the system transistors. You could do this by feeding 12V thru one large(er) MOSFET to all coil 12V inputs - thru diodes (so the coils don't crosstalk.) It would likely create a puff of black smoke and/or a tailpipe backfire. You're dumping raw fuel/air out into the exhaust and then firing fully (air/fuel)loaded cylinders after that. The flame will leak out of the exhaust valve and ignite what's' in the exhaust pipe. Sounds like noisy fun if you don't have mufflers to worry about. Backfires (exhaust explosions - not intake) will usually split the muffler depending on the construction. You may also want to blank out your injectors during this time. Injector blanking means lean cylinders but no spark to overheat... but power recovery might be a problem as the cylinders need to be reloaded with fuel once normal operation is restored (clutch released.) Your control switch could be a basic contact switch on the clutch. This could also be completely analog /w no micro(Arduino)...and thus no software...and thus faster. If you add the injector blanking function, you can always use it, or not. Injector blanking would involve denying drive signal to each injector. If they are individually fired you need a series switches(MOSFETs), one for each injector. If they all fire at once, then just interrupt power to all of 'em due to their only running on one channel, will suffice. If you're on carbs, your out of luck. ...Good luck.