Designing CDI for old russian Kovrovec Vozhod 175cc

[Eviltech]

Hi Giys!
For 3 weeks now i am designing a CDI circuit to replace the original switch and cam shaft operated ignition. If the bike had a DC and battery instalation it would'nt be a problem, however the bike is all AC. AC is operating the ignition, headlight and rear signal light and brake light. So i have no DC on the bike and the worst is there is no regulation of any of the generator's outputs. What happends when i put a rectifier circuit on the 6V AC output? I get anywhere from 5V to 55V DC on the output, depending on the engine RPM. That makes using a normal voltage regulator impossible. Anyhow, i also need a way to get the voltage up to at least 100V from kickstarting to be able to charge the capacitor for the coil to actually be able to fire a spark. Advance is another issue. I have seen old electronic ignitions which uses a voltage triggering circuit which gets the signal from the sensor coil. The bike has no such coil. I believe i can use a combo between the original swich and the generator's coils. Also the ones i have seen were 4, 6 ot 9 poles magnets and this one uses an 8 pole rotor.
Any sudgestions are welcome!

[Eviltech]

Ok, update:
I am using the 6V ouput on the generator and a 9V transformer to step them up to >100. I'm using high speed diodes rated at 1A 200V (2 in series for the high voltage part). Parralel to the main capacitor i have connected a 300V zenner diode so i don't blow it up. Low voltage side - same diodes in full wave rectifier circuit. 4X470ohm resistors in parralel conected to a transistor backed zenner at 12V. Problem is the voltage generated  with kicking the kickstarter is not enough to turn on the thyristor so it can discharge the stored power in the high voltage cap. Using 2 LiIon batteries in series however is enough and the engine starts without any effort. I still don't have advance circuitry. I do not want to use digital circuits/microcontrollers for it. Only analog stuff!

[Strada916]

http://www.jaycar.com.au/productView.asp?ID=KC5466

This may help you a little.


What about retro fitting the electrics with modern battery system? You could use a small battery as you have no electric start. The alternator can have its insides retro fitted. provided its not internal to the motor.  That way you'll have nice constant head light brightness etc.

just some ideas

[Eviltech]

http://www.jaycar.com.au/productView.asp?ID=KC5466

This may help you a little.


What about retro fitting the electrics with modern battery system? You could use a small battery as you have no electric start. The alternator can have its insides retro fitted. provided its not internal to the motor.  That way you'll have nice constant head light brightness etc.

just some ideas

It is internal to the motor as in all the new bikes. And it's not an alternator it's a constant magnet generator. The problem i have with it is that i can't think of a circuit that can handle such high tolerances of the input voltage so i can use it to charge the battery and run the rest of the components of it... It needs to disapate about 55W when the headlight and brakelights are off so i dont blow up the battery, but i don't want to change the outside apearence of the bike. It's retro and i want it to remain that way. BTW i want to be able to start it even without a battery because the vibrations on it will probably just kill it anyway.

[Eviltech]

Ok, update:
  I am using the 6V output on the bike to generate a small signal to trigger the thyristor. Using a 33ohm resistor and a 13007 transistor with a 12V zenner i am limiting the output voltage to 12V. That's after the full wave rectifier. Using the original crank swich and the positive wave from the generator i am generating a trigger pulse for the thyristor.
  High voltage side:
Using the 6V AC and a small 9V tranformer conected as step-up transformer i am getting the higher than 100V needed for the capacitor. In parralel with the capacitor tere is another 13007 and zener diode combo, but this time to limit the output to 300V so the capacitor doesn't fail. Today i tested it for 50 km and it worked flawlessly! Tonight it's getting an epoxy resin bath

[Strada916]

Nice work good effort. Some pictures schematic of your circuit??

[Eviltech]

Soon, i'm not in town right now, maybe friday night