HappyTime 2 Cycle Ignition Circuit Explained with Diagram

[VTBikeman]

The timing is static. There is no time difference between the 0 crossing point and the firing point regardless of frequency (rpm). That could be "dwell time"- the time the coil takes to collapse its magnetic field. Anyone have an xray machine?
The firing on only the positive pulse is controlled by a diode.

 

[Scotchmo]

Different polarity on my motor

I found this post after doing some testing in order to design a charging system for my motorbike. I have a RAW 80 (66cc) motor but my polarity seems backwards from what was discussed. The CDI appears to be presenting its load during the negative half of the wave form. If I set my system up with a positive ground, any significant load kills the spark. By reversing the diode and making it a negative ground system, the lighting system can even tolerate a short without killing the spark.

I'm guessing that if there is an internal diode in the CDI/coil unit, the direction of the diode could be different than the one described here. I checked against a spare CDI/coil unit and it is the same as mine.

Has anyone else checked their proper ground polarity to avoid killing the spark?

 

[VTBikeman]

You seem to have hit on it. Mine is the Happy time motor and I think I got the polarity right when I tested it. If it works, go with it. I'd be careful about how much current you pull and you are restricted to a 1/2 wave rectifier. Use at least a 6A diode. A schottky diode will have less voltage drop so it will be more efficient.

I think it would work well to charge a battery when you don't need the lighting and use that. How much peak voltage do you get? You may need a small inverter circuit to kick the voltage up to the required value to charge the batteries. I use 10 NIMH AA cells in series for 12 volts at 2500 ma hours but I don't currently charge off the motor. I haven't had the time to fool around with it.

 

[Scotchmo]

The peak, unloaded voltage output from the half wave diode was about 9 volts. That was revving the engine while parked. It might produce a higher voltage at full throttle. I ran the output into a capacitor to "record" the peak voltage. At idle, I get 2 or 3 volts.

I'm using a 3 amp diode for testing. From my tests, it does not appear capable of putting out even that amount. I got about 500ma with a direct short.

The output voltage is correct for a 6v system, so that is what I'm going to use. 12v would be nice but I want to keep it simple. I plan on using a 6V 1.3ah SLA battery to run the lights. Maybe 4.5ah depending on the headlight that I choose. Charging will be done with the half wave rectifier. Across the battery poles, I will use a 5W 6.8v zener diode in series with a 5W 10 ohm resistor to prevent overcharging. The battery will handle the peak loads of the lights, horn, etc. when the lights are not used and I'm cruising at normal speeds, the diode will trickle charge the battery. If I rarely use the lights the zener will bleed off any excess current once the battery is full charged.

 

[570rm47]

umm well i was doing this just today, carefully chopping it apart a shave at a time then cracking it across the week points i made by shaveing it there is at least 1 more component i have a side of it exposed (do you love that cellotape insulated layering between the copper bet thats way better than epoxy)Will get my rotary tool back from loan tomorow and see if i can get a number off it. The capacitor appears to have "CBBB1" on the top line and "680nJ300AC" on the second line
Note the little board cant see evidence of anythinelse yet

 

[HeadSmess]

google "rohmell roll your own cdi" and read related threads...

already done, reinventing wheels...

 

[M_TRK]

I've recently rebuilt the ignition system on a B&S 130202-0598 (new points, condenser, magneto and flywheel), I failed to notice that there was a very thin transparent coating on the wire (the entire wire; under the black insulation and all) from the coil to the condenser itself. I had used the original wire going to the condenser and simply spliced it with the corresponding wire with the new magneto. It took me some diagnostics to ascertain the fact that the 2 wires that I twisted together to connect were in fact not electronically connected. Once I discovered this, I took a blade and a lighter to melt/scrape off the thin coating of both wires to expose the copper and then bam! I had a strong, blue/white spark. Hopefully this can be useful to anyone else that finds themselves running into snags when replacing parts on a points style ignition system.