BT151s just showed up.

 

These parts are a few days off still

• NTC1
• TIP41C

 

A while back, someone here mentioned engine speed control.
In keeping with the hit-and-miss principal of this old engine, here's an add-on possibility which uses the Blanking signal from the above circuit to sense if the trigger pulse repetition period is shorter than a preset limit.

That would be me. But just "speed control" isn't what is needed. Speed control of a hit and miss is based on load not time. With out using the governor built into the original ignition I can think of no way this will happen.

Why use a "trigger coil"? Wouldn't a Hall type sensor work better? Like they use in a car engine, a crank position sensor.

This whole thing could have been up and running if it had been done with off the shelf automotive parts and there would be no troubleshooting and other BS involved. It's called the KISS principle.

 

That would be me. But just "speed control" isn't what is needed. Speed control of a hit and miss is based on load not time. With out using the governor built into the original ignition I can think of no way this will happen.

Why use a "trigger coil"? Wouldn't a Hall type sensor work better? Like they use in a car engine, a crank position sensor.

This whole thing could have been up and running if it had been done with off the shelf automotive parts and there would be no troubleshooting and other BS involved. It's called the KISS principle.

I agree. Right now the speed is controlled by how much gas is available at the carb. There is a regulator arm that moves a butterfly valve…

it’s maddening but there it is and I can’t change that at the moment.

it is currently running on the old ignition module but when that one goes I need to have this one ready.

there is a huge list of Kiss topics for sure. Trying to argue that with an anxious 80 yr old (my father) is the primary sticking point.

so now I Have the parts I think I need to make a homemade dc CDI and that’s were I’m going next.

I’m going to go back and review the proposed circuit and see if I can breadboard it

 

. @Irving thinks the timing cap is shorted to do this, but I'm not so sure. If I'm reading the UC3843 datasheet correctly I think shorting that cap would leave the MOSFET switched on

As per diagram in post #74 on page 4 it shorts the 'comp' input to ground which is the output of error comparator & input to PWM control. A low level here stops PWM generation and leaves MOSFET off.

 

As per diagram in post #74 on page 4 it shorts the 'comp' input to ground

Ah. That makes sense. Thanks for the link back. I think I missed that post previously.

 

What a crazy couple of days. Replacing the diodes restored the solar panel. Low back to making the ignition module.

 

I’m sorry, I left my notes at work… am I breadboarding the Jaycar circuit? I think that Jaycar circuit is a traditional AC CDI

 

I think I figured out the problem with my thinking… at least in one issue…

I can’t use the 12-350vdc circuit I have because I just need a transformer to make pulses - not a constant 350vdc.

so now I have all these bits and bobs but I don’t have the transformer (12-300 or close). I’m going to look to see if I can strip out and use the transformer on the HV circuit I have.

 

I think that Jaycar circuit is a traditional AC CDI

It's not AC as in 'powered off the AC mains', but (like most/all CDI) it has to create AC first by inverting DC, then raising the created AC voltage before rectifying it to HV DC.

 

Does anyone have the xfmr specs on this transformer? I cannot see any marking on it. I’m going to desolder it (this is from the one with the cracked PCB.

I guess I still have a lot to learn.

 

It's not AC as in 'powered off the AC mains', but (like most/all CDI) it has to create AC first by inverting DC, then raising the created AC voltage before rectifying it to HV DC.

so can I just substitute my power supply into the Jaycar schematic? Would inserting my HV generator work - would the SCR shut off?

 

Ok. Here is what I’m going to try and make using the HV power converter circuit I already have. What do you all think? It’s the Jaycar circuit with a little refinement.

 

A GM HEI ignition module is cheap proven and reliable.

Easy way to make a better and more reliable ignition than breaker points ( but you can use the points in place of a trigger coil too )

 

A GM HEI ignition module is cheap proven and reliable.

Easy way to make a better and more reliable ignition than breaker points ( but you can use the points in place of a trigger coil too )

I agree but it is all covered in Epoxy and you can’t see the parts, replace them or use it to teach. It’s a black box. It works but it’s darn frustrating.

 

Ok I have breadboarded most everything. I need some 0.1 and 0.01 uF caps and a 2M resistor. I need to get those parts and rig this up next to my spinning trigger magnet and hopefully see some sparks… so slow going.

 

If you use your existing 350V supply as is, that Jaycar circuit has no way of blanking it to prevent the SCR shorting it out. The big cap on the supply output might not like that. Any sparks you see might come from surprising places!

 

Ok. So I go and but a transformer and make Irving’s design…? What’s the name of that transformer brand again? Maybe I could use the transformer already on the HV board. I have no specs on it though.

 

You cant use that transformer in the Jaycar inverter.

 

Yes. I remember speaking about that. You recommended a different European brand that began with a W... Wyeth…? It’s in my notes at work. What is the name and part number again please? I’ll order one today.