I understand the circuit concept you are shooting at but I have no idea why you would have chosen those particular values of diodes etc…

that’s long game for me. For now I need it to work. That’s a cool idea of the second 555. Incidentally I only have LM555CN chips if that matters.

so if I get home and power up the clean new board and pull the jumper off what should I be measuring to see if the circuit “shuts off”? Do I need to bring home the oscilloscope from work?

 

ok you make me want to download that and start learning again. It sure has improved since I was using it with 5.25” disks on a 286 PC.

here is my progress.

It takes about 2.5min to simulate a 100mS runtime on an Intel i9-12900K running on 16 cores and 64Gb memory.. There are other simulators that will use the processors in my Quadro RTX A4000 GPU but they don't have the breadth of components etc that LTSpice has. It woud have taken about 15 - 20min on my previous i7-970 PC. I can't imagine running that on a 286, though I used to own one back in the day, about 1985-ish!

 

You have to take a look at this.
Some guy out of the blue sent me this.
He also sent a json file that I cant seem to post.

It is his take on a DC CDI module. I hope this doesn't turn into a rabbit hole (unless of course it works)

 

I understand the circuit concept you are shooting at but I have no idea why you would have chosen those particular values of diodes etc…

that’s long game for me. For now I need it to work. That’s a cool idea of the second 555. Incidentally I only have LM555CN chips if that matters.

so if I get home and power up the clean new board and pull the jumper off what should I be measuring to see if the circuit “shuts off”? Do I need to bring home the oscilloscope from work?

Mainly because it needs fast recovery diodes that can handle a few amps; IN4007 doesn't cut it here. I picked ones that were suitable in the LTSpice models, they wouldn't be what I'd spec for a build, I'd do a lot more research before laying out the PCB. There are some serious peak currents in this circuit, a breadboard isn't going to be representative. That Wurth transformer is around 15USD (13GBP). The Myrra one is only about 4USD. Again, its a case of finding one you can buy one off. Using a 12v 50Hz transformer backwards isn't going to work well as the inverter needs to run at 50-100kHz to recharge the capacitor at full engine speed. Here we have a max cycle time of around 10mS, or 12000rpm on a single pot 2-stroke.

 

Mainly because it needs fast recovery diodes that can handle a few amps; IN4007 doesn't cut it here. I picked ones that were suitable in the LTSpice models, they wouldn't be what I'd spec for a build, I'd do a lot more research before laying out the PCB. There are some serious peak currents in this circuit, a breadboard isn't going to be representative. That Wurth transformer is around 15USD (13GBP). The Myrra one is only about 4USD. Again, its a case of finding one you can buy one off. Using a 12v 50Hz transformer backwards isn't going to work well as the inverter needs to run at 50-100kHz to recharge the capacitor at full engine speed. Here we have a max cycle time of around 10mS, or 12000rpm on a single pot 2-stroke.

I'd go for the Wurth transformer - I think it would be well Wurth it (worth it)... ok sorry...

 

It uses a PIC uController - do you have the facility to program one? If not I wouldn't bother,. The inverter is just the classic inefficient TIP transistor oscillator.

Unfortunately the BOM is incomplete. The important stuff like transformer, power transistor, etc are not identified.

 

No I don't have access to the aforementioned programmer. So again - let's stick with the simple (2) 555 approach you are going with. Le me know if the LM555CN chips will do otherwise I'll start ordering parts from Amazon...

 

Hmmm it must go somewhere else.... otherwise its not doing anything...

 

Hmmm it must go somewhere else.... otherwise its not doing anything...

View attachment 275151

ok I backlit the board for this picture

 

ok I backlit the board for this picture

sorry I fell away for a little bit I had to go and pick up my daughter at school because she was fidgeting with a ring on her belt and got her finger jammed and everybody at the school went all freak out about it… She’s fine and if it was up to me I would’ve probably left it on there a little bit longer but she is fine and at home now and I have to go back to work and put in another hour.

 

@MarkySparky42 , is this a hit and miss engine?

 

@MarkySparky42 , is this a hit and miss engine?

Yes. Fairbanks-Morse 208, 12HP

yes it has a CDI ignition module because the internal magneto is broken.

 

yes it has a CDI ignition module because the internal magneto is broken.

They do repair them. Have you looked at the stuff on this site? https://www.old-engine.com/magign.htm
Another good one is Smokstak -https://www.smokstak.com/forum/

From working with them years ago hit and miss engines are different than a normal engine, ignition wise. The long dwell time kills most modules.

Where in Ohio are you?

 

ok I backlit the board for this picture

That makes more sense...



Removing that jumper and raising the input to 5v (or not grounding it) will disable the PWM to the MOSFET and turn the output off. The question is, how quickly does the output recover?

The way to do this is to set up a 555 timer like in my circuit above (the top one) connected to the trigger input and the output connected to the on/off pin (and ground to ground of course). A scope connected to the on/off input on one channel and to the gate of the MOSFET on the other should show the PWM stop and restart.

If you want to look at the 300v output make a simple HV probe as shown below, inside an insulated tube and use with x10 probe. DO NOT USE for mains voltages, only for this DC setup.

 

They do repair them. Have you looked at the stuff on this site? https://www.old-engine.com/magign.htm
Another good one is Smokstak -https://www.smokstak.com/forum/

From working with them years ago hit and miss engines are different than a normal engine, ignition wise. The long dwell time kills most modules.

Where in Ohio are you?

I’m sure I can do that but I really really want to do this as an ignition circuit. This is a wonderful learning experience for me and it is an act of service
I’m near Akron and Cuyahoga Falls

I’m relearning some long forgotten skills and learning new ones and my teacher has an English accent. It does not get any more awesome… except for when it works.

 

ok. I’m home. I was able to build the 555 circuit before I left from work. I didn’t get a chance to power it up or scope it but I’ll do that tomorrow.

the circuit you sketched above: is that the HV power supply just in a greatly simplified diagram?

 

That makes more sense...

View attachment 275173

Removing that jumper and raising the input to 5v (or not grounding it) will disable the PWM to the MOSFET and turn the output off. The question is, how quickly does the output recover?

The way to do this is to set up a 555 timer like in my circuit above (the top one) connected to the trigger input and the output connected to the on/off pin (and ground to ground of course). A scope connected to the on/off input on one channel and to the gate of the MOSFET on the other should show the PWM stop and restart.

If you want to look at the 300v output make a simple HV probe as shown below, inside an insulated tube and use with x10 probe. DO NOT USE for mains voltages, only for this DC setup.

View attachment 275175

Ok this is going to sound dumb but here goes.

can I hook up my voltmeter to the 300Vdc output and connect the jumper pins of the power board to a simple switch? Press and count… or is the drop off too fast? By recover you mean that when the power is restored how fast do we get 300Vdc again?
I think I answered my own question.
I’ll make the 555 circuit make square waves then I’ll post back.
I really should order you one of these marvels.

 

I got the two un-burnt power supplies in the post just now.

The left circuit has the output OUT V+ and GND

The right circuit has output of OUT V+ GND OUT V-

 

Please show me again what 555 circuit I need to build. I’ve checked in the lab and I don’t have any 2N7002, RFN10NS8D, BSB012N03LX3 or the transformer you reference. I wondering I can swipe these parts from a computer power supply or some other junk I have laying about….

 

You can simulate - download LTSpice free from Analog Devices - its got a bit of a learning curve but its worth it.

Incidentally, here's my version: I use a second 555 (or 1/2 a 556) to create a blanking pulse to turn the generator off when the trigger happens...
View attachment 275137

This generates about 400vDC with a proper transformer from Wurth, or about 300v with a cheaper one from Myrra

Can you suggest a part number for the super fast acting diodes that are not surface mount so that I can breadboard this together?

Can I use RFN10TB4SNZC9 diode?

I installed the spice software and it is updating a million things and I’m crashing. You’re probably long asleep.

I don’t know how to work with all these surface mounted pieces.

Please excuse all ramblings from this point on.