This is what i made up as a replacement CDI system for an engine.View attachment 275575View attachment 275576

I could potentially use my 12vDC to 300Vdc circuit to make the upper circuit… then I just need to construct the lower portion…

 

Confirmed. Coil (-) terminal has a jumper to casing.

That looks like the ignition coil? I was asking about the trigger coil.

I've been musing over making a more sensitive trigger circuit and offer the following one. It uses one comparator of an LM339 quad comparator chip for sensing the initial negative-going half cycle of the trigger coil (so coil polarity matters). With the components shown a ~20mV signal can be enough to trigger things, but adding series resistance to the trigger coil can reduce sensitivity if required. High sensitivity requires shielded cable from the coil to the electronics.
I can't bear to see things going to waste , so pressed the other 3 comparators into use for the timing functions. No 555s !
Q1 drives the SCR gate.
The R4C2 time constant sets the width of the enable/disable window.
The R6C3 time constant sets the delay before the SCRgate pulse starts.
Total current draw for the circuit shown averages less than 2mA, so that shouldn't flatten your battery too quickly!

 

That looks like the ignition coil? I was asking about the trigger coil.

I've been musing over making a more sensitive trigger circuit and offer the following one. It uses one comparator of an LM339 quad comparator chip for sensing the initial negative-going half cycle of the trigger coil (so coil polarity matters). With the components shown a ~20mV signal can be enough to trigger things, but adding series resistance to the trigger coil can reduce sensitivity if required. High sensitivity requires shielded cable from the coil to the electronics.
I can't bear to see things going to waste , so pressed the other 3 comparators into use for the timing functions. No 555s !
Q1 drives the SCR gate.
The R4C2 time constant sets the width of the enable/disable window.
The R6C3 time constant sets the delay before the SCRgate pulse starts.
Total current draw for the circuit shown averages less than 2mA, so that shouldn't flatten your battery too quickly!
View attachment 275623

My apologies.
The trigger coil is just a two wire “electromagnet”.


that coil of wire used to plug into the black box… two wires from the coil and two wires going out to the ignition coil.

it’s about 1” long And it has a 3/8” bolt going through it. It is mounted in a slotted L shaped bracket that can adjust pitch up and down as well as allow the device to slide forward and back.

looking at the old circuit board - one wire was connected to ground and the other to the trigger input.

I wish I had access to something that could easily dissolve rock hard epoxy potting compound. I’ve tried boiling and picking and I’ve tried soldering iron and picking but nothing with solvents. I wonder if a high pressure steam source would work…

 

That looks like the ignition coil? I was asking about the trigger coil.

I've been musing over making a more sensitive trigger circuit and offer the following one. It uses one comparator of an LM339 quad comparator chip for sensing the initial negative-going half cycle of the trigger coil (so coil polarity matters). With the components shown a ~20mV signal can be enough to trigger things, but adding series resistance to the trigger coil can reduce sensitivity if required. High sensitivity requires shielded cable from the coil to the electronics.
I can't bear to see things going to waste , so pressed the other 3 comparators into use for the timing functions. No 555s !
Q1 drives the SCR gate.
The R4C2 time constant sets the width of the enable/disable window.
The R6C3 time constant sets the delay before the SCRgate pulse starts.
Total current draw for the circuit shown averages less than 2mA, so that shouldn't flatten your battery too quickly!
View attachment 275623

Uh wow!
This smokes anything I thought of…
What is that file attached?

shielded cable is not an issue - we have aluminum foil!!!…. Kidding.
I want to take a trigger coil apart and found the windings and wire gauge at some point.
Ok so I have to add a few more parts to the list. Including that thermistor from the Jaycar circuit listed above.

 

That looks like the ignition coil? I was asking about the trigger coil.

I've been musing over making a more sensitive trigger circuit and offer the following one. It uses one comparator of an LM339 quad comparator chip for sensing the initial negative-going half cycle of the trigger coil (so coil polarity matters). With the components shown a ~20mV signal can be enough to trigger things, but adding series resistance to the trigger coil can reduce sensitivity if required. High sensitivity requires shielded cable from the coil to the electronics.
I can't bear to see things going to waste , so pressed the other 3 comparators into use for the timing functions. No 555s !
Q1 drives the SCR gate.
The R4C2 time constant sets the width of the enable/disable window.
The R6C3 time constant sets the delay before the SCRgate pulse starts.
Total current draw for the circuit shown averages less than 2mA, so that shouldn't flatten your battery too quickly!
View attachment 275623

here is a scope picture of the Trigger coil at start speed… the at 500 rpm

 

This is all thats needed to trigger the SCR in the circuit i posted. Its salvaged from a scraped inverter generator engine. It is magnetic so only needs a screw similar in the picture, screwed into a flywheel.

 

What is that file attached?

It's the LTspice simulation file, for anyone that wants to play with the circuit.
If the trigger coil can generate ~1V peaks at the engine start speed then the extra sensitivity my posted circuit offers is probably not needed.

 

This is all thats needed to trigger the SCR in the circuit i posted.

An inverter-generator runs at 3000 rpm or 3600rpm. The output of the sensor shown in post #166 would, of course, be much lower at the OP's 425rpm, so might not be enough to trigger the average SCR.

 

An inverter-generator runs at 3000 rpm or 3600rpm. The output of the sensor shown in post #166 would, of course, be much lower at the OP's 425rpm, so might not be enough to trigger the average SCR.

thencrappy little circuit I started with was able to be triggered by the coil. However it was powered by the wall wart and had internal characteristics that allowed the scr to shut off and fire again.

I just ordered the components in all of your circuits and and hopefully within a week I’ll be able to put something together. It’s a fun process except for all this waiting.
I wish we were all in a little lab together - we would get this done in two hours I’m sure. Between the simulation software and past experience we could make some thing that would make Tesla blush.

 

I'm intrigued. If I'm reading your second scope shot (post #165) correctly those pulses occur at 20Hz. Yet your max engine rpm has a spark pulse rate of 7Hz. ??

 

Yeah. I need to clarify… I put the trigger magnet on a motor. That was at a really fast rate. It was not in the engine. Sorry. That’s misleading.

 

The parts I ordered won’t be here till the 19th.

 

Pulling a few strings I was able to get some parts here sooner.

• BT151
• 1N5408 - Got them
• 1N4004 - Got them
• NTC1
• TIP41C
• TIP122
• LM339 - Got them

 

Quick side question:

I have a diode on my solar panel that I suspect is faulty and that is why my panel is not charging. I need help translating the part number.

20SQ045 M0A 14. Could be MOA


I need a number Amazon recognizes.

 

It's one of these.

 

The TIP122 (10 pack) was just delivered.

 

Those TIP122 will probably need a heatsink in that circuit... anything above 2W dissipation and they'll burn out without. What transformer have you sourced?

 

Hey Irving,

I didn’t source the transformer yet. I thought we were going to use the HV power supply I have already.

 

Here's another option for the trigger circuit :-

This should work with a trigger coil voltage down to 0.3V.
Nand gates U1a/b form a monostable, with a blanking pulse duration ~3mS set by R7C3.
U1c/R5/C2 make a ~1.5mS pulse for firing the SCR via Q1. I've added a Kill-switch.

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.
If the engine goes above a set speed a Disable signal output goes high amd can be combined with the Blanking signal to turn off the HV supply until the revs drop below the limit.

The blanking pulse turns on Q1 to discharge C1. The c1 voltage then ramps down at a rate set by the pot and R6. If it goes below the switching threshold of U1a (i.e the blanking pulse repetition period is long enough) then the latch formed by U1a/U1b is set. Just before the next expected blanking pulse occurs the latch is reset via U1c. The brief interval between this reset and the next set is bridged by R5C3, so that the Disable signal output from U1d remains low.
The exact way in which the HV supply is turned off depends on the way in which the jumper is presently wired, which is a bit of a mystery to me. @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: something to be avoided. From the pics of the circuit board it looks to me as though the ground pin of the IC is being switched?

 

I love the idea of a speed governor.
Amazon just delivered more toys. I’m headed home to see what they are. I think they are the BT151s and I have some heat sinks now too.

what do I start building? What’s the simplest… beside that 555 square wave generator?…