the probes were reading DC only and 1:1

also, when I jumped out R1 & R2 (1.5K-ohm) and C2 (0.01uf) and nothing on output I measure VCC. My guess is that loading the output is sucking down my voltage.

is there a better combo to get 50KHz that the resistors and caps I currently use?

 

It occurs to me that it would be helpful to have a shut off safety mechanism in this circuit that is less destructive than the previous magneto-based version. The previous circuit got its power from the magneto, and through a series of diode‘s and capacitors created a pulse DC source that went into an SCR trigger very similar to the one I’ve got working now, but it had a small trace on it circuitboard that would blow out if the engine went around 500 RPM and of course that blown trace was about 2 inches inside of a cube of black epoxy. I would like to build something like that such that if the engine started to run away and got around 500 RPM that the electronic ignition would shut off and not come back on until you did something manually like reset a breaker or something.

I open the floor up for discussion.

 

I would like to build something like that such that if the engine started to run away and got around 500 RPM that the electronic ignition would shut off and not come back on until you did something manually like reset a breaker or something.

Please post a schematic of the exact circuit you are using at present, so that we can see what modifications would be possible to include that feature.

 

Please post a schematic of the exact circuit you are using at present, so that we can see what modifications would be possible to include that feature.

ok. I need to draft it - in between a real job… but I’m glad to.

 

Ok I’m almost done drafting it up. So many things happening at once that I have not given it much time.
On a side note: is there such a thing as a solid state toggle switch with memory? I’m thinking about the feedback coil of my mini transformer triggering this imagined toggle if the rpm gets too high. Then it would be locked in that state until a manual button press to toggle it back into action.

 

I’m thinking I make a 555 at say 7hz. Output to a comparator. Then I input my trigger pulses (max 7.5 hz) to the comparator. If not equal then nothing. If > or = then change the state of a flipflop. That flipflop controls the 12v in or the power to my main 555 power supply pin.
Result: you go to fast you shut off.

 

is there such a thing as a solid state toggle switch with memory?

Yes. It's called a 'latch'.

 

Hello all.
It's been a bit crazy - my wife's paternal grandmother passed.

The following is a copy of my working circuit. It is a theme and variation of another circuit posted by Ray Richter. I have updated the components and added some clarification notes and a proposed circuit board layout. I have not had the circuit board produced yet because I am working on a high rpm shut off addition to this circuit using an LM2907. That said, this circuit works and makes aggressive sparks that not only run my hit-n-miss engine (with the magnetic pickup coil for the trigger) quite well but also can put you on your butt if you are not careful.

 

Sorry to hear of your GMIL's passing. My condolences.

 

Sorry to hear of your GMIL's passing. My condolences.

Thanks Alec. It sucks but it was also a blessing. She was gone a long time ago via dementia / Altheimer's.

 

I've had another look at the circuit you attached in post #348 and don't see how the kill switch would work with diodes D1 and D2 present. If the kill terminal is grounded, the diodes would leave ~1.2V on the /SD pin of the IRS2104 but, if I'm reading the datasheet correctly, that pin needs to go below 0.8V to guarantee shut-down.

 

I've had another look at the circuit you attached in post #348 and don't see how the kill switch would work with diodes D1 and D2 present. If the kill terminal is grounded, the diodes would leave ~1.2V on the /SD pin of the IRS2104 but, if I'm reading the datasheet correctly, that pin needs to go below 0.8V to guarantee shut-down.

I can’t explain it fully but it works.
I want to explain it

 

Perhaps the 0.8V threshold only applies if the logic supply voltage is, say 5V (suitable for TTL logic). Since you're using a 12V logic supply the threshold could be ~6V (suitable for CMOS logic). Whatever, I don't see the need for those diodes. But hey, if it works then that's fine.