I need a circuit to make a magnetic trigger to replace the engines mechanical points

[circuitman1989]

I have a 1990's Briggs opposed twin engine with a "Magnitron" magnito but its been sitting for awhile and rat chewed through the spark plug wire. I have an old working opposed twin Onan 12v coil that want to use in it's place, but the briggs engine doesn't have mechanical points. Is there any way to make a circuit that is magneticly triggered (like a crankshaft position sensor on newer cars and trucks) to replace mechanical points?

Thanks in advance,
John

 

[cobra1]

Hi, are you in the UK?? I might be able to do better than give you a schematic, i actually built one of these a while back for an engine that was converted to run on Hydrogen. The device i built gave me complete control over spark timing by using a hall sensor on the Flywheel.

 

[circuitman1989]

Hi, are you in the UK?? I might be able to do better than give you a schematic, i actually built one of these a while back for an engine that was converted to run on Hydrogen. The device i built gave me complete control over spark timing by using a hall sensor on the Flywheel.

Thanks cobra1, I live on the east coast of the USA. But if you still have it, everything part is there, and it still works would you consider shipping it if I paid for the shipping or would you consider building me a new one?

 

[cobra1]

building another wouldnt be a problem, it would just be the unit itself though. you would need to find an induction coil, (sounds like you already have one) it would have the hall sensor on it already so all you have to do is fit it to the flywheel and your pretty much set.

 

[circuitman1989]

cobra1, I'm just wondering if the circuit you built has a "tachometer singal output" like the one in the picture I've attached. Also can you make a "pulse multiplyer" to take one pulse per rotation and turn it into four pulses per rotation so I can use a 4 cylinder tachometer (BTW, I watched the mechanical points in my 8hp briggs while turning the engine over by hand, the points are normally open until the points plunger hits the flat spot on the crankshaft... So it is one pulse per one full rotation, Not one pulse per every two full rotations.)

 

[cobra1]

Is this a single cylinder engine??

 

[cobra1]

I just saw your other post, as you have a single cylinder engine, you only require a single spark every other revolution, the other spark is called a waste spark. It is a problem mechanically to stop this waste spark as it requires gearing to stop it, so manufacturers just let the waste spark occour as in a petrol engine it doesnt cause a problem.

In my hydrogen engine i had to remove this wast spark and had to build a gearbox to deal with this.

Since the ignition module works using a hall sensor it lends itself quite readily to being used as a tacho, if you would like i could look into making an ignition unit with a built in tacho that has an LCD display with the RPM displayed.

 

[circuitman1989]

Well, when I found this engine and tractor for 25 dollars US about three days ago, I kinda decided to to use this 18hp briggs instead of my 8hp briggs for my rear engine vertical shaft engine go-kart project. I figure that with the proper modifaction to my 1973 peerless 600 trans axle (Ex. I'm upgrading it from 3/4inch axle shafts with a diffrentchal to a 1inch go-kart 'live' axle, but with minimal modifaction to the housing and inside gear set that the axle shaft slides through) and the proper pulley size ratio, I should be able to use the the 18hp in mostly stock form. But since I will sit infront of the engine I wanted to use the tacho I already, because I wanted the Hall Effect Trigger circuit mounted as close to the engine as possible and I wanted the tacho mounted up in the front of the go-kart near the steering wheel. here is a link to the tacho I have but I bought it from an Advance Auto store instead of from jegs.com Sunpro CP7911 Sunpro Super Tach II & Mini Super Tach II If you could make the circuit from my other thread and intergrade it into the Hall Effect Trigger circuit cause all I really want is to have the Hall Effect Trigger circuit and be able to use the tacho I already have but to do that I'd need the other circuit as well.