• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Pointless magneto internal schematic ?

Jeff Nading

Member
Hello all, new here, just thought I would see if anyone might have a schematic on the internal workings of a pointless magneto, or could help me design one, as I would like to build my own to eliminate the points on a 12 HP B & S engine for my riding lawn mower. Also very much interested in building a small Tesla coil, if anyone might have a schematic on that, thank you, Jeff.
 

KeepItSimpleStupid

Well-Known Member
Most Helpful Member
They are cheap. http://www.jackssmallengines.com/Products/Universal/Ignition-Part/MEGA-FIRE-IGNITION You can sometimes get it for half that. SomewhereI foun a page with slightly different modules. If you search ETO, one of our members reversed engineered one and built it.

I installed one on a small lawn mower. I don;t know what I will do with a Vintage Tecumseh engine. I believe I have the part to put a stock electronic ignition on it. With the stock version, you have to change the timing which is a flywheel insert. There is a few other parts that also need to be changed as well.
 

tcmtech

Banned
Most Helpful Member
You could just stop by your local scrap yard or dump ground and take the ignition system off a junk engine. There are only about 3 main B & S flywheel sizes used on the vast majority of lawn and garden engines so if you find one that looks like its about the same engine size as yours the odds are the ignition magnetos are interchangeable.
 

Jeff Nading

Member
Thanks guy's for your input, but I would really like to build the circuit. Thought about using a Hall effect to create an on off pulse as the magnet on the fly wheel comes around, thus making and breaking the primary circuit of the magneto, causing an induction into the secondary coil, thus causing the spark plug to fire.
Yes it would be easy enough to buy one, EBay sells them for under $20, but I just like knowing what makes things tick and building things myself. To show you what I mean please view some my videos on YouTube @ my channel "Jeff Nading" , thanks Jeff.
 

gary350

Well-Known Member
The old antique Hit & Miss and Throttle Governer engines used pointless mags. Some of the old farm tractors used them too. You can probably buy one on Ebay. They are built like the EI laminations of a transformer but a magnet makes up part of the EI constructions. I have never taken one apart to see if it has 1 magnet in the center of the E or 2 magnets at the outer edges of the E. When the I is placed on the E the magnet holds it in place and the magnet field is completed. If you pull hard until the I comes off the magnet field colapses and the coil sparks. You will need about 20,000. turns of #30 enamel coated copper wire. The old magnets of 100 years ago were not very power compaired to todays magnets so you can probably build one with a lot less turns of wire.
 

debe

Active Member
This circuit can be constructed to replace the ign points in a magneto ignition system. Ive fitted it to my Victa 2stroke mower. You just remove the points & condencer, & fit this circuit in its place on the ign coil. Depending on the polarity of the pulse from the coil, the unit may have to be connected the opposite polarity. The circuit is actualy a copy on an Atom Ign module that's no longer produced.ATOM MOD red circ.jpg ATOM MOD.10.JPG ATOM copy on VICTA.JPG
 

Jeff Nading

Member
The old antique Hit & Miss and Throttle Governer engines used pointless mags. Some of the old farm tractors used them too. You can probably buy one on Ebay. They are built like the EI laminations of a transformer but a magnet makes up part of the EI constructions. I have never taken one apart to see if it has 1 magnet in the center of the E or 2 magnets at the outer edges of the E. When the I is placed on the E the magnet holds it in place and the magnet field is completed. If you pull hard until the I comes off the magnet field colapses and the coil sparks. You will need about 20,000. turns of #30 enamel coated copper wire. The old magnets of 100 years ago were not very power compaired to todays magnets so you can probably build one with a lot less turns of wire.
Thanks Gary, I don't know why I did not know that, my wife works for a tractor company, I will check into this, Thanks again, Jeff.
 

Jeff Nading

Member
This circuit can be constructed to replace the ign points in a magneto ignition system. Ive fitted it to my Victa 2stroke mower. You just remove the points & condencer, & fit this circuit in its place on the ign coil. Depending on the polarity of the pulse from the coil, the unit may have to be connected the opposite polarity. The circuit is actualy a copy on an Atom Ign module that's no longer produced.View attachment 91856 View attachment 91857 View attachment 91858
Awesome, thanks Debe, I more than likely have most of these parts here at the homestead, I'll definitely build this circuit and let you know how it goes, Jeff. https://www.youtube.com/user/nadingjeff
 

debe

Active Member
Yes the orange wire is supposed to be red. But the polarity realy depends on the polarity of the pulse from the coil, not necessarily fly wheel rotation. Its a case of try one way, if no spark try other way round. On the Victa lawn mower in the picture, the red wire goes to frame of engine. On one of my outboards its the other way round. In the circuit diagram the Red wire is to the Collector of Q1 & the Black wire is to the Emitter of Q1.
 

dr pepper

Well-Known Member
Most Helpful Member
Your engine will run better with a little timing advance, you might be able to get a timing curve from B&S.
 

Jeff Nading

Member
Yes the orange wire is supposed to be red. But the polarity realy depends on the polarity of the pulse from the coil, not necessarily fly wheel rotation. Its a case of try one way, if no spark try other way round. On the Victa lawn mower in the picture, the red wire goes to frame of engine. On one of my outboards its the other way round. In the circuit diagram the Red wire is to the Collector of Q1 & the Black wire is to the Emitter of Q1.
Ok, thanks debe, got it, Jeff.
 

debe

Active Member
As far as I can see these are modules I pulled a part if any one wants to experiment. The resistors are deposited & trimmed on a Ceramic substrate, & the capacitor is a Chip capacitor. The circuits are allthe same but the values changed. The best success ive had is with the Red module circuit in post 7. These pictures are of the Red module dismantled.ATOM IGN mod.1.jpg ATOM IGN mod.2.JPG ATOM IGN mod.3.jpg
 

Latest threads

EE World Online Articles

Loading

 
Top