small engine electronic ignition

Ron Thompson wrote in article ...

When I managed a NAPA store, we sold an inexpensive (under $20) electronic ignition conversion for B&S among others.

Bob Paulin - R.A.C.E. Race Car Chassis Analysis & Setup Services

David

Thanks, that's the idea. But I was looking for the home built circuit.

Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA

The ultimate result of shielding men from the effects of folly is to fill the world with fools.

--Herbert Spencer, English Philosopher (1820-1903)

Try

All I did was google for "electronic ignition circuit" This one is battery operated. All the home made ones I seen use a battery. ERS

Yeah, me too. Not much good on a lawnmower. I thought I had the other one saved on my computer, but I can't find it.

Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA

The ultimate result of shielding men from the effects of folly is to fill the world with fools.

--Herbert Spencer, English Philosopher (1820-1903)

I don't think that those "electronic ignitions" for lawnmower engines are anything more than a hefty zener diode. I'm sure that there must be a small-engine group (or 10) somewhere on the Internet where you could get a more definitive answer. In my fuzzy experience, you just bolt "the part" to a grounded part of the engine and hook it's one wire to the points connection. It works fine, and resultantly I doubt if they have been putting mechanical points in lawnmowers for the last 15 or 20 years.

I run a communications shop and we have drawers full of parts, some of which would likely do the job just fine. That said; if I needed that part, I would go to somewhere where they sell lawnmower parts and buy one. My time has a certain small amount of value to me.

Vaughn

Ron- I have used the ones you can buy for about 10 bucks. Some in plastic cases and others in metal cases. They all worked perfectly. Interestingly, B&S used some kind of coil in their electronic ignition to sense the magnet on the flywheel. And these ignitions were not that reliable. The ones you buy must sense the voltage build up and fire then. In a magneto ignition system the magnet needs to be passing the coil when the points open to get a good spark. I don't know how the retrofit systems know exactly when to fire. Different magnetos will have different voltages. The first ones I saw had to be bought for the right engine but the last one I bought said it would work on any engine. And it worked on a B&S, Tecumseh, and a japanese made weedwhacker motor. ERS

That said; if I needed that part, I

That's it. When you need a part that's un-obtainable, make one. On a part that takes 3 or 4 hours to make, and you can buy the thing for 10 or 20 dollars... forget it.

Jim Kovar Vulcan, Mi

so, Japanese weeds are different from American weeds?

How about this one:

Robert

On Wed, 09 Jun 2004 01:40:14 GMT, "Jon Grimm" wrote: No, well, maybe, but that's not the point. The japanese ignitions were different from the american ones. In fact, the american ones were actually made in the USA. ERS

Thanks, but it requires a battery. To the "just buy it" crowd, I haven't found one locally and I haven't worked for over two years. Money is scarce.

Ron Thompson On the Beautiful Florida Space Coast, right beside the Kennedy Space Center, USA

The ultimate result of shielding men from the effects of folly is to fill the world with fools.

--Herbert Spencer, English Philosopher (1820-1903)

Now, why would a Zenner diode create the KV necessary for a spark?

Do you use Zenner diodes for RF generation too?

Ted

It can act just like a set of points. It allows the voltage to rise to a certain point, where it suddenly conducts, which collapses the magnetic field. The collapsing field cuts the turns in the coil creating a spark. (I think)

Used mostly in DC power supply circuits and in circuit protection, come in many voltages and physical sizes depending on power.

Vaughn

Sorry to hear about that...

I understand. Then watch your local trash piles and scrounge (recycle) what you need. Get someone who really knows to confirm, but I think most of the lawnmowers that you find in the trash these days will have electronic ignition. Electronic ignition *must* be cheaper than mechanical points.

Early in the summer is probably the best time of the year to find junked-out lawnmowers as people are facing new heavy growth and junky lawnmowers that barely made it through last year's season.

Vaughn

Vaughn

I seem to remember something else for that purpose. Like a zener, it does not turn on until it reaches a threshold voltage, but unlike a zener, it does not remain at that voltage drop -- instead it switches to an extremely low voltage drop. (Consider it to be like a Zener diode connected between the gate an anode of an SCR, so when things reach the right voltage, the SCR is turned on, and all the current is dumped into the coil.

Enjoy, DoN.

Ron, Is this some kind of a special project you are working on, or do you just want to get your lawnmower running? If it's a case of just getting a mower running - provide some specifics like engine name, numbers, etc., and either I or someone else can probably help you out. Ken.

Got it backwards, kinda. The votage increases, but there is no current until the zener fires. The zener firing would BUILD the magnetic field, not collapse it. Might still work if the field could build as fast as opening points allows it to collapse. But some how you need to collapse that feild too - which MAY happen effectively when the zener stops conducting. Only problem is, the coil "rings" and the zener would likely false trigger, killing the spark prematurely.

I suspect there is something a bit fancier than a Zener in the little box.

Last one I bought a couple of years ago cost me $9.95 at Princess Auto. For that price I can't source the parts, pick them up, and plug in the soldering iron, much less fiddle around trying to make it work, and I'm a cheap beggar.