From: Harold Hallikainen <harold@mai.hallikainen.org>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Mon, 2 Aug 2021 09:58:21 -0700
Subject: Re: [EE] Honda M250 ignition waveforms
Thread-Topic: [EE] Honda M250 ignition waveforms
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> I think the voltages (when points connected) are way too small.  Is there
> a
> capacitor (condenser) across the points? it could be broken. Otherwise
> there may be another leakage path across the points.  (low oil shut off o=
r
> ignition key??)
> I was going to  suggest that the series resistance in the secondary side
> could be high, but the voltage with the points (and ?) disconnected look
> to
> be pretty much as I'd expect. I'd expect to see some ringing as well and
> maybe >150V peak if all was going well.
> Have you got something else you can compare it to? - even a motor mower
> might give you a clue as to what to expect.
> RP
>

Thanks! I think the voltage with the ignition coil is quite low. Note that
in this system everything is in parallel. The magneto coil, breaker
points, kill switch, capacitor, and the ignition coil primary are all in
parallel. Current builds up in the magneto coil with the points shorted as
the magnet passes by. Then the points open, and the current goes through
the ignition coil primary and the capacitor instead of through the breaker
points.

My brother had to replace the ignition coil, since it was falling apart.
It's possible that the replacement he got was not correct. He got it off a
recommendation on a web forum. It may have been incorrect. The service
manual on the motorcycle is very unhelpful. It just says to replace
everything. I think scope photos of what it should be doing would have
been helpful. Especially with the magneto and points driving a specified
resistive load.

Thanks for the comments thus far!

Harold



>
> On Mon, 2 Aug 2021 at 14:03, Harold Hallikainen
> <harold@mai.hallikainen.org>
> wrote:
>
>> Thanks for the comments thus far. I've attached some waveforms. I had to
>> break this into separate emails to stay under the 60 kB limit.
>>
>> TEK00002 - Edited.png - This is with the ignition coil primary
>> disconnected. It is the magneto output with breaker points operating.
>> Peak
>> voltage is about 40V.
>>
>>
>> Does anyone have any idea of expected waveforms?
>>
>> Thanks!
>>
>> Harold
>>
>>
>>
>>
>>
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