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Hi Lucky,
Ive been thinking about your diode pack tester for a while now. I have
had motorbikes myself, and i know many people who have motorbikes.
Problems with the charging system can be a headache for many people.
Ive read through 'Dave's Yamaha Vision Page' which i think is excellent
very informative and very well written, and touches on many problems i
have had to deal with. It also mentions 'Lighting Coils' which i haven't
met before. I get the impression that they are a bit of a off-roader
item, intended to lighten the overall weight. I would like to find out
more about these 'Lighting Coils'.
Back to the diode pack tester, i think this is a fairly basic request,
and i think that a fairly basic circuit could be made to do this job.
I assume you would be making this unit yourself, and presumably you
have done this job of testing the diodes in the manner described in the
handbook, that is by checking each one individually in both directions
in order to see by means of a small electric lamp, that each one will
conduct one way, and will not conduct the other way.
I presume you have done this job and therefore realise it is really
simple, and you rightly assume that some sort of circuitry could be put
together to do this for you.
I have looked at your circuit, and yes the concept is ok. It is clear
that you have replaced the manual actions of touching wires on the
diodes each way round, with two switches which when operated alter the
connections to try the supply each way round, and again on the other
bank of three diodes.
This shows that you have a clear understanding of what you want the
circuit to do.
I prefer to use filament lamps to do these sort of tests because LEDs
will often light up quite adequately on fairly small currents, a
filament lamp of about 21 watts will require just under 2 amperes to
flow through the diode under test and i feel that is a better test.
I know headlamps can be much more than that, but the load would be
spread over them all normally. So i wouldn't use a headlamp on them
individually.
The LEDs would be more suited to checking for leakages, that is the
current that gets through 'the wrong way round', since these diodes
are connected to windings that can give much more than 12 volts out,
Dave's site puts some at around 50 volts no load, then maybe two or
even three 12 volt batteries would be a fairer test. This could test
the reverse current leakage at 24 or 36 volts.
You may ask: "Why check them at more than 12 volts when its a 12 volt
system?"
Well the reason is that the drive to the diodes is AC, which goes just
as far negative as it goes positive. When it goes positive and holds
the battery at 12 volts thats fine, but then it goes negative to minus
12 volts ... so the diode has twenty four volts across it, and its not
supposed to let any current leak back out of the battery.
If the engine were started with no battery connected, or a dry battery
the diode would have the un-loaded output voltage to contend with.
Which can be quite high, Dave's site puts it at about 50 volts on each
winding. I would expect those diodes to withstand about 100 volts in
the reverse direction to be safe.
Without making too much of it, i would guess that two or three 12 volt
batteries in series would show up any likely failures.
Making test equipment using chips and logic circuits can be difficult
and very frustrating for someone who is unfamiliar with such work.
I would suggest using a rotary switch instead.
When wiring up to a rotary switch, one can follow the wire with your
eyes, you can see which lug or connector on the rotary switch is
touching on each bit. You can compare it with your diagram, and see
that current should flow with each switch position to each lug or
connector.
Using a rotary switch one could follow each setting in turn by looking
at them and following where they go.
I don't know if you are still considering suggestions for this tester,
if you are you may like to look at this.
Regards, John