Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Nick Hull
 
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Default $400 question; Igniter for ATV

Between the flywheel pickup coil (magneto) and the high voltage coil for
the spark plug there is a black box that controls the spark and its
advance. This box on My Kawasaki 3-wheeler is called the Igniter and
this simple tiny circuit board costs $400! It was designed before 1982
and contains one IC and a bunch of discrete components. There has got
to be a better (cheaper) way to do this.

The spark starts at 10 deg before Top Dead Center and advances to 40 deg
before TDC by 2000 rpm. Since electronics cannot advance time
apparently the pickup is at 40 deg BTDC and the pulse is delayed to 10
deg BTDC at low speeds. If the timing delay fails the spark reverts to
40 deg BTDC for all speeds, meaning the engine cannot run at low speeds
therefore cannot be started. Bad idea.

How could this black box be designed using components availiable today
to control the spark advance, preferably adjustable or programable so it
would work in a wide variety of ATVs etc? If possible It would be
preferable to have the failure mode at low speed advance. Certainly I
would hope for a price below $400. All suggestions welcome

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/
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Default $400 question; Igniter for ATV

Nick Hull:
Year and model number of ATV ? .... and how many cc engine?
electricitym

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G
 
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Default $400 question; Igniter for ATV

There was a simpler (for us to see) way in the past....a mechanically
advanced "breaker plate" which originally mounted the points and later
perhaps just a pickup. For the manufacturer, what you have is likely
simpler. As it sounds like you got your igniter apart, is it repairable
(or was it a destructive process.....potted etc)? Most likely what you
have is a pretty simple circuit - why not reverse engineer it and either
repair what you have or build your own with similar but perhaps more
readily available components. Your cost to buy that unit has little to
do with the cost of its component parts and more to do with supply and
demand and typical lack of standardization.

You mentioned a failsafe mode but then answered your own question by
noting that it might take extra circuitry to insert the delay (just one
possibility for failure). One such system used in the past was to
trigger the ignition coil (i.e. to be an igniter) via a capacitor
discharged using an SCR (CD ignition) - Timing voltage was picked up via
a coil being swept by a magnet on the flywheel (small engines). Advance
and retard were effected by nothing more than a simple RC circuit (fixed
time constant) which was overun as the engine sped up (capacitor didn't
have time to charge or delay the build up of the trigger for the SCR).
These types of modules often had nothing more than a few diodes, couple
of resistors and caps and of course the SCR. They MAY have used a
seperate supply coil (Dirt bike with no battery) which built system
voltage just before the ignition was required......this could have been
supplied by a battery as well though (as supplied by for cars and trucks).

With older mechanical technology you faced similar problems to what
you've experienced. The breaker plate (or perhaps just a moveable
breaker cam) could be "stuck" at some advance anywhere between low and
high speed (not to mention the points themselves, if used). The only
thing is with this "cave" technology is that you might dig out some lube
and basic tools and fix it right there. A good thing with electronics
is that you might go a long time before needing a fix....it's all in
whats acceptable to YOU.

It sounds as if what you think you want could easily be much more
complex than what you're replacing (hopefully an engineer, ANYWHERE,
will read this and take heed!) Keep in mind the operating environment
for this circuit or problem as well....do you want anything that is
adjustable or prone to corrosion, immersion, high heat, extreme cold or
mechanical failure in this severe environment, considering the
consequences involved (you walking 20 miles home out of the bush for
example).

Just meant to be food for thought and to sure not deter you from your
pursuit - from someone who's been thar 'n done dat.


Gord

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Nick Hull
 
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Default $400 question; Igniter for ATV

In article , G
wrote:

There was a simpler (for us to see) way in the past....a mechanically
advanced "breaker plate" which originally mounted the points and later
perhaps just a pickup. For the manufacturer, what you have is likely
simpler. As it sounds like you got your igniter apart, is it repairable
(or was it a destructive process.....potted etc)? Most likely what you
have is a pretty simple circuit - why not reverse engineer it and either
repair what you have or build your own with similar but perhaps more
readily available components. Your cost to buy that unit has little to
do with the cost of its component parts and more to do with supply and
demand and typical lack of standardization.


Igniter was not potted, but the IC is covered with a secondary PC board
with surface mounted items so I can't read any numbers on the IC. It
might be repairable but I don't have a circuit diagram.

You mentioned a failsafe mode but then answered your own question by
noting that it might take extra circuitry to insert the delay (just one
possibility for failure). One such system used in the past was to
trigger the ignition coil (i.e. to be an igniter) via a capacitor
discharged using an SCR (CD ignition) - Timing voltage was picked up via
a coil being swept by a magnet on the flywheel (small engines). Advance
and retard were effected by nothing more than a simple RC circuit (fixed
time constant) which was overun as the engine sped up (capacitor didn't
have time to charge or delay the build up of the trigger for the SCR).


CD sounds like an interesting alternative, where could I get some info
on the design of the RC delay circuit. The board I have does not appear
to be CD since I see no big caps. I'm guessing the power device is
eother a transistor or a power mosfet (did they use power mosfets before
83?)

These types of modules often had nothing more than a few diodes, couple
of resistors and caps and of course the SCR. They MAY have used a
seperate supply coil (Dirt bike with no battery) which built system
voltage just before the ignition was required......this could have been
supplied by a battery as well though (as supplied by for cars and trucks).

With older mechanical technology you faced similar problems to what
you've experienced. The breaker plate (or perhaps just a moveable
breaker cam) could be "stuck" at some advance anywhere between low and
high speed (not to mention the points themselves, if used). The only
thing is with this "cave" technology is that you might dig out some lube
and basic tools and fix it right there. A good thing with electronics
is that you might go a long time before needing a fix....it's all in
whats acceptable to YOU.


I'd probably prefer ancient tech breaker points, I've fixed them many
times in the field, but in this case I don't have that option since
there is nowhere to put a breaker point. Of course I really want it
all, long life and ability to field repair or drive in the 'broken'
condition. I've driven a lot of broken stuff; cars and tractors with
broken steering, no clutch, no brakes, broken fuel system, etc.

It sounds as if what you think you want could easily be much more
complex than what you're replacing (hopefully an engineer, ANYWHERE,
will read this and take heed!) Keep in mind the operating environment
for this circuit or problem as well....do you want anything that is
adjustable or prone to corrosion, immersion, high heat, extreme cold or
mechanical failure in this severe environment, considering the
consequences involved (you walking 20 miles home out of the bush for
example).


This 3-wheeler almost never leaves my hundred acres and I can usually
tow it or carry it with my farm tractor. One of my principal uses is to
use the 3-wheeler to repair a broken tractor in the field, and the
tractor helps repair the 3-wheeler.

Just meant to be food for thought and to sure not deter you from your
pursuit - from someone who's been thar 'n done dat.


Gord


--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/


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G
 
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Default $400 question; Igniter for ATV

Howdy Nick......by your reply I can see that you know already most of
what I mentioned I don't recall power mosfets back that far but it's
possible. Wouldn't rule out that the device, especially if it's a
TO-220 or similar package isn't an SCR or similar either. I'll draw up
a schematic of an era CD box I unpotted and repaired for a Can-Am
motorcycle which is right at hand and shoot it off to you. The RC
circuit can basically be found in any basic electronics text book with
the formulas for finding instantaneous charged voltage etc....some
experimentation will be needed to find your offset though. There were
quite a few CD ignition kits around at one time and articles in various
electronic mags and project books so some digging there might be real
helpful.

Gord

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Nick Hull
 
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Default $400 question; Igniter for ATV

In article , G
wrote:

Howdy Nick......by your reply I can see that you know already most of
what I mentioned I don't recall power mosfets back that far but it's
possible. Wouldn't rule out that the device, especially if it's a
TO-220 or similar package isn't an SCR or similar either. I'll draw up
a schematic of an era CD box I unpotted and repaired for a Can-Am
motorcycle which is right at hand and shoot it off to you. The RC
circuit can basically be found in any basic electronics text book with
the formulas for finding instantaneous charged voltage etc....some
experimentation will be needed to find your offset though. There were
quite a few CD ignition kits around at one time and articles in various
electronic mags and project books so some digging there might be real
helpful.

Gord


CD sounds interesting but there are 2 questions; IIRC CD was sold as an
accessory to regular ignition points to take the current so the points
would not burn. The points were used to trigger the CD and the
mechanical spark advance was still used. This is all guessing from old
memories, I never used CD back then. I recall one of the arguments was
that if the electronics failed (as it did too often back then) the CD
system would revert to the regular points to keep the car running.

In addition to the mechanical advance, CD used a big cap to zap the
coil. Apparently I don't need the cap since my present system just
pulses the battery voltage.

If CD did use the mechanical spark advance it won't help me much. I
need to find a simple electronic spark delay, even if it is only a
simple fixed 30 deg delay, to pack for emergency use.

Ironically, I could really use CD for my tractor. It goes thru points
too fast, BUT it is 6-volt and positive ground and I have never seen a
CD for a 6-volt positive ground.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/
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Nick Hull
 
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Default $400 question; Igniter for ATV

In article ,
"ampdoc" wrote:

"Nick Hull" wrote in message
...
Between the flywheel pickup coil (magneto) and the high voltage coil for
the spark plug there is a black box that controls the spark and its
advance. This box on My Kawasaki 3-wheeler is called the Igniter and
this simple tiny circuit board costs $400! It was designed before 1982
and contains one IC and a bunch of discrete components. There has got
to be a better (cheaper) way to do this.

The spark starts at 10 deg before Top Dead Center and advances to 40 deg
before TDC by 2000 rpm. Since electronics cannot advance time
apparently the pickup is at 40 deg BTDC and the pulse is delayed to 10
deg BTDC at low speeds. If the timing delay fails the spark reverts to
40 deg BTDC for all speeds, meaning the engine cannot run at low speeds
therefore cannot be started. Bad idea.

How could this black box be designed using components availiable today
to control the spark advance, preferably adjustable or programable so it
would work in a wide variety of ATVs etc? If possible It would be
preferable to have the failure mode at low speed advance. Certainly I
would hope for a price below $400. All suggestions welcome

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/


I could see here the possibility of using a variable delay line and a
$14.00 4-wire GM ignition module say like form a late 1970's Monte Carlo,
Not sure how to make a delay line that would preserve the correct pulse
shape from the coil, however I am sure it is possible. One would rout the
signal from the pickup theu the delay to the amplifier module -- coil.
Having successfully used 4-wire GM modules to replace the two ignition
modules on a KZ-550LTD streetbike before because the spark amps from Kaw
were more expensive than the old bike, I am sure it will work, your only
problem being the timing advance, the KZ had mechanical advance.



The advance (delay) is the real problem because it is not constant in
time but must vary with crankshaft rpm even when a constant 10 deg BTDC
is needed at low speed. That's the part that has me puzzled.

--
Free men own guns, slaves don't
www.geocities.com/CapitolHill/5357/
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