Unofficial FAQ: Ignition corrections

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Michael Pardee wrote:


the "blurring" is diffusion - the operating temp doesn't even get close to melting - but diffusion is powerful stuff and it definitely destroys semiconductors.

the two factors at play are temperature & time. if the device was physically big enough and you solderd quick enough, there's no reason you couldn't do it - afterall, what temperature does a silcon foundry work at? but you got to be /quick/ if you go to high temps. or best not at all if you want good service life.

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Even the best heat sink does not conduct all the heat away from a semiconductor junction.The semi junction temp increase is probably faster than what the HS can conduct away,and having a higher base temp would make that occur faster.
--
Jim Yanik
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One more update: http://www.tegger.com/hondafaq/igniter-operation/index.html
This has been a most interesting thread, I must say.
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TeGGeR

The Unofficial Honda/Acura FAQ
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Looks good!

"flyback" voltage;when the coil is charged,the magnetic field builds up,then when the charging current is removed,the collapsing magnetic field generates a voltage in the opposite direction of the charging current.
The flyback voltage IS the HV pulse that the spark plugs get.
The mag field is generated by the primary,12V side of the coil,but the collapsing magnetic field induces the flyback pulse in both the primary and secondary of the coil,that's how the HIGH voltage is generated;the secondary has many more turns of a finer wire(finer to fit more turns in the same space);more turns,the higher the voltage induced.In the automotive ignition coil,the primary is connected to the secondary,and the HV current also travels through the primary.
That is why there's a bypass diode,it shunts the flyback current around the Darlington,to keep it from breaking it down from over-voltage.It's part of the path for the flyback voltage.
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Jim Yanik
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