Re: auto ignition coil: why autotransformer?
- From: don@xxxxxxxxxxxxxx (Don Klipstein)
- Date: Mon, 16 Oct 2006 23:02:51 +0000 (UTC)
In <Xns985E4CA7B4CDmeherenet@xxxxxxxxxxxxx>, me wrote (edited for space):
George <_g_bnotreallymyaddresseccles@xxxxxxxxxxx> wrote(I SNIP the alternative circuit as part of editing for space)
I want to use an old automotive ignition coil to generate a spark. I'm
puzzled that the (HV) secondary is connected to the primary. (I guess I
knew this, but I never gave it much thought before.) So, the spark
return current has to go through the battery and the harness:
________+12__________________
| | |
Batt PRI SEC
| | | (HV lead to distributor)
| | |
| POINTS SP PLUGS
|____Gnd______|_____________|
It seems it would make more sense to have an isolated secondary, with
one side connected to the coil's case. Then, the spark return current
could just go through the block back to the coil:
I must be missing something?
yes you are. The spark return is through the block since it is at ground
potential and so is one side of the coil....
I thought that usually neither end of the primary went to ground, but
one end did usually go to +12V (as shown in the above circuit that I
consider to be the traditional one, although omitted is the condenser in
parallel with the points.)
But out of 20,000 volts secondary voltage, how much difference does
12-14 volts make when we are eliminating a terminal and an external wire
connection? Especially since the secondary winding can be oriented for
that 12-14 volts to be adding to its EMF?
I think the main reason for making an ignition coil 3-terminal is to
save a terminal and an external connection. A few cents saved per car
adds up to a lot of money!
- Don Klipstein (don@xxxxxxxxx)
.
- References:
- auto ignition coil: why autotransformer?
- From: George
- Re: auto ignition coil: why autotransformer?
- From: me
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