On Wed, 09 Jun 2004 18:35:33 GMT, "Vaughn Simon"
wrote:


"Ted Edwards" wrote in message
...
Vaughn wrote:

I don't think that those "electronic ignitions" for lawnmower
engines are
anything more than a hefty zener diode.

Now, why would a Zenner diode create the KV necessary for a spark?

It can act just like a set of points. It allows the voltage to rise to
a certain point, where it suddenly conducts, which collapses the magnetic
field. The collapsing field cuts the turns in the coil creating a spark. (I
think)


Got it backwards, kinda.
The votage increases, but there is no current until the zener fires.
The zener firing would BUILD the magnetic field, not collapse it.
Might still work if the field could build as fast as opening points
allows it to collapse. But some how you need to collapse that feild
too - which MAY happen effectively when the zener stops conducting.
Only problem is, the coil "rings" and the zener would likely false
trigger, killing the spark prematurely.

I suspect there is something a bit fancier than a Zener in the little
box.
I run a communications shop and we have drawers full of parts, some
of
which would likely do the job just fine.

Do you use Zenner diodes for RF generation too?

Used mostly in DC power supply circuits and in circuit protection, come
in many voltages and physical sizes depending on power.

Vaughn



Ted