Preventing damage to my Basic Stamp

RichardF

I want to experiment with generating high voltage arcs/spark using the BS2 as a controller. Basically, I will connect an output pin to the primary of an automobile ignition coil in series with a 220 ohm resistor and pulse the coil the same as in an auto ignition. I can experiment with differnet pulse widths and frequencies. I am concerned about counter emf from the collapsing secondary winding field zapping the BS2. I could hook a diode across the secondary to short circuit the reverse current, but I don't know of any diodes that can withstand the·high voltage·generated by an ignition coil.
Thanks for the help.
Richard

Bill Chennault

Richard--

Like you, I am a newbie. However, all you are going to get out of the Stamp's output pin is five volts. More importantly, you will get MILLIAMPS, not amps! There needs to be more involved than a 220 ohm resistor. I am sure an expert will chime in, but I am thinking you need a very fast solid state relay to switch the amperage at the·12 volts you need to drive that coil.

Good luck and what kind of project is it?

--Bill

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You are what you write.

GICU812

There is no way a stamp could drive an ignition coil. Your best bet for it to work, and for isolation, is to use a transistor to drive a relay, which in turn activates the coil.

Mike Green

An optoisolator would provide the protection needed and can be driven directly from a Stamp I/O pin (since it's just an LED from that side). The output side of the optoisolator is just a phototransistor which could drive another (power) transistor to switch the 12V for the ignition coil much like an electronic ignition system. You will need a reverse connected diode across the ignition coil primary to protect this power transistor, but the back EMF from the primary is not that high. An ordinary 50V rectifier like a 1N4001 is more than adequate in a 12V primary circuit.

Bill Chennault

Mike--

Gee. How about that FuturLec SSR you recommended to me to switch 24 amps at 12 volts? Might it be too slow? Your reply to his post kinda sounds like a description of the SSR.

By the way, their shipping is SLOW. Still waiting. I will probably call or e in two days.

Thank you again for the recommendation.

--Bill

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You are what you write.

Dgswaner

have you considered using a Neon sign transformer? they are commonly used for Jacobs ladders and "lifter technology" experiments. I think you would find it easier to modify one of these units rather than a Ignition coil.

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A complex design is the sign of an inferior designer. - Jamie Hyneman, Myth Buster