Nuts and Volts

QUESTIONS & ANSWERS

best? What can I do to achieve a longer, bigger spark?

— Mike Wandishin

AI reproduced your circuit in Figure 7. The main problem I see is D4, which limits the flyback voltage.

The primary voltage needs to be free to go as high as necessary to allow the secondary to generate the spark. The snubber, R3 and C4, is a futile effort because the Jacob’s ladder is radiating and annoying the neighbors, anyway. The transistors should be rated 200 or 300 volts; if they blow up, go higher. R2 should be connected to the Q2 emitter — not to 12 volts — to protect the base-emitter junction of Q2. The higher the frequency, the better; as long as it does not exceed the self-resonant frequency of the coil.

■ FIGURE 7.

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