A better solution
After my "Smoke Generator" article was published in the newsletter, Alan Bond contacted me to suggest that if a power surge during switch on is a problem, a much better solution than my use of potentiometers is to use "negative temperature coefficient (NTC) thermistors". These are connected in series with the load. At switch on the thermistor is cold and therefore it has a high resistance which limits the current. Then as the current flows, the high resistance causes the thermistor to heat up, its resistance then drops and very nearly the full voltage is applied to the circuit. Alan can supply more details of part numbers and source if you want to use this technique.
Peter Taylor
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