Electric Flight

摘要

This time, I want to define the operational limits of the Pico timer that I detailed in my last column and present a higher current design. I had a nice e-mail from George Pearce who came up with the concept a few years ago. His original timer used only a fixed resistor as small pots were unavailable then. He also used two nine-volt batteries in series to provide a higher Gate to Source voltage to turn on the MOS-FET. For any MOSFET there is a curve of Gate to Source voltage versus Drain to Source on resistance and a higher voltage reduces the on resistance.