“In the November 1999 issue of EPE (Everyday Practical Electronics), a small and intriguing circuit was published in the Ingenuity Unlimited section by Z. Kaparnik. It was a very small implementation of a typical transformer feedback single transistor invertor. The transformer was a standard ferrite bead with two windings wound on it and the circuit was using the high voltage pulse generated when the transistor turns off to light an LED from a single 1.5V battery. This page has two variations on the original design to use the simple circuit in a useful manner.” Link.
4 thoughts on “HOW TO – Make a Joule thief”
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While it might be overkill, you could use the CF Sound II. It’s a CompactFlash-based audio player that has a couple of pushbutton inputs that you could use for the front and back doorbell buttons. These are the audio players that are often used in the homebrew R2-D2s that were featured in MAKE:
Of course, the next step in the project is to add a fingerprint reader to the doorbell button and play different sounds depending on who is knocking.