Touch Sensor Iambic

This is a touch paddle is based on an article by Tony Urbizu, WB4TED, which was published originally in the January 1978 73 Amateur Radio magazine. It was subsequently reprinted in the April 2000 73 Amateur Radio Today magazine. The design uses two 2N2222s in a Darlington configuration for the dot side, and an identical circuit for the dash side.

The current gain for a Darlington pair is the product of the HFE of each transistor. With a typical HFE of 200, this circuit has a gain of ~40,000. Which allows it to perform as a touch switch. Here is Tony's original article. I feel safe including it here since the magazine ceased publication in October 2003.

In April 2007 I wrote an article entitled "Evolution of a Finger tapper" for the now defunct Iowa QRP Club's Journal, In it I chronicled the steps WAMWW, WBFGB, and I followed to reach a usable finger tapper paddle. Along the way we had fun and played with several different touch paddle designs, the TouchPad being one of them. It is in two parts, here is part one and part two in PDF files. The Journal was edited and published by Walter Dufrain, K5EST. Walter is a fine editor/publisher as you will see. Here is a an HTML copy of the article it loads much faster than the PDFs.

Revised 2 Dec 2012
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