A Few thoughts on the Bug Descratcher III kit

 The Bug Descratcher III kit:

http://wb9kzy.com/bugde3.htm

remains a consistent seller.  I added an enclosure kit last year using an aluminum or fiberglass circuit board as the top on a phenolic box.

The kit idea came from a Hint and Kink in QST by Dave Cuthbert, WX7G.  The first two versions were done with hardware (although different from the WX7G circuit) but on the third version I changed to a PIC microprocessor.

The design goals for the third version were to make it as bulletproof as possible so the LM2936 regulator was used along with a PN2222 output transistor to make the kit more resistant to static damage, polarity reversals and so on.

In addition, no elaborate software debouncing was used.  Instead a simple RC hardware based approach was used.  The PIC wakes up when the key input goes low and turns the output transistor ON.  Then the PIC ignores the input for a time "programmed" by the external RC circuit of R4+R5 and C5.  The values in the kit result in an approximate 12.5 mS delay where any contact bounce is ignored.  

The PIC then starts looking at the input for a key-up condition.  When key-up is detected the output transistor is turned OFF and the input is again ignored for about 12.5 mS.

Here is a scratchy dit as recorded by a customer:

The dit is being sent about 20 WPM with roughly a 60 mS key up/down time.  Unfortunately the contacts on this particular bug are bouncing past the intial debounce period so the Bug Descratcher III has kerchunked in a key up delay.  One possible complicating factor is the rig being used, modern rigs may do their own debouncing internally.

I advised the customer to increase the values of R4/R5 or C5 to increase the debounce time - hopefully that will fix the problem.

Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm