Paddle
Processor - Debouncer
Now
available!
It appears that some of the new
paddle designs have abandoned the time tested coin silver contacts and are using
"improved" alloys in an attempt to avoid problems with oxidation and
corrosion.
While those alloys and/or surface treatments seem to be reliable when used in
circuits with a high threshold separating "key up" and "key down"
states, the new contacts are a problem with PIC based keyers like WinKey that use
a voltage divider and single input pin to sense both the "dit" and
"dah" paddle closure and some "low power" (3.3 volt CMOS)
keyer designs.
These new alloys appear to create
a semiconductor rather than conductive contact. In trying to discover the
source of the incompatibility between some of the newer paddle designs and WinKey, it appears
that the voltage drop across the paddle contacts is essentially independent of the
current through the contacts. In one test, the divider resistors in the WinKey
input network were scaled by a factor of 10 in an attempt to make contact resistance
a smaller part of overall circuit resistance ... with absolutely no difference in
behavior! This surprising response is exactly what would be predicted if the
contacts were acting like a forward biased diode.
To accommodate these new paddle
designs, K1EL and microHAM have cooperated to produce a "paddle processor/debouncer."
The debouncer uses a micropower PIC with independent, high threshold inputs to sense the
paddle state. Paddle closures are processed with an advanced debouncing algorithm
to remove all "noise" on the inputs and passed on to the keyer as unambiguous
levels.
The debouncer consumes less than
1 mA in operation and about 1 uA in sleep mode. It will operate for
several years on the internal "coin" battery without the need for
a power switch.
The debouncer is available in two versions. Both
versions have 20 cm output cables terminated in a standard 1/4" stereo
plug to connect to microKEYER or CW Keyer. The Begali version
has a one meter long input cable which terminates in a 3.5 mm (1/8")
stereo plug which will connect directly to the paddles. The generic
version replaces the 3.5 mm plug with a 1/4" stereo jack.
Copyright � 2008 - microHAM America, LLC
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