Chris,
The maximum keying current required by the K2 is limited by the 5 volt
sourced by the MCU input and its pullup resistors. There is a 220 ohm
resistor in series with the signal line - so the maximum current will be
23 ma. Most any garden variety NPN transistor will do the job for you.
73,
Don W3FPR
Chris Kantarjiev wrote:
I'd like to build a parallel port keying cable for my K2. Lots of schematics
on the web, all calling for a 2N2222. I find that I don't have any of
those in my junk box right now (horrors!) but have lots of 2N4124;
the big difference is that the 4124 is limited to 200mA collector current.
It seems like this should be enough, since the keyer contact goes
straight to the MCU ... right?
73 de chris K6DBG
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