This can work. But it can cause problems as well. You should add isolation in the form of either small diodes (cathode towards K3) or small resistors (maybe 100 ohms). The problem is that if the Arduino is left powered on when the K3 is off, the Arduino can actually leak power into the K3 through these connections and can actually power parts of the K3 (as in parts, but not all, of the cpu). This false power can lead to other problems, which is why we suggest the isolation diodes.
The second thing is to remember that 60 meters is coded as all zeros. The K3 has pullup resistors on the band lines, which will pull the band lines to whatever Vcc happens to be at that time. When the K3 is off, Vcc is zero, which will be the value of the band lines (i.e. not high-impedance). Thus when the K3 is off, you will see a band selection of 60 meters. KPA500 users see this as the KPA500 switches to 60 meters if it is left powered up after the K3 is switched off. Good luck with the project! - Jack, W6FB > On Feb 7, 2016, at 9:47 AM, Bill Frantz <[email protected]> wrote: > > I have built a similar switch controller. If anyone wants a copy of the > details, please ask. > > Specifically: > > - Just connect te band lines directly to the Arduino inputs. It works fine. > > - Don't know about cross band split. However K 3 power off and 60M look the > same. > > - I don't bother. I don't change bands while transmitting. I'm not sure if > the K3 even supports it. > > 73 Bill AE6JV > > > On 2/7/16 at 3:38 AM, [email protected] (Pierfrancesco Caci) wrote: > >> Hello, >> I'm trying to make my own interface between the band data lines on the >> accessory connector of the K3 and the remote antenna switch. >> I have a few questions that I hope you can help me with: >> >> - is it safe to just poll the band lines with the arduino digital input >> pins? I understand that my K3 is new enough to have the internal pull >> up resistor. Should I put an isolation device inbetween? >> >> - does the band data as provided by the K3 always track the TX VFO? >> Should I expect some weird situation if I ever try to do cross-band >> split? >> >> - should I bother with asserting TX Inhibit and keep it set for a few >> milliseconds when I detect a band switch? > > ----------------------------------------------------------------------- > Bill Frantz | I don't have high-speed | Periwinkle > (408)356-8506 | internet. I have DSL. | 16345 Englewood Ave > www.pwpconsult.com | | Los Gatos, CA 95032 > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [email protected] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
