K3 band data lines
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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? Thanks Pf -- Pierfrancesco Caci, ik5pvx ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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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, [hidden email] (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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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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 <[hidden email]> 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, [hidden email] (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:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Bill Frantz
Thanks Bill. My point about the tx inhibit was that I plan to have a "manual selection" button, and I was thinking that maybe it would be nice to have a "fool avoidance" built in. The fool being me, of course. Pf >>>>> "Bill" == Bill Frantz <[hidden email]> writes: Bill> I have built a similar switch controller. If anyone wants a copy of the details, please ask. Bill> Specifically: Bill> - Just connect te band lines directly to the Arduino inputs. It works fine. Bill> - Don't know about cross band split. However K 3 power off and 60M look the same. Bill> - I don't bother. I don't change bands while transmitting. I'm not sure if the K3 even supports it. Bill> 73 Bill AE6JV Bill> On 2/7/16 at 3:38 AM, [hidden email] (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> ----------------------------------------------------------------------- Bill> Bill Frantz | I don't have high-speed | Periwinkle Bill> (408)356-8506 | internet. I have DSL. | 16345 Englewood Ave Bill> www.pwpconsult.com | | Los Gatos, CA 95032 -- Pierfrancesco Caci, ik5pvx ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Jack Brindle-2
The band input line pins are set up as input on the Arduino. As
such, they are high impedance, so I don't think there is any way to drive them from the Arduino (short of changing the program/sketch). I normally leave my switch controller powered on with the K3 powered off, and have not experienced any problems. If there were other things in the shack driving the lines, there might be a over voltage issue for the Arduino, but I think there would also be issues with the K3 driver circuitry. (One drives high, one drives low and lots of current flows.) 73 Bill AE6JV On 2/7/16 at 10:52 AM, [hidden email] (Jack Brindle) wrote: >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 <[hidden email]> 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, [hidden email] (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:[hidden email] >> >>This list hosted by: http://www.qsl.net >>Please help support this email list: http://www.qsl.net/donate.html >>Message delivered to [hidden email] > > Bill Frantz | If you want total security, go to prison. There you're 408-356-8506 | fed, clothed, given medical care and so on. The only www.pwpconsult.com | thing lacking is freedom. - Dwight D. Eisenhower ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I've done an experiment. I got a 7805 and powered it from a separate power supply. The negative of the 7805 is connected to the GND of the arduino. If I connect the 5V from the 7805 to one of the digital inputs, the arduino powers up and executes my program, lighting up the leds as expected. If I add the diodes as suggested by Jack, this doesn't happen anymore. But I can't read the 5V from those lines anymore, either. I'm now trying to figure out how to replicate the BAND line driver circuit that is mentioned on Cady's book on my breadboard. Not sure if I can simulate the mosfet by just shorting that line to ground between the 2.2k and the 220 ohm resistors. In any case, in this configuration I have to use the arduino internal pullups, and if I disconnect the external 5V power, I still measure around 1.3 V in the place where there would be the K3's 5V, if I have the arduino still powered up. Also, the logic signal of the lines seems to be reversed. I'm seriously thinking that the safest way for me to proceed at this point would be an optoisolator. Pf >>>>> "Bill" == Bill Frantz <[hidden email]> writes: Bill> The band input line pins are set up as input on the Arduino. As such, Bill> they are high impedance, so I don't think there is any way to drive Bill> them from the Arduino (short of changing the program/sketch). I Bill> normally leave my switch controller powered on with the K3 powered Bill> off, and have not experienced any problems. Bill> If there were other things in the shack driving the lines, there might Bill> be a over voltage issue for the Arduino, but I think there would also Bill> be issues with the K3 driver circuitry. (One drives high, one drives Bill> low and lots of current flows.) Bill> 73 Bill AE6JV Bill> On 2/7/16 at 10:52 AM, [hidden email] (Jack Brindle) wrote: >> 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 <[hidden email]> 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, [hidden email] (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:[hidden email] >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >>> Message delivered to [hidden email] >> >> Bill> --------------------------------------------------------------------------- Bill> Bill Frantz | If you want total security, go to prison. There Bill> you're Bill> 408-356-8506 | fed, clothed, given medical care and so on. The Bill> only Bill> www.pwpconsult.com | thing lacking is freedom. - Dwight D. Eisenhower -- Pierfrancesco Caci, ik5pvx ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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The opto isn’t needed. Just a low-voltage-drop diode (1N5711 should work) with cathode towards the K3, pullup resistor (47K to 100K) to +5V (or whatever the Arduino runs on, might be 3.3V), then the Arduino input pin. This will protect the Arduino from being falsely powered from the K3.
This is standard design for devices that are separately powered (think hot swap systems) in order to keep the unpowered one from being falsely powered by the one that is turned on. In other words it will keep the K3 from falsely powering the Arduino through the IO pin. The real problem with this is that if the device is powered in this fashion it can actually latch up part (or all) of the chip, damaging it. Adding a diode and pullup resistor (or even using the internal pullup in the Arduino if it has one) is very cheap protection for this scenario. This is something that surprises everyone the first time they see it. It is easily handled once you know what is going on. The pullup resistors were added sometime after the K3 shipped in order to help external devices that don’t have their own pullup resistors. It is not surprising that they do not appear on early schematics, but they are on current schematics. The circuit shows a 2.2K ohm pullup to +5V followed by a 220 ohm series resistor. This will deliver about 2.2mA of current to the IO pin, enough to power some micro controllers. Thus the need for the protection circuit. - Jack, W6FB > On Feb 8, 2016, at 12:48 PM, Pierfrancesco Caci <[hidden email]> wrote: > > > I've done an experiment. > I got a 7805 and powered it from a separate power supply. > The negative of the 7805 is connected to the GND of the arduino. > If I connect the 5V from the 7805 to one of the digital inputs, the > arduino powers up and executes my program, lighting up the leds as > expected. If I add the diodes as suggested by Jack, this doesn't happen > anymore. But I can't read the 5V from those lines anymore, either. > > I'm now trying to figure out how to replicate the BAND line driver > circuit that is mentioned on Cady's book on my breadboard. Not sure if I > can simulate the mosfet by just shorting that line to ground between the > 2.2k and the 220 ohm resistors. In any case, in this configuration I > have to use the arduino internal pullups, and if I disconnect the > external 5V power, I still measure around 1.3 V in the place where there > would be the K3's 5V, if I have the arduino still powered up. > Also, the logic signal of the lines seems to be reversed. > > I'm seriously thinking that the safest way for me to proceed at this > point would be an optoisolator. > > Pf > > >>>>>> "Bill" == Bill Frantz <[hidden email]> writes: > > > Bill> The band input line pins are set up as input on the Arduino. As such, > Bill> they are high impedance, so I don't think there is any way to drive > Bill> them from the Arduino (short of changing the program/sketch). I > Bill> normally leave my switch controller powered on with the K3 powered > Bill> off, and have not experienced any problems. > > Bill> If there were other things in the shack driving the lines, there might > Bill> be a over voltage issue for the Arduino, but I think there would also > Bill> be issues with the K3 driver circuitry. (One drives high, one drives > Bill> low and lots of current flows.) > > Bill> 73 Bill AE6JV > > Bill> On 2/7/16 at 10:52 AM, [hidden email] (Jack Brindle) wrote: > >>> 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 <[hidden email]> 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, [hidden email] (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:[hidden email] >>>> >>>> This list hosted by: http://www.qsl.net >>>> Please help support this email list: http://www.qsl.net/donate.html >>>> Message delivered to [hidden email] >>> >>> > Bill> --------------------------------------------------------------------------- > Bill> Bill Frantz | If you want total security, go to prison. There > Bill> you're > Bill> 408-356-8506 | fed, clothed, given medical care and so on. The > Bill> only > Bill> www.pwpconsult.com | thing lacking is freedom. - Dwight D. Eisenhower > > > -- > Pierfrancesco Caci, ik5pvx ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by Pierfrancesco Caci
I'm not familiar with Arduino circuit details, however... logic inputs
typically have a clamp diode to Vcc. So, if you are applying 5V to an input without powering the circuit, in other words, Vcc=0, then you are forward biasing the protection diode. This is very likely what is powering the Arduino via an input port. That's bad because the internal clamp diodes are not designed to conduct much current and you risk damaging the part. Once you understand and look at the actual input circuit and driving output circuit, you'll know if this is something that needs to be fixed. For example, pushing a small current through the diodes when Arduino is unpowered may be fine. Or a series resistor on the input to limit the current. The problem you see with your test may not be relevant since the K3 output line can't source current like a 5V supply. I saw Jack is suggesting a diode, with cathode toward the K3 output port. This is allowing the K3 to pull-down the Arduino input, but not pull it up. That may explain why you can't read the port with the diodes in place. Assuming inputs are directly connected to the Arduino's ATMega processor, you need to make sure the internal pull-ups are enabled in the processor. You can directly measure the port voltage with a DVM to see if they are being pulled up as needed. Sorry for some ignorant conjecture about circuits I haven't looked at, hopefully it's of some use! 73, Josh W6XU On 2/8/2016 12:48 PM, Pierfrancesco Caci wrote: > I've done an experiment. > I got a 7805 and powered it from a separate power supply. > The negative of the 7805 is connected to the GND of the arduino. > If I connect the 5V from the 7805 to one of the digital inputs, the > arduino powers up and executes my program, lighting up the leds as > expected. If I add the diodes as suggested by Jack, this doesn't happen > anymore. But I can't read the 5V from those lines anymore, either. > > I'm now trying to figure out how to replicate the BAND line driver > circuit that is mentioned on Cady's book on my breadboard. Not sure if I > can simulate the mosfet by just shorting that line to ground between the > 2.2k and the 220 ohm resistors. In any case, in this configuration I > have to use the arduino internal pullups, and if I disconnect the > external 5V power, I still measure around 1.3 V in the place where there > would be the K3's 5V, if I have the arduino still powered up. > Also, the logic signal of the lines seems to be reversed. > > I'm seriously thinking that the safest way for me to proceed at this > point would be an optoisolator. > > Pf > > >>>>>> "Bill" == Bill Frantz <[hidden email]> writes: > > Bill> The band input line pins are set up as input on the Arduino. As such, > Bill> they are high impedance, so I don't think there is any way to drive > Bill> them from the Arduino (short of changing the program/sketch). I > Bill> normally leave my switch controller powered on with the K3 powered > Bill> off, and have not experienced any problems. > > Bill> If there were other things in the shack driving the lines, there might > Bill> be a over voltage issue for the Arduino, but I think there would also > Bill> be issues with the K3 driver circuitry. (One drives high, one drives > Bill> low and lots of current flows.) > > Bill> 73 Bill AE6JV > > Bill> On 2/7/16 at 10:52 AM, [hidden email] (Jack Brindle) wrote: > > >> 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 <[hidden email]> 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, [hidden email] (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:[hidden email] > >>> > >>> This list hosted by: http://www.qsl.net > >>> Please help support this email list: http://www.qsl.net/donate.html > >>> Message delivered to [hidden email] > >> > >> > Bill> --------------------------------------------------------------------------- > Bill> Bill Frantz | If you want total security, go to prison. There > Bill> you're > Bill> 408-356-8506 | fed, clothed, given medical care and so on. The > Bill> only > Bill> www.pwpconsult.com | thing lacking is freedom. - Dwight D. Eisenhower > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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