Hi
I am putting together a second K2 so I have a 2nd RX set up. Does anyone know how to mute a K2? Thanks for any ideas 73, Bob G3PJT _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
----- Original Message ----- > > I am putting together a second K2 so I have a 2nd RX set up. Does anyone > know how to mute a K2? > --------------------------------------- Bob, A sledgehammer would do a permanent job of it <G> For something more temporary, an open collector transistor connected to pin 17 of the MCU (Control Board U6) would do the job for you - drive the base of the transistor with 3 to 5 volts to turn it on when you want the K2 muted. A 2N2222 or similar should work just fine. 73, Don W3FPR _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Ack! You sure you want to do this, Don? Pin 17 is bipolar drive, so you
would be shorting a relatively high-current output (25 mA per spec) to ground. That has a good potential for letting smoke out of the MCU. IF you do this, I HIGHLY recommend a current limiting protection resistor in the circuit. A few hundred ohms should do, but might also affect muting operation... On Dec 9, 2004, at 10:41 AM, W3FPR - Don Wilhelm wrote: > For something more temporary, an open collector transistor connected > to pin 17 of the MCU (Control Board U6) would do the job for you - > drive the base of the transistor with 3 to 5 volts to turn it on when > you want the K2 muted. A 2N2222 or similar should work just fine. -Jack Brindle, W6FB ======================================================================= _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
Jack,
It is not uncommon to 'wire-OR' bipolar devices. We commonly do that with other CMOS family devices which also spec a source/sink capability of 25 ma. or more. Yes, that is equivalent to shorting to ground with one of the devices at a logic high level. The sourcing spec for a bi-polar device tells me that is the max it can drive. I have not seen a limit on the 18C452 cumulative drive limit (number of outputs sourcing current simultaneously), so I don't believe that is any different than one output driving several loads for which the total current sourced would be a total of 25 ma. in the logic high state. The current comes from the equivalent of a collector resistor within the device itself. OTOH, Where overload usually occurs in bipolar devices is at Vol (when the device itself is holding a logic low level), when all attached devices (in sum) could cause greater than the I-sink rating to be conducted through the saturated output transistor - this usually results in a quick death. In a 'wire-or' application where only one of the driving devices contains the collector resistor, the sink current is not increased by adding another open collector driver, and for that reason, I did state that it should be an open collector driver. I admit I could not find detailed drive/sink information specific to the 18C452, and I am basing my conclusions on the specs for the remainder of the family. If you have information that differs, please let me know where to find it. 73, Don W3FPR ----- Original Message ----- > Ack! You sure you want to do this, Don? Pin 17 is bipolar drive, so you > would be shorting a relatively high-current output (25 mA per spec) to > ground. That has a good potential for letting smoke out of the MCU. > > IF you do this, I HIGHLY recommend a current limiting protection resistor > in the circuit. A few hundred ohms should do, but might also affect muting > operation... > > On Dec 9, 2004, at 10:41 AM, W3FPR - Don Wilhelm wrote: > >> For something more temporary, an open collector transistor connected to >> pin 17 of the MCU (Control Board U6) would do the job for you - drive the >> base of the transistor with 3 to 5 volts to turn it on when you want the >> K2 muted. A 2N2222 or similar should work just fine. > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
In reply to this post by Bob Whelan
Folks,
I had previously suggested a 'wire-OR' off pin 17 of the MCU to accomplish external muting for the K2. Jack Brindle pointed out that CMOS logic devices can be overloaded with such a 'wire-OR' configuration without a current limiting resistor. I have used many 'wire-OR' circuits with TTL logic, and since CMOS is "TTL compatible" (with a 5 volt Vdd supply), I erroneously extended the wire-OR solution to CMOS logic (in error). It turns out that in this particular case, a current limiting resistor is easy to add, and in fact, for this particular circuit, Wayne Burdick has previously suggested adding a series resistor of about 100k to slow down the K2 mute timing in order to reduce the audio pops that some have seen with the KDSP2 added. So if you wish to mute the K2 from an external source, you may still use the 'wire-OR' technique of attaching an open collector transistor to the gates of Q6 and Q7 on the Control Board (the 'hot' end of C23 is a good attachment point), but in addition, one should cut the trace from U6 pin 17 on the solder side of the Control Board and add a resistor between U6 pin 17 and C23. A value as low as 1k ohms will limit the current from the MCU to 5 ma or less (a safe value), while a value of 100k has been suggested by Wayne Burdick as a 'mute slow-down' for reducing the KDSP2 pop. So take your pick of values between these two to protect the CMOS MCU output from being overloaded when in its logic high state. Sorry for any confusion that I may have caused. 73, Don W3FPR _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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