Alex, It certainly is, but most circuits using a single pole single throw switch (normal key contacts) suffer from the same difficulties as the K2 key input circuits - one must make some assumption about the duration of the bounce and decide if it is a valid key closure or not. To do it in a foolproof manner requires a SPDT switch, and the closure of the NO contact sets a latch, the closure of the NC closed contact resets it - simple set/reset latch, no clocking required.
So if one were willing to swap their favorite hand-key for one with a SPDT set of contacts, it would work flawlessly - perhaps someone else will come up with a better method, but that is the circuit that I have used for de-bouncing when complete assurance of a contact closure is required. Noise on the set contacts may get through, but will not set the latch because the reset contacts are still closed. A couple of 2 input NAND logic gates and a couple of inverters will do the job nicely. In the meantime, I will use an external keyer and leave the K2 set to INP Hand to accomplish the same task - the K1EL K12 keyer is small, can run a long time from a coin battery and does the job for me. I am not knocking the K2 keyer, but I am getting used to my K1EL keyer and I can use it with any rig with no time to become accustomed to a particular internal keyer. 73, Don W3FPR > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf Of Alexandra Carter > Sent: Sunday, February 05, 2006 8:04 PM > To: [EMAIL PROTECTED] > Cc: [email protected] > Subject: Re: [Elecraft] K2 dual keying problem > > > Is is possible to add a de-bounce circuit to the hand key? 73 de Alex > NS6Y > > On Feb 5, 2006, at 5:41 AM, Don Wilhelm wrote: > > > David, > > > > I would rather speculate that it is a uP timing situation coupled with > > contact bounce at the key and the forward voltage drop of the diodes. > > If > > one of the diodes is a bit slower than the other, the voltage seen at > > the uP > > pins may actually look like one pin has gone to a low state before the > > other > > (that is the condition to generate the iambic alternating dots and > > dashes). > > This problem can be caused by contact bounce at the hand key - > > cleaning the > > hand key contacts will help, but one can never cure contact bounce at a > > mechanical closure point. > > > > The net of the story is that the uP must believe that both the dot and > > dash > > contact closures occurred together, and the only way that can be known > > is > > for it to sense a low voltage on both its input pins. If the polling > > of > > those pins happens to occur during a contact bounce period and one of > > the > > diodes is a bit slower than the other it will appear to the > > microprocessor > > that only one of the contacts was closed. > > > > I am surprised that two diodes in series appears to work better - in > > fact it > > will make the low state at the uP pins at an even higher voltage than > > one > > diode. I would suggest that you try using Shottky diodes (like 1N5711) > > instead to lower the voltage at the uP pins when the hand key is > > closed. > > > > So clean your key contacts and go back to one diode for each side and > > if > > still a problem switch to Schottky diodes. > > > > 73, > > Don W3FPR > > > >> -----Original Message----- > > > >> > >> Mindful that I am neglecting my hand keying, my sending being spoilt > >> by > >> the ease of using an iambic paddle, I have connected a straight key > >> across the paddle keying line using a pair of 1N4148 diodes as shown > >> in > >> the K2 Manual. This works reasonably well, but occasionally when > >> pressing the straight key I get a string of alternate dots and dashes. > >> > >> I presume that the problem is caused by the reverse resistance of the > >> diodes being too low. I tried putting two 1N4148 diodes in series in > >> both lines. This is better but has not cured the problem completely. > >> Has > >> anyone else had this problem? Or does anyone have a suggestion as to > >> how > >> both a paddle and straight key may both be connected to the K2 with > >> reliable results. > >> > >> 73 de David G4DMP > >> > >> > > > > _______________________________________________ > > Elecraft mailing list > > Post to: [email protected] > > 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 > > > > _______________________________________________ > Elecraft mailing list > Post to: [email protected] > 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 > > > -- > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.1.375 / Virus Database: 267.15.2/251 - Release Date: 2/4/2006 > > _______________________________________________ Elecraft mailing list Post to: [email protected] 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
