+++++++++++++++++ Date: Fri, 24 Jan 2003 16:21:44 -0600 To: , From: Tom Hammond Subject: Re: [Elecraft] The state of a latching relay Sverre: >If I understand right, the latching relays in the K1 and K2 change state >every time you give them current for a short while, and then stay in the >new position until the next impulse is given to them. To my mind this >makes it impossible to figure out which position they are in, but I'm >probably missing something here. > >So the question to the clever ones is: How does the firmware in the K's >know the relay settings? 1) It remembers what band you're on and which relays should be reset for that band. It may 'cycle' all relays upon turn-on as well, and then reset them to the last band. 2) The relays only change state if they are given the correct POLARITY signal as well... one polarity SETs and the other RESETs. 3) Since the relays DO latch, if you select a band and then turn the radio off, the relay will remain in the appropriate state for that band. So you can then use an ohmmeter to perform a continuity test on the relay contacts to verify that it really is SET (or RESET). 73, Tom N0SS +++++++++++++++++ Date: Fri, 24 Jan 2003 18:23:15 -0800 (PST) From: Jessie Oberreuter To: Sverre Holm - LA3ZA Cc: elecraft at mailman.qth.net Subject: Re: [Elecraft] The state of a latching relay Current in one direction latches one state -- opposite in the other. The relays are biased against a cap, so as long as you apply a logical voltage for a period long enough to charge/discharge the cap, as soon as you switch the logic state, a potential will exist between a gate input/output and cap that are at opposite potentials. The relay will follow. If you flash them all on then off, you will have established known state and charge and you can then change any one at will. On Fri, 24 Jan 2003, Sverre Holm - LA3ZA wrote: > If I understand right, the latching relays in the K1 and K2 change state > every time you give them current for a short while, and then stay in the > new position until the next impulse is given to them. To my mind this > makes it impossible to figure out which position they are in, but I'm > probably missing something here. +++++++++++++++++ From: "Don Brown" To: , Subject: Re: [Elecraft] The state of a latching relay Date: Fri, 24 Jan 2003 21:22:59 -0600 Hi This some more of that firmware magic I was talking about. Notice one side of all of the relays are connected together. The other side of each relay is connected to an output pin on the IO controller. These pins can source or sink current. Now if you make all of the pins low except the relay you want to switch this will place a voltage in say, polarity + across the relay and will set it. Now if you want to switch the relay to the reset condition then you make all of the pins high except the relay you want to reset. Now you have a - polarity across the relay and that relay resets. This sequence can be repeated as many times as required and very quickly. Once the relays are in the proper position they mechanically hold their condition so no further power is needed to hold them and all of the pins can be set high or low. Then no current will flow because there is not a difference of potential. Only the relay that you want to switch will switch because all of the other relay coils are in parallel so only a small amount(1/18 if you have the 160 module) of current flows in each coil except the one you want to switch and it get the full current pulse. Don Brown KD5NDB ----- Original Message ----- From: "Sverre Holm - LA3ZA" To: Sent: Friday, January 24, 2003 3:44 PM Subject: [Elecraft] The state of a latching relay > If I understand right, the latching relays in the K1 and K2 change state > every time you give them current for a short while, and then stay in the > new position until the next impulse is given to them. To my mind this > makes it impossible to figure out which position they are in, but I'm > probably missing something here. > > So the question to the clever ones is: How does the firmware in the K's > know the relay settings? > > 73 > > Sverre Holm, LA3ZA > ------------------ > www.qsl.net/la3za ++++++++++++++++