When the relay solenoid's magnetic field collapses when power is removed it will produce a sizeable reverse-polarity surge at the 12V connector. A diode across the leads oriented to it is normally reverse polarity (anode to ground, cathode to +) will conduct when that surge occurs and keep most of it from reaching the K3.
Depending upon the inductance of the solenoid that surge can be quite large, producing many times the 12 V that was applied with rather large current for a brief interval. It's important to choose a diode that can handle those surges without failing. Power supply diodes are a good bet for a fairly heavy duty relay. Ron AC7AC -----Original Message----- Now that's a good idea. Why the diode? 73 de M0XDF, K3 #174 -- On 14 Nov 2009, at 08:31, AD6XY wrote: > My K3 12V output powers an automotive relay (+diode) which connects > the 12V > PSU to an 8 way powerpole panel. This allows me to control the power > to the > LP-100A, the transverters, the KRC2 and an AT-1000pro with the K3 > power > switch. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
