And, YES, pin 15 is the ground, (-) of the 12 volt supply.
Dave, The pin 8 diode connection should go to the (+) side of the power supply which in your description is also the bottom of the ice cube coil. The top of the coil goes to pin 7. This puts a diode across the coil with its cathode to the (+) side and the anode to the (-) side of the coil when it is energized. ie the pin 7 output is on or low. The ULA2003 chip has the 7 outputs connected to pins 1-7 on the X2 connector. The chip also has protection diodes with each anode connected to each pin and the cathodes are all tied together and run to pin 8. The diodes do nothing in the off position and nothing in the on position either. But, when the transistor switch opens, going from on to off, there is a reverse voltage created across the relay coil by the collapsing magnetic field of the relay coil that can be several hundred volts for a few microseconds. This reverse voltage is enough to toast the transistor switch because it greatly exceeds the breakdown voltage rating (Vds I think) of the transistor. During this reverse voltage spike the diode conducts, thus limiting the voltage to a volt or so which gives us the happy ending to our tale. Now, if you are also using other relays to switch transverters or antennae from pins 1-6 then those relays have to be run from the same supply, 12 volts in your case. This is because of the common connection pin 8 of the protection diodes in the ULA2003. I put a separate 1N4006 back diode across each relay in my amps and use an isolator board for each output so I minimize the risk of toasting the ULA2003 chip. I don't use the pin 8 connection at all. The isolator board is N0XAS Universal Keying Adapter II.< www.hamgadgets.com > MFJ sells the ARB-704 Amplifier Interface Buffer keying box but I have no experience with it. 73, Larry K2LT Dave Muskopf wrote: > This is confusing to me. My kw's big 112 volt ac clapper relay is keyed > by an ice cube relay (12volt dc at apx 50ma.). The (+) lead from the 12 > volt supply goes to the bottom of the ice cube relay coil. The (-) lead > from the supply is grounded. I key the kw by shorting the top lead from > the ice cube relay coil to ground. (Sounds like a galloping horse on cw) > Now, are you saying I should connect the top lead of the relay coil (+) > to pin 8 of x2 and the ground lead (-) from the supply to pin 15? W8XO > > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz > Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ > FlexRadio Homepage: http://www.flex-radio.com > > > _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Homepage: http://www.flex-radio.com
