I also added a 1n4148 diode across the relay coil to absorb the back EMF when the relay opens. Probably not needed, but it seemed like cheap protection.
Tuesday, March 31, 2009
Schematic for the Step-start
Dennis N2RIT wrote to ask me about the schematic for the Step-start circuit. Well, Dennis, it's pretty simple. I used the design posted by Rich Measures AG6K here. For the AL-80A, I used the +12 volt supply, which is about 15 volts unregulated. The coil of the relay I used is about 360 ohms, so to get the voltage about right, I used a 100 ohm dropping resistor.