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.

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. 

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