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RE: Controlling 28V relays

The scheme I use is to use a real 24 VDC supply. I use a series resistor for
each relay sized so that the relay will hold in after it has been energized.
The I parallel the resistor with a large electrolytic capacitor to give the
relay an extra current "jolt" when it is energized. This is probably the
minimum number of parts solution.

It has worked especially well with Transco "Y" solenoid operated relays
which tend to run pretty warm when hit with a full 24/28 volts. The series
resistor is typically about 1/2 of the DC resistance of the coils, and the
shunt capacitor is usually ~5000 uf/16 VDC or so.

73 de Tom, W3IWI

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