[simpits-tech] controling a 28v circuit with a 5v

[David C. Allen]

While I like Genes transistor solution, you must commingle 5 volts 
from the controlling LED Circuit board and the 28 volts from the lamp 
power supply. A Opto isolator based transistor would provide the 
electrical isolation between the two power sources, but there still 
is a common ground. The relay was the cleanest solution because both 
the supply side and the ground sides are isolated.

Some of the LED Circuit Boards outputs are multiplexed so the led are 
actually turning on and off at a fast enough rate that the eye/brain 
thinks the led is ON. A relay on the other hand may just buzz, due to 
the multiplex frequency. Adding a capacitor to the relay input coil 
can eliminate the "Buzz" and provide a steady controled output.

Just another data point.

David
www.737FlightSim.com