Expert: Dave Nyce - 12/31/2011

Question
Hello
I'm planning to design a system to detect the absence and presence of 110 dc voltage but I'm not sure what appropriate sensor suits here.I want its out put be fed to the microcontroller for processing.
please help
thank in advance.

Answer
You could use a simple voltage divider with the 110VDC going through a 100k resistor, then through a 4.75k resistor to common.  The point between the two resistors (we'll call this the voltage tap) will have 5VDC when the 110k is connected to 110VDC. The voltage tap will have 0VDC when the 110k is connected to 0VDC.  Bring the voltage tap into a uC pin that has an A/D converter, and it will measure the voltage.

Hope this helps!

Dave