embedded_sys
Member
I have a main line stretching about 1200 feet. I would like know if the line has been cut when the main line doesn't have voltage. I'm currently thinking of putting a 100K resistor between the hot wire and the ground wire at the end of the line and applying a 3.3VDC or 12VDC voltage with a resistor to the hot line at the beginning of the circuit. This would create a simple voltage divider that I could measure. If it is a 3.3VDC, I'd know the line was cut. If it is lower, the set voltage of my voltage divider, I'd know the line is cut.
The biggest problem is knowing how to put 3.3VDC on a line that sometimes has 120VAC. I would never try when 120VAC is on the wire, but my worry is someone will accidentally apply 120VAC to this line when I am applying 3.3VDC. Obviously this would destroy my DC circuit. I've thought about using an isolated dc-dc convertor to apply the voltage just for that line to reduce the risk of the rest of my circuit being damaged. Is there a good protection method I can use to make this safe?
The biggest problem is knowing how to put 3.3VDC on a line that sometimes has 120VAC. I would never try when 120VAC is on the wire, but my worry is someone will accidentally apply 120VAC to this line when I am applying 3.3VDC. Obviously this would destroy my DC circuit. I've thought about using an isolated dc-dc convertor to apply the voltage just for that line to reduce the risk of the rest of my circuit being damaged. Is there a good protection method I can use to make this safe?