Hi,

I'm looking for ideas on how to Monitor current for a 24V dc fan?
I just need to know if the fan is consuming any amperage, and if the fan is on I need a 17 to 24V dc signal going to my PLC input.

Also all the components will have to be on a PCB.

Couple of ideas I tried was high side current monitor with using op amp but this will not work because if the wire get cut the shunt sensor still using amps, and the Low side I never got it work.


Please Help

 

Tons of simple hall effect sensors/schematics out there..
Can you just feed the 24V signal that feeds the fan to the PLC also. Or do you need to ensure the fan hasn't gone dead on you.

 

I need to know if the fan is working

 

This brings the idea of "air flow". A mechanical answer is a "sail switch". An electronic answer is a thermistor. Are you familiar with these? Would one of them suit your purpose?

 

Thermistor would not work for me because we would have to buy a RTD Point IO Card. We would like to use our normal 1734-IB4 point IO card.

Also when the fan is running at full speed it avg. about 2A. I found some IC that would do maybe up to 500mA max.