Over the holiday break I started to think about a way to activate and deactivate the monitoring system I'm making when the dust collector is turned on or off. I may end up running the whole thing on battery power and having the Arduino sleep would help extend the life.

I thought initially about tapping into the power line going to the blower motor and sensing the current but that is a bit of a pain in the ass.

I thought about looking at the pressure across the blower, it should tell me without a doubt if the system is on and reduce the risk of running with a dirty filter. If I have high pressure differential but low flow, there would not be much pressure generated at the filter pressure sensor. It would take some calibration but the chart below indicates that I should have some measurable level of pressure at even the highest flow rates.

I am thinking of another freescale/nxp pressure sensor for this measurement. I am going to put it on the cyclone drum as that is exposed to the same vaccuum as the inlet. I am cutting into that for the dust bin height measurement anyway.