Detect machine tool running

[scott216]

I'd like to use a current transformer (CT) to detect if a machine tool in my shop is running so I can automatically turn on dust collection. I don't need to measure how much current there is, I'm only interested in if it's on or off. I know you can connect a CT to analog input on an Arduino (with some circuitry in between to get the voltage right) and sample that, but I'd prefer to connect to a digital input. I have some current transformers that put out about 16mVAC per amp. Machine tools will draw from 5 to 20 amps. Any recommendations on a circuit to put between the CT and Arduino digital input?