Motion detector to monitor & open circuit when motion stops

[BillB]

I’m wondering if it is possible to take an off the shelf motion detector and rewire it so it opens the circuit or turn on lights when any motion STOPS. Basically doing the opposite of what it is designed to do. OR is there any other way to do this with a standard off the shelf motion detector and other components. I’m not an electronics’ guy so I’m looking for a real simple way to do this.

Here is the need.
I have a CNC milling machine and many times the machine will stop running as a result of many factors. When it dose it is sitting there doing nothing and costing me money. Many times over night. I want to monitor the machine when it is running and IF it stops running I want it to trip a circuit that will sound an alarm letting me know the machine has stopped.

IS this possible? How

 

[LTX71CM]

Invert the output of the motion sensor you get and it would provide the signal you're after. I would add a several minute retriggerable timer so if the machine makes a temporary stop, long slow path, etc. you wont get a false alarm.

 

[Mikebits]

Your machine may already have a machine stopped alarm output. It may be a hidden terminal board or such. Check your manual. If not you might be able to tap into a signal that indicates machine status, contact the CNC manufacturer.

 

[BrownOut]

Monitor the spindle motor current.

 

[Boncuk]

PIR motion detectors are normally equipped with an NC/NO relay output. Just connect your load to the NC terminal.

Boncuk

 

[BrownOut]

What good is a PIR detector anyway? It works on body heat. Sure if a machine stops, it will cool, but will the rate be enough to trigger the detector? Wrong tool for the job, IMO.

 

[gerty]

I recently did something similliar for a friend with a wire EDM machine, when the EDM wire broke, the machine stopped.
What I did was wire an indicator light to the output of the cooling pump contactor. The cooling pump shuts off when the machine stops. I wired a 220 volt relay to the output of the contactor for the pump. Pump running, contacts close turning on green light, pump stopped relay de-energized and red light comes on through normally closed contacts on the relay. Light is powered from a 120v outlet next to machine. The light fixture itself is an old traffic light mounted on outside wall of shop that the owner can see from his house.