120Volt Infared Sensor to Arduino

[windozeuser]

Hey Board,

I have a 120VAC In-fared sensor and I need to interface it to an I/O pin to the Arduino. I'm making a counter, and I want to count every time the sensor "Sees" something. So it would be a change in the Digital I/O pin, as an interrupt.

The problem I'm having is that the sensor is 120VAC and the Arduino I/O pins are 5VDC also it seems the sensor reads about 2.9VAC RMS when it sees the thing I want it to see, and the voltage increases to 116VAC Rms when it doesn't. It seems I need a circuit that can sense increasing AC voltage to trigger a digital 5V on/off response. Not sure how to approach this. I was measuring with a multi-meter, not sure if this sensor operates on current or voltage, it controls a solid state relay as the input to it in the device I'm modifying, then the relay controls an actuator. So the relay coil is connected directly to the sensor.

The sensor is an MP-D0130A but I cant find any datasheet on it..

 

[windozeuser]

Another Idea, in the device, when the photo sensor "sees" something it operates a large motor, it has a large coil, I was wondering if a possible hall effect circuit would be able to detect this? Like if it goes over a threshold value it means "We detected the motor working" so send a digital 1 to the Arduino?

Since the motor gives off an EMF would the hall effect sensor be able to pick it up? This would probably be easier/safer to interface since its isolated from the 120VAC mains this way

 

[windozeuser]

What type of Hall-effect sensor or circuit would I need to sense the magnetic field of the AC motor? I imagine it will be changing a lot in a short period of time, I really just need to sense if the magnetic field is strong once, so I know the motor was just energized. I know there are north pole and south pole hall effect sensors, but the AC motor will have a huge magnetic field around it, not sure what sensor I could use to detect its presence? Would it be changing between north and south poles at 60Hz?

 

[ChrisP58]

Could you put a relay with a 120VAC coil across the motor? Then just look at the relay contacts with the Arduino.

 

[windozeuser]

Could you put a relay with a 120VAC coil across the motor? Then just look at the relay contacts with the Arduino.

Freaking genius I like it, keeps it isolated from the high voltage, I could just debounce the normally open contact like a regular switch right?

 

[ChrisP58]

Freaking genius I like it, keeps it isolated from the high voltage, I could just debounce the normally open contact like a regular switch right?

Yes. Treat the contacts like a regular switch.