Photoelectric Sensor Wiring, Setup, and Troubleshooting

In this article, we will be talking about the photoelectric sensor wiring and setup. We will be talking about the 24-volt DC Through-Beam, Retroreflective, and Diffused photoelectric sensors. These are the three basic types of photoelectric sensors and they come in many different shapes and sizes.

Photoelectric sensor mounting

Some of the larger photoelectric sensors have holes in the sensor body that can be used to mount the sensor and some of the smaller photoelectric sensors require some type of bracket to hold them in place.

You can buy premade brackets to mount these sensors and these brackets can be adjustable or non-adjustable.

Photoelectric sensor application

A belt conveyor transporting an empty box will be used to explain how to set up each sensor. On the conveyor below, the sensor will trigger the Motor Starter to start or stop the motor. We will also talk about troubleshooting these photoelectric sensors.

Photoelectric sensor wiring

First, we will show you how to wire the Through-Beam photoelectric sensor emitter. Through-Beam sensors have two separate devices, one is called the emitter and the other is called the receiver.

The emitter is what sends the light out and the receiver is what catches the light.

Both of these sensor devices will need to be connected to 24-volt DC power. The receiver will also be connected to the 24-volt DC Motor Starter coil.

To be safe, make sure the power is turned off before connecting any wires.

To connect the emitter of the Through-Beam sensor to 24-volt DC power, connect the brown wire to 24-volt DC positive and the blue wire to 24-volt DC negative, just as you see in the picture below. The emitter is now hooked up and ready to use.

The wires of the Through-Beam receiver, the Retroreflective sensor, and the Diffused sensor all get connected to the belt conveyor in the same way.

So to connect 24-volt DC power to any of these three sensors, connect the brown wire to 24-volt DC positive and the blue wire to 24-volt DC negative.

Now connect the sensor output black wire to the 24-volt DC Motor Starter coil to complete the wire connections. With the sensor wire connections being complete, you can now turn the power back on.

1) Through-Beam photoelectric sensor wiring

Now we will show you how to mount these three sensors to the conveyor starting with the Through-Beam sensor. As you can see in the picture below, we are useing a premade adjustable bracket for all three sensors, to make mounting and aiming of the sensors easier.

With the Through-Beam sensor, use a straight edge to line up and mount the emitter and receiver, so they are straight across the conveyor belt from each other.

Adjust the sensor if needed and tighten everything down to lock the sensor in place.

To check alignment, block and unblock the sensor with your hand to make sure the sensor indicator light turns on and off. The Through-Beam photoelectric sensor is now ready to test.

With the Retroreflective sensor, it needs a reflector to work. Use a straight edge to line up and mount the sensor and the reflector, so they are straight across the conveyor belt from each other.

Adjust the sensor if needed and tighten everything down to lock the sensor and reflector in place.

To check alignment, block and unblock the sensor with your hand to make sure the sensor indicator light turns on and off. The Retroreflective photoelectric sensor is now ready to test.

2) Retroreflective photoelectric sensor wiring

With the Retroreflective sensor, it needs a reflector to work. Use a straight edge to line up and mount the sensor and the reflector, so they are straight across the conveyor belt from each other.

Adjust the sensor if needed and tighten everything down to lock the sensor and reflector in place.

To check alignment, block and unblock the sensor with your hand to make sure the sensor indicator light turns on and off. The Retroreflective photoelectric sensor is now ready to test.

3) Diffused photoelectric sensor wiring

To mount the Diffused photoelectric sensor put the empty box on the conveyor where you want it to stop, as per picture below. Mount the sensor at the front edge of the box, adjust and tighten everything down.

Diffused sensors have a sensitivity adjustment screw. If the sensitivity is set too high the sensor might stay on all the time. If the sensitivity is set to low it might not turn on.

To set the sensitivity for this belt conveyor, put the box in front of the sensor in the middle of the conveyor belt. Adjust the sensitivity until the sensor indicator light just turns on with the box in this position.

Block and unblock the sensor with the box in different positions to see if the sensor turns on and off and this will also double-check the sensitivity setting. The Diffused sensor is now ready to use.

Photoelectric sensor troubleshooting

To test out these sensors we will place an empty box on the conveyor belt and start the conveyor. If the photoelectric sensor is set up correctly the box will travel to the sensor, and then shut down the conveyor motor when it blocks the sensor.

If the photoelectric sensor is not working correctly, the conveyor motor might not start, it might only run when the sensor is blocked, or it might not turn off.

A) The conveyor does not start

If the conveyor does not start, the sensor might need to be adjusted or it might be dirty.

1) Clean the lens of the sensor and check the alignment by blocking the sensor and watching the sensor indicator light to see if it turns off and on. If the light turns off and on, the sensor is aligned.

2) If the light doesn’t turn off and on, adjust the sensor so the emitter and receiver are aligned.

3) If the conveyor still does not start, look at the Motor Starter and block the sensor again. If the sensor is working correctly you should be able to hear the Motor Starter contacts close when the sensor gets blocked.

4) If the Motor Starter contacts do not close, the sensor or sensor cable is bad and will need to be replaced.

B) The motor only runs when the sensor is blocked

If the motor only runs when the sensor is blocked, it is probably in dark-on mode. Flip the mode switch to light-on mode to correct this issue.

Some Photoelectric Sensors have a light-on, dark-on mode selector switch. Light-on mode means the sensor output turns on when the receiver sees the emitter light.

Dark-on mode means the sensor output turns on when the receiver does not see the emitter light.

C) The conveyor motor stays running

If the conveyor motor stays running,

1) the sensor might be misaligned and in dark-on mode,

2) the sensor or the sensor cable might be bad and will need to be replaced.

Summary

In review, by reading this article you have learned about the three basic types of photoelectric sensors Through-Beam, Retroreflective, and Diffused; How to connect the wires of these sensors and how to set them up on a belt conveyor. You also learned how to troubleshoot these photoelectric sensors.

Please let us know if you have any questions about wiring or setting up 24-volt DC photoelectric sensors in the comments below and we will get back to you in less than 24 hours.

Got a friend, client, or colleague who could use some of this information? Please share this article.

‍