Connecting 4 wire optical switches for homing to ESS & MB3

[[email protected]]

I’ve been looking and cannot find the exact answer I need for connecting my OPB830 optical homing switches to the MB3.

I know I need a resistor to get the mA down to under 50mA but I am having a hard time with where I connect the 4 wires these switches have. These are for homing so there are three switches.

I was planning on 24v from the MB3 to the Red/Anode wire with a resistor in between. All three switches would use this once 24v output.

I think the black/cathode wires goes back to the 0V input. So all three can go to the same one correct?

Then I’m lost as to how to connect the white/collector wire and the green/emitter wire. My old controller had a two small, powered BOBs (one board had two homing switches and the other had one) that the white wires went to the same connection, reds to the power but the black wires and green wires had their own connections. Then the BOB had a two wires that went back to the main controller board.

If you can point to a forum post for this or can answer it directly, I would be forever grateful.

[Weerasak]

Here we are.



Be careful when using this electronic part. The operation can be disturbed by strong sunlight or ambient light.
It's recommended to use industrial sensors.

*Note, don't forget to make the input accepts 5V by soldering the solder-bridge.

[[email protected]]

Thank you very much!

This switch can take up to 30vdc but no more than 50mA so wouldn’t it make more sense to use 24v with the correct size resistor instead of 5v?

I’ve been using these switches for several years on this machine so they’ve been good without any issues with light etc but they were being powered with a 5v supply before.

[[email protected]]

I also wanted to ask which wires from all three switches are safe to combine to cut down on the number of wires needed running to the machine and number of physical connections on the board.

[Weerasak]

Because of the electrical characteristics of the components and the high safety margin idea. I came up with the low-voltage schematic in the first version.

However, in the situation where MB3 was already installed, it is difficult to flip the board and make the solders. then the high-voltage schematic is a better choice.

In the simplified schematic below, We need to increase the size and value of resisters to stand up to the heat that builds up. The output of a transistor can stand up to 30 volts. There is still some margin left for handling 24 volts from MB3 inputs.

[[email protected]]

Thank you very very much! I thought that would work but wanted to be sure.

And you would put the resistors nearer the switches instead of in the control cabinet for heat dissipation I'm assuming?

[Weerasak]

In the schematic, the resisters are placed on the switch side because I wanted to make it look simpler and try to make less wiring. But in the real world, attaching those resisters to the MB3 terminal or a separate terminal may be better.

The technique of choosing the right resistor values that always works for me is, using an amp meter in series between the resister and LED diode (inside the opto). The meter will tell you the exact current flowing through the LED diode, and then you choose the right resisters according to what the specs say.