New Machine Build- probotix to inductive prox sensor

[xkadet]

I can run wires and solder, but I'm not an electronics whiz.... I'd like to use a bunch of new inductive proximity sensors that i picked as the limit switches on my prototype probotix driven (4 axis 400in/lbs version) cnc router. Can any one steer me toward a circuit that will convert the inductive sensor signal to the something the probotix board will see as a typical mechanical switch-- doing the same thing? I assume, since the limit switches are all ganged together in series, and the switches are normally closed, they must be dropping a voltage to 0 at some pin on an IC somewhere --until the circuit is breeched, or some other simple signalling approach... The inductive sensors have 3 wires typically as opposed to the mech switches with 2. How do you use inductive sensors on the hobby side? (serious hobby side...)

[keebler303]

I assume your probotix board operates with 5V signals?

Most proximity sensors like you describe are powered by 12-24V. One wire is ground, one is power, and one is output. The way you hook them up will depend on the type of sensor they are. Do you have a part number? Do you know if they are NPN or PNP type? That changes what you will have to do. Also, do you have a link to a manual or something about this probotix board?

I'll try to help but I need some more information first.
Matt

[xkadet]

One is a Baumer NPN IFRM 18n17202/L, the other is a Highly S12-02N-1.
Both appear to activate under 5V supply or more. The Probotix link to the controller board is here: http://www.probotix.com/manuals/PBX-2_manual.htm; link to the baumer version: http://www.sensorplex.com/pdf/IFRM_18_mittel_web_EN.pdf

I can't find any info on the other one on the web, so I'm no help there. they both seem to work similarly, however.

From the schematic at "probotix" it looks like maybe the mech limit switches drop the voltage by grounding a pin for each axis. Hitting a limit opens the circuit so the pin goes to 5v (on board level) , high. This is as much as I understand so far. Thanks, for any and all help.
keith

[keebler303]

Your link didn't go to a specific product. I think you have this?
http://www.probotix.com/index.php?vi...&product_id=15

The schematic is here:
http://www.probotix.com/schematics/pbx-2_schematic.jpg

You have the right idea about how the inputs operate.

The Baumer sensor you have should work fine. It has an output which is normally floating and drops to 0V when it detects something. Your board has pullup resistors so your input pins will normally be at 5V. When the sensor detects an object it will pull the pin to 0V. So you need to connect the power pin to 10-50V, the GND pin to 0V, and the output pin should go to the input on your board. If you don't have another power supply available, I would use the 12V from your computer supply to power the proximity sensors.

I can't say much about the Highly sensor as I don't know which type it is. If it is NPN type as well, it will work the same as the Baumer. If it is PNP though, you need some other components on the output so you don't feed higher voltages into the logic on your breakout board. You could either use a voltage divider or a series resistor and a zener diode. I'm not sure which would be better.

The easy way to check is to power the sensor and measure the voltage on the output pin. If it is PNP type, the voltage will rise to near the supply voltage when it senses an object. If the voltage on the output stays near 0V no matter if it senses and object or not, it is probably an NPN and you can connect it the same way as the Baumer sensor.

[xkadet]

Thanks, the last post was what i needed to know. Now I need to hook up all the wiring and see how things work. I'll get back to this forum when i have more questions...

Thanks everyone for all the help.