[Lindzr]

Please excuse my limited electronics knowledge in advance

I am trying to wire 6 SN04-N NPN NO 10-30v proximity sensors to this KL-1212 breakout board ( https://www.automationtechnologiesin...face-breakout/ ) to serve as home/limits on a cnc router I am building. There are a few threads about wiring 12v sensors and 5v boards but I am still not quite 100% confident and do not want to fry anything.

After doing a lot of reading on this AFTER I purchased them I have come to realize that I probably should have got NC sensors for fail safe operation and that proximity sensors do not necessarily simply hook up straight to the inputs depending on various voltages etc, but at this point they are installed and all the cables routed in my machine so I figure I will see If I can get them working. I have up until now used mechanical limit switches on other builds which are pretty simple.

The KL-1212 board I am using does not appear to have a full manual, just basic pinout and wiring diagrams so I am not 100% certain about the specs of the inputs but they measure 5v when the board is on.

The second problem is that I am not 100% certain if the sensors have internal pull-up resistors or not from the specs, but they do measure 10k between the +v and signal (brown and black) wires so I assume that means they have an internal 10k pullup resistor..? Is this correct?

Anyway, I have wired up more or less like the diagram attached that was supplied with the board except that I was going to split the 6 limits into 3 pairs, with the pairs each wired in parallel, then each of the 3 pairs then wired to separate inputs on the board for x, y, z and operate them as shared home and +/- limits for 3 axis in Mach 3. The drawing shows 3 limits all wired to one input.

I have not connected the sensor outputs to the board at this point as I am not sure if I need to use resistors or perhaps relays to avoid frying anything. If I understand what I am reading correctly I should not simply hook the output wires from the sensor to the input on the board due to the 12v sensor and the 5v board and the fact that the sensors appear to have 10k pullup resistors internally? correct?

The board is powered with a 24v switching supply and there are 5v and 12v taps. The inputs measure 5v when the board is on. I am using the 12 v tap for the proximity sensors

Would one of you kind souls help walk me through wiring them up so I do not blow up my board?

If I do need resistors can you help with values and how I would wire everything up with the 3 pairs of sensors to 3 inputs layout I want to try (assuming that seems to be a logical way to hook them up that is, other suggestions would be considered)

thanks in advance!

[rodw]

I'd be surprised if your prox sensors have built in pullup resistors. I'm using 2.2k pullups on prox sensors in my 24 volt system on the manufacturer's recommendation..
You will need something to convert voltages. There are some signal chip solutions that do the trick. I looked on another forum for the part as it was mentioned recently but couldn't find it. Maybe you could use something like this which I found on a quick Google

https://www.automationtechnologiesin...face-breakout/

[Torchhead]

The board description shows to have opto inputs. That means you need to pull it low (to GND ) to trigger it. It has internal current limiting (pullup) to keep from burning ou tthe Opto . You first need to make sure the external (36V) voltage GND is the same as the input GNDS. If so you should be able to turn on an input (as can be seen in the MACH Diagnostics tab and INPUT STATUS) by shorting between an input terminal and the GND. If that works then all you have to do is make the OUTPUT of the Sensor pull to its GND pin (go low) which is tied to the same common GND . The output of the sensor is probably Open Collector. Normally you need a pullup if you want it to change the output pin BUT the Input of the BoB should do that for you. It will limit the current though the opto and provide the pullup. It won't hurt to have a pullup to the +12 bus if you want to measure the action of the sensor with it not connected to the Input .

The NO version is your best bet . NC are PNP devices and harder to make work.