Using the Conductive Probe with Carbide Motion (2 things)

I guess what I meant by that is the End Mill or Bit is conductive and is part of the circuit, so one of the alligator clips goes on it or the collet. The part that lays on the working surface, assuming it’s wood for example, also needs to be conductive and flat. The other clip goes there. It doesn’t matter which clip goes where as it only completes a circuit. I took a piece of plan solid PCB and machined a part that looks something like a keyhole. The circular part is where the Bit (aka conductive probe) makes contact. On the part of the keyhole that sticks out, I bent a short piece of solid copper wire to a 90 deg angle and soldered it onto the PCB for a nice place to clip on.

I can send a picture if interested. Does that help?

With $6=0 most of the time it just flat errors out, occasionally it will move -.02mm to -.03mm given a -10 command before error out.

As for the connectors. I ordered the connector and connector terminal from digikey. I’ll admit it isn’t a perfect fit, the connector is a little wide. Still you can squeeze all X, Y, Z, and Probe connectors on.

Do you have a VOM? If so, you can turn power to the controller and measure voltage between the 2 wires. Should be a little over 3 volts at least to trigger the arduino pin.

A volt meter? Yes, I do. I will run home from work over lunch and get a measurement.

Edit: I get a reading of 2 volts across the probe

So since it isn’t above 3 volts, is that why grbl errors out?

The probe input relies on contact closure to ground. The PCB likely uses the internal pull-up of the mCU or some external resistor… who knows what logic-level the PCB operates at?

So yes, arduino’s read digital pins may require a certain level not to sure.
If you can find a 3V source and a 10k resistor, you could probably make it work. But that indicates there is something wrong with the controller board to me.

mm… I just wish Carbide3d would respond… I’ve called @ApolloCrowe a few times already, and sent the normal emails. It would be nice if someone could talk you through it on the phone.

The 2.4v has a 5V line on the left above the fan connector. Could that be used to trigger? I’m sure some type of resistor or filtering would be needed, but that is all foreign to me.


Notice that this new forum section was just created yesterday and the subjects were migrated from the normal course of dialog where the Carbide guys are gonna focus attention and/or reply. I’m unclear if they consider touch plate or conductive probe operations as supported operations, however due to the current location of this discussion I’m leaning to “unsupported” nature of an operation like this.

I just measured my PROBE inputs, and sure enough, 3.3V. Your low level input reading smacks of something wrong or misconfigured. Unsure how the UNO ports are protected (if it all), but I’d guess they’re pretty standard when it comes to low-level mCU. I’ve done a lot of embedded PIC and MSP430 development and both of these platforms provide TRIS/Port setup for ins/outs/pullups/pulldowns/etc… certainly Arduino family mCU provide similar operations.

I’ve run the Triquetra G-Codes via UGS with my v2.3 CC controller and had success that way… someday once I’m ready to dive in I’ll roll up sleeves and get familiar w/G-code…

The probe input goes to a buffer with an external pull up resistor. The probe is activated by pulling the input pin to ground when the probe is closed. The Vcc voltage has varied between 3.3 and 5, depending on the board revision you have, but it’s irrelevant here- you just need the input line and ground.

Regarding the Unsupported category, the vast majority of users who come here don’t post, they just read. For those people (and many are new to CNC) we don’t want there to be confusion between the workflow that we support, and things that are possible, but unsupported. You would be shocked at the number of support tickets and phone calls that are triggered by this kind of thread.

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All the Carbide Motion boards have an external pull-up on the input lines, so nothing needs to be added (nor should it). Like Rob says what matters is the probe input pin and ground. A quick test would be to short those two pins with a pair of tweezers or a jumper during a probe cycle so we can verify that the hardware is working.

I totally understand having a dedicated discussion place that’s outside your supported workflow/toolchains, gentlemen… the fact that you both chimed in here is admirable given the wave of stuff you do daily…

Thanks Jim. In case you didn’t see this:

We are going to have an “official” probing system in the near future, so hopefully that’ll eliminate the hacking required to do it now.

Is it a good voltmeter or a harbor freight/Chinese poor quality brand?

I know nobody has mentioned it and I’m not trying to hurt feelings but the level of workmanship on your wiring is very very poor and could be all your problems. Get the proper connectors and the proper fittings and then let’s talk.


Hadn’t seen this… it looks fantastic. Having direct line mCU inputs is always potentially hazardous for ESD with MOS devices, even with a TVS on the line. Your active approach is novel and commendable.

This with in-line tool changing will really enhance workflows.

Jogging is still a bit glitchy on my machine with v.364

So I finally figured it out. Thank you all for the help. Especially the 3v part. The original machines were shipped out with a fan. @Jorge The total current draw with the fan was too much to keep the voltage up to trigger the probe pin. After unplugging the fan the voltage on the probe pin went back to normal, and probing started working.

@jimidi What are direct line mCU inputs? Baby steps, can’t you see this thing is hacked together :slight_smile:

Without a controller schematic, my guess is the probe, limits and all the other inputs on same the molex header are direct inputs to the Arduino micro-controller.

@atrueresistance, I missed it in the images you posted, but when Apollo said you had the fan connected I belatedly realized what was happening. We got rid of the fan a while back, and because real estate is a at a premium on the board, the only place we could fit a connector for the touch plate was where the old fan connector used to be. It isn’t a voltage issue, it’s that the fan is interfering with the probe pin. Don’t plug the fan in and you should be good to go. The new boards have really good heat management so the fan isn’t needed anymore, in case you’re worried about performance.

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What limit switches are you using in this pic