GRBL Probe wiring sense check

Using Arduino Motors, Mechanics, Power and CNC
1

Not exactly Arduino but I am running GRBL on a board with a ATMEGA328 and I figured there would be some expertise here that could confirm if my idea would work.

Basically I want to wire up a basic continuity probe to probe pins that also turns on an LED when the probe is triggered.

From what I've read the GRBL probe pin is set as an input using the internal pullup. So my plan would be to wire up an led with resistor, powered from the onboard regulator on the board, so that when the probe is triggered it connects both the cathode of the LED and the pin to ground.

I drew it up on a circuit simulator and it seems to be doing what I want but I thought I would just check this isn't going to cause any issues.

Below is a screenshot of the simulator, the push button is representing the physical probe plate.

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Thanks.

2

The LED will act directly when the button is activated so no fuss with GRBL.
In the GRBL world end switches exist. How to establish certain logic due to an activated switch is beyound my experience.
"Basic continuity" is new to me. End switches, dedicated to certain axles, X, Y or Z I've heard of but "Basic".... Is it a kind of emergency stop function You aim at?

3

Perhaps the word basic isn't correct, perhaps standard is better.

Just to be clear here are some more details.

All the logic already exists in GRBL.

There is a probe pin that, like the end stop pins, is triggered by shorting it to ground.

Connected to this pin is a piece of metal of a set thickness. This piece of metal is placed on top of what you want to mill and the cutting head is moved over the top. A ground is connected to the bit and a probe command is given, the bit will move down a preset distance or until the bit touches the plate, shorting the pin to ground, triggering the input.

I want an LED indicator so that before the probe command is given the user can quickly touch the plate to the bit to ensure the probe is working,

There is an indicator within the gcode sender program but unfortunately it's a few pages deep and I'm trying to make this as simple and fool proof as possible as the average user will be fairly inexperienced.

4

It sounds like a height, Z axle, calibration procedure switch.

5

That would be another way of refering to it.

The pin is labeled as probe so that's what I call it.

Again, perhaps Z height probe would have been a more descriptive name.

The main thing I just wanted to double check was that wiring the led to the same pin wouldn't damage anything in the chip.

What I read online said it should be fine but it never hurts to double check.

6

Are you sure it is not an "edge detector"?

7

I will not, provided the resistor limits the current to a safe LED current level.

8

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