Centroid Community CNC Support Forum

I was given a nice looking probe that has the advantage of being quite short. The only problem is that it is rated for 12 v. If I supply 12 v to the probe will the probe detect and signal ports on the acorn board respond to the 12v input

Acorn inputs are sinking and expect a COM or 0V to pull them low to activate. Please do not wire 12v into the input. I assume you have a separate 12V power supply for that probe? If so tie the ground and common together with the Acorn power supply. Without more info or pics on the probe or power supply we'd be just guessing on how to wire it up.

To add to Shawn's info, if your 12v probe is npn you can try and test to see if it will sink enough current to trigger an Acorn input, if it is pnp, it will not work

A pnp probe or proxy can be made to work. I did one on the last axyz machine to be able to reuse their tool setting probe built into the atc rack. I use a solid state relay.

Basically wire your probe to activate the solid state dc to dc relay input. They work on 3-30 volt input. Then run the acorn input line through the output of the solid state relay to gd. The plus of the solid state relay output goes to the acorn input. The Both minus's for the input and output of the relay go to ground. Then the + of the input of the relay is triggered by the probe.

When I have an output signal from an atc spindle that gives power when activated instead of ground, I use these to get around the issue also.

It may be you need another 12v power supply, but they are cheap, and just tie all the grounds together. If you post specs and info on the probe, there may be other options.

Yes, I have 24V/12V meanwell power supply with COM tied to both. Both the KP3 and this gift probe appear to be npn. My basic question was to ask if anyone had an experience 12V vs 24 input (same COM)_ to the IN7 position on the board? My references on TTL logic on a generic board says only 2V to generate a TTL high. This not a generic board and thus the question.

Plan"B" would to use an optocoupler to mimic the 24v signal onto a 12 v signal. Any thought on this?
Thanks a bunch for the feedback

Optocoupler or SSR will both work if done right...

Uwe

As stated a relay or SSR could work if needed to trigger the input and pulling it low. The Acorn inputs are pulled high internally with a pullup resistor so applying 12v to a circuit that's already pulled high to 24v might be an issue. I've never tried it and wouldn't want to.

That would not harm anything, but the difference between 24V and 12V might or might not activate the input optocoupler. Connecting an Acorn input to +12V would cause it to carry half as much current as closing it to 0V as designed.

However, a probe with an NPN interface, that happens to use 12V to power its internal circuits, probably does not close its output to 12V when not active; it probably just closes its output to 0V when active.

So, if it has an NPN interface, and the commons of the probe's 12V supply and the Acorn inputs' 24V supply are tied together, then it is likely to work just fine without any special interface circuitry.

That makes sense and I agree that if it does not close it's output to 12v when not active it may work with the signal wired to the input on Acorn as is and pull it low when active. He's not sure if it's even NPN as he states "it appears to be NPN".

That said, I don't like adding additional relays or SSR's to inputs anyway that are critical like probes or tool touch off devices. Those few milliseconds of delay can throw off the measurement by a very minute amount. When cutting a wood design maybe that's not critical but when cutting aluminum with precision it may show up in the cut.

Since the OP doesn't tell up anything about the probe other than it's 12v we are just guessing what it does. Maybe he'll elaborate on the make/model or a link to the manual as that would be more helpful.

Centroid does offer the Ether1616, which feature SIP sockets, which allow groups of 4 inputs, to be configured to 24, 12 or 5 volts.

Ether1616:https://shopcentroidcnc.com/shop/cnc-ex ... nsion-kit/

Sip Configuration: https://www.centroidcnc.com/centroid_di ... pdf#page=5