J325 Z axis proximity sensor ???

[lavrgs]

The X and Y axis limit switches were pretty simple but the z axis is different. It's got 3 tiny wires and I'm guessing that there needs to be a voltage applied; 12v, signal , ground ...right? I have brown , blue and black and don't know how these work so how do they get hooked up? I have checked with a DVM and there is no continuity between any of the wires.

[Al_The_Man]

Is this a new unit? It should have make/markings on it.
The three wire kind require power, common, and output, they can be PNP or NPN, this decides how the output is connected.
The common connections are Brown +, Blue Com, Black load.
But there are variations out there, this is why you need to refer to the manufacturers info and the machine schematic to find out if the device switches to + or common (Sink or Source).
Al.

[lavrgs]

The unit is an existing item. Do you think the contacts are written on it?...if they still exist... What about realignment? just close?

The information I have for the Tree does not include any wiring for the proximity switch. The PNP or NPN part had escaped my electrically challenged brain except for the fact the breakout board I have could use either type.

[Al_The_Man]

The first thing to check is if the label is still readable, make model etc.
Al.

[elnerdo]

the wiring is as follows for the standard Tree z-axis proximity sensor:

Brown wire = +24V
Blue wire = Ground
Black = Signal (+24V) when the signal is sensing an object

the gap should be set to +.035"

on the standard control, the output of the signal wire feeds a relay which is part of the (limit reached) e-stop circuit.

if you are using the sensor for home with your Mach3 setup, i would back the sensor away from its current position by whatever you think the tracking error will be for your servo system since the sensor is basically the mechanical end of travel for the ball nut.

[lavrgs]

Thanks for the hook up info!! This is going to be interesting because I don't have 24V...was there a transformer that provided 24V? If there was that may be the path or perhaps I can run 12V - these things take a range of voltage from what I've seen

[elnerdo]

the +24V was provided by the power supply connected to the controller. if the controller passed its power-on self test, it would supply +24V to the safety circuit which included the limit switches.

if the limit switches were not tripped, then the reset button would see +24V. hitting the reset button would then close the main contacts to the machine and enable the drives.

a good way of doing this kind on thing on a home brew system is to buy a "safety relay" from ebay. they are usually configured with a set of "and" relays that could accept your limit switches directly. assuming everything is in a safe condition condition, the safety relay would output 24v for the drive enable signal.

[lavrgs]

This may be a dumb question but does the safety relay provide the power?

[lavrgs]

Thanks for all the info on hooking up the sensor. I got it to work yesterday and found that it must be a pnp vs. npn as I had to put a 1K pull up resistor across the signal and ground leads to get it to work.

[elnerdo]

cool, glad to hear you got it working.

i've seen safety relays that do have a little transformer to provide dc power. there's one made by telemacanique (the xps-at) that does this, but most (i think) rely on a 24V supply.

[lavrgs]

When I looked at proximity sensors, in anticipation of the one I had not working, it seemed that the ones I looked at had a wide range of control voltages that could be applied. My breakout board supplies 12VDC and it seems to work so I'll leave well enough alone for now.