These switches cannot be used for combined homing/limits - the flickering output immediately triggers a limit fault after homing as it sees the flicker as the next sense input. Probably just crap sensors.
My fix was to use them for homing only, then add soft limits to control the position limits on all axes - the mill will always be homed when in use so this seems a safe option.
However, as the sensors all use one input, it sees the flickering as the next axis sense and just zeros all the dro's - did i say these sensors are crap?
The fix - modify the home-all button script to something like this for all axes...
DoButton( 24 )
Code "G53 G1 z-3 F500"
This runs the home, zero's the DRO, then steps back 3mm which is enough to get the target clear of the sensors, then it moves onto the next axis and so on. It works perfectly but does leave the tool at X3, Y3, Z-3 but then you can jog back if it matters as the soft limits will stop a crash. It does NOT work without the While IsMoving lines in there. Debounce does NOT make any difference and is now set to zero.
I guess I could add a move to zero on all axes after the homing finishes, just to park it all at zero.
A video of homing working nicely...
Now i can start final wiring and finish the build, damn good fun playing with it though
13-03-2016 #52These switches cannot be used for combined homing/limits..Clive
Dave these switches 100% do work for both I use them all the time. It's either your using them wrong or possible the BOB doesn't work like you think.?
How you have worked around the problem may well work but I wouldn't trust for repeatabilty.
I think the answer to the problem is you'll need to use 10k resistor to force the input high.
Last edited by JAZZCNC; 13-03-2016 at 12:12 PM.
ok, but the inputs are already pulled high internally by 4k7 so surely another pull-up would be bad??
You can see the LED on the sensor flickering unless the tip is 100% covered by the target, this does not match my previous experience of inductive sensors where they are either on or off - NO flickering!
This is not a PNP/NPN issue, these are NPN and wired for NPN normally open.
JAZZ, you use sensors, does the LED flicker?
here's a video...
Even the super cheap Ebay ones work ok dave.
You haven't wired the switch powers in series have you.? That flickering looks like struggling for volts.!
No, all wired in parallel as described in manual, I have a quality bench psu and will test them on that now...
If you fully cover the end with the target the LED is solid on, but mach picks up the very first flicker and takes that as the position, as expected.
Maybe these are fakes or junk clones which have the output conditioning circuit missing??
Nah I'd be suspecting the conflict between swithc and BOB my self. The input isn't conditioned correctly. Stick a 10K resistor on between 12v and pin 10.
Worst case is it will slow down the input reaction time.
I've had this before with prox switches and PMDX board using ESS.
Thanks Jazz, I have some updates..
This seems to be a PSU issue believe it or not!
The BOB is powered from a little 15v SMPS, the sensors are powered from the BOB which has a DC-DC converter and puts out 12v.
First test was to put a sensor on my variable bench PSU, they worked perfectly! Clean on and off LED - perfect.
So i tried running the sensors direct from the 15v PSU - these are NPN so supply voltage does not affect the output signal and the 0v in/out is common on the BOB - result was that it worked ok UNTIL I took Mach out of reset when the flickering returned - baffled!
Next i tried running the BOB from the bench PSU - perfect result and i could even enable the limits (on one axis anyway) and it all worked as I first expected it should.
So - do we have a duff PSU, are these sensors sensitive to SMPS output?
I am not sure what to try now - baffled.
Maybe add some uF to the output of the supply and maybe some filtering?
I might get the 'scope out and see whats on the supply.
Get a different PSU? (this one came from CNC4YOU as did the BOB)
Here's another oddity - the plasma always wipes out the radio as soon as the drives are enabled, now it seems this build does the same - as soon as the drives kick in, the radio gets washed out.
Both builds use SMPS and all parts came from CNC4YOU. Food for thought.
Last edited by Davek0974; 13-03-2016 at 02:29 PM.
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