New Build, Aluminium Frame Router/Mill

**JAZZCNC** · 12-03-2016

Originally Posted by Davek0974

These ones, they seemed to be the most common type, NO, NPN.

LJ12A3-4-Z/BX

How are you connecting the switches to the BOB.? What pin does the Black wire go to.?

**Davek0974** · 12-03-2016

On my CP0-10V bob from CNC4YOU it goes to pin 10 and i am using input 10 in P&P settings, you can see the LED on the back of the sensor flicker as the target is starting to cover the end of the sensor, when fully covered the LED is on stable.

The sensors are powered from the 12v output on the BOB as shown in their diagrams.

**JAZZCNC** · 12-03-2016

The manual shows PNP swithces and your using NPN. Take 12V to pin 10 and Put Black wire to Gnd. Then it will work.

**Davek0974** · 12-03-2016

Originally Posted by JAZZCNC

The manual shows PNP swithces and your using NPN. Take 12V to pin 10 and Put Black wire to Gnd. Then it will work.

This is the manual i used http://cnc4you.co.uk/resources/CP0-10V.pdf, the switches and sensors pull the pins down to activate, I guess thats active low, and i thought NPN was sink or active low output i.e the pin is pulled high internally and the sensor pulls it low?

**Davek0974** · 13-03-2016

Sorted

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 )
While IsMoving()
Wend
DoOEMButton(133)
While IsMoving()
Wend
Code "G53 G1 z-3 F500"
While IsMoving()
Wend

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...
https://youtu.be/T2CeluqhRl4

Now i can start final wiring and finish the build, damn good fun playing with it though

**Clive S** · 13-03-2016

These switches cannot be used for combined homing/limits

I don't think it is right to condemn the switches and say they don't work for combined use. Lots of people use them it all depends how they are wired. NPN and PNP are different and have to be wired different.

**JAZZCNC** · 13-03-2016

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.

**Davek0974** · 13-03-2016

Originally Posted by Clive S

I don't think it is right to condemn the switches and say they don't work for combined use. Lots of people use them it all depends how they are wired. NPN and PNP are different and have to be wired different.

I didn't mean "these" as in all sensors, just maybe these super cheap eBay ones possibly, they were only £2.50ea. Previous experience was that the LED & output was either ON or OFF, not flickering depending on how close the target is.