CNC NVR switch triggering limit switch alarm

[MaximumBoof]

After building an enclosure for my DIY CNC (Arduino Uno + CNC shield) I bought an NVR (no voltage release) switch to be able turn my Makita router on and off safely from outside the enclosure.

However, everytime the NVR switch is pressed it leads to a limit switch being triggered and UGS entering an alarm state. There is no wiring between the router and Arduino.

Some observations:

- The limit switches will trigger even if the router isn’t plugged into the NVR. The router just needs to be nearby.
- I can take the router out of the enclosure and move it some distance away from all CNC electronics and using the NVR switch will still trigger the limit switches.
- I’ve tried the NVR on different plug sockets and no change.

Has anyone had similar issues or can think of a way to solve this issue? Any help would be appreciated.
Cheers!

NVR - https://www.yandles.co.uk/nvr-safety...le-w026/p20832

 

[Chrispy]

Sounds like electrical interference or a poor earthing.

 

[MaximumBoof]

Ah, I could only think of electrical interference. Do you have any tips to improve grounding?

 

[Sideways]

Stars are good, (earth) loops generally bad.
Tieing cables together in parallel bundles is generally a bad idea as it increases crosstalk.
Keep different types of cable apart also - like power cables which carry a higher current and signal cables that are more susceptible to interference. Just spread them out more.

Also, a NVR switch contains a coil (electromagnet). Breaking the current flow through a coil can give rise to sparking / radio interference even though this shouldn't be bad or significant with AC rather than DC.

Is your arduino in a tin box ? Do you have a decent power supply with some substantial capacitors in it, not some little USB plugtop supply ? Are your cables twisted and shielded, etc ?.

It's a classic and can be a bigger problem in industry.
Subbies coming in to do building maintenance bring a welder, they crack open a distribution board, hack it straight into a big breaker to supply the current they need and the interference from the arc scrambles the £MM 5 axis cnc that is getting it's power from the same board. Cue a few hours of downtime, possibly crashed machine, probably ruined whatever part was being cut at the time.

It's a level of ignorance akin to the guy who chopped through the great wall of China to make himself a shortcut to work.

 

[ChaiLatte]

Are your limit switches normally open or normally closed? If interference is triggering the switches, it sounds like the former. Do the inputs have pull up or pull down resistors on them so the signal line is not just floating.

Wear a thicker (turkey specification) tinfoil hat.

 

[Ollie78]

Did you use shielded cables on everything?

I wonder if an NVR is the right type of switch here. I run a spindle and vfd so not entirely sure. The the emergency stop on my cnc is not the same kind as an the NVR I have on the router table. Maybe a normal on/of switch and a seperate emergency stop is better.
My emergency stop is wired in so it stops all movement of the machine until its twisted back out and I cancel the Estop in UCCNC as well (except the spindle actually, though this is not ideal, I control it directly on the vfd ).

Can you change the activation of the switches in software ? I remember having to change some things from positive to negative activation in the machine setup bit of uccnc to get them to work right.

I have a similar problem where on occasion my tool depth sensor macro runs backwards so it goes up instead of down, only ever does it once. When I run it again its fine for the rest of the day, I cannot find out why it does it.

Ollie

 

[ChaiLatte]

...I cancel the Estop in UCCNC as well (except the spindle actually, though this is not ideal, I control it directly on the vfd)

If your E-stop is a standard 22mm industrial panel switch, you can buy another set of contacts for it and mount alongside or below the existing one. Use them in the VFD's control circuit. One mechanical switch for two control functions.

Below is just an example: on that it looks possible to mount two more blue contact sets adjacent the one shown in the picture.

https://www.switchelectronics.co.uk...tary-push-button-switch-no-ip65-yw1l-m2e10q0g
The industrial switches are very modular and have a lot of possibilites.

 

[throbscottle]

The limit switch wires are acting as antennas. Connect 1k pull up or down (whichever is appropriate) resistors to the Arduino input(s). 0.1uF capacitors connected in the other direction can also help. Ferrite beads on the wires, including the router cable, can make a big difference too. At a pinch you can cut them off old AV/computer cables.

 

[Spectric]

You don't need the NVR switch because the router is in a cabinet and under your sole control, if you are looking at safety then having an E-Stop would be much better.