Homing Y/A Axis Says Limit Switch Triggered

[kolias]

My new cnc was working fine, I did 3 sample cuts and all turned out perfect. Then I decided to re organize the limits wiring on my C11G BOB which were kind of “messy” and since I got just headaches.

I have a total of 7 limit switches and 4 are also used for Homing. Each limit/Estop/Probe all working good but the problem starts when I try to Home. I click in Ref X and it works good, Click on Ref Z and that works good too but when I click on Y it says “Homing Y and Slave A” and soon it finish Homing the message says “Limit switch triggered” and I can’t back out despite that the “Auto limit Override” is ON.

Another message I get instead of the “Limit switch triggered” is “Limit switch is active, solve the problem and try again”

It’s a puzzle for me because I tried re wiring the limits in every way I can think and I can’t find the solution.

Any ideas where to look for a solution?

Thanks

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[CitizenOfDreams]

What kind of a controller and breakout board do you have? If it's something like an Arduino with 5V logic inputs, then simply moving the switch cables around may cause problems.

Have you looked at the switch status in your control program? Do the switches work properly and reliably if you push them by hand?

[kolias]

The controller is ESS and the breakout board is C11G. Before re wiring the limit switches the cnc was working very good, all limits working good when I push each one including the Estop, Probe, Spindle and Homing the cnc. This means the Mach3 configuration was good and I didn’t touch anything in the configuration. I did 3 complete cuts and all were good.

That’s why I’m puzzled now, looks like one or more limits are active when I try to Home the Y axis (including the A axis which is slaved to Y). The Y axis includes one limits switch for the Y+/Home and one limit switch for the A+/Home. I checked these 2 limits and alone they work properly.

The 2 wires of each limit switch connect to 5V on the BOB and a pin number. The common of a limit switch (RED) connects to the 5V and the NC (BLK) connects to a pin number. I try to switch RED to pin number and BLK to 5V but results are the same.

[CitizenOfDreams]

If the switches work fine manually yet give you errors when the motors are moving, then you likely have an electrical noise problem. Try moving the switch wires back where they were originally (in relation to the motor wires).

[kolias]

Your solution probably is good because before starting my re wire all shielded cables from the limits their ground wire was not connected to the star point ground and during my re wiring I connected all to the star point ground like I had done for all motors.

I will try tomorrow to disconnect the limits cable ground and report the results

Thank you

[kolias]

Many thanks Citizen Of Dreams, your idea solved my problem. I could not wait until tomorrow so I went and disconnect all limits ground wires from the star point ground and Homing the cnc now it works. However on the Y after the Homing was complete the “Limit Switch Triggered” lights for both the Y and A axis was lit in the diagnostic screen but I was able to back out.

However another reason I started re wiring the limits was because I was getting occasional Limit Switch triggered or E-Stop messages while the cnc was sitting and I was not touching anything on it. Very seldom but enough to tell me that I had the ground wires from the limits cables not connected to the star ground (the star ground is where the 120VAC comes in and the ground of it I connect all the grounds from the shielded motor cables/limits.

I use cable ducts (2”x3”) to run my cables inside the control panel and I know all cable are tight together, so do you have an idea how I should ground the limits cables?

Perhaps take them to the 120VAC ground which power the 48VDC PSU?

Thank you

[kolias]

The attached snip shows at the top left of the screen the Homing of all axis is complete but there are two limit switches on the Y and A axis shown on the right of the screen which are triggered but at least I can back out my axis. Just wonder where to look for to solve this minor problem.

I reroute motors/limits wiring but when I connect the shielded ground to the star point ground and try to Home it says “Limit switch is active, fix the wiring and try again”. For now I left the ground wiring not connected,

I don’t know if the ESS has anything to do with it but reading on the web it says to install a capacitor to the limits wiring but I don’t know what size capacitor and where to connect the capacitor and besides I don’t know if it will help

Thanks

[neilw20]

My new cnc was working fine, I did 3 sample cuts and all turned out perfect. Then I decided to re organize the limits wiring on my C11G BOB which were kind of “messy” and since I got just headaches.

I have a total of 7 limit switches and 4 are also used for Homing. Each limit/Estop/Probe all working good but the problem starts when I try to Home. I click in Ref X and it works good, Click on Ref Z and that works good too but when I click on Y it says “Homing Y and Slave A” and soon it finish Homing the message says “Limit switch triggered” and I can’t back out despite that the “Auto limit Override” is ON.

Another message I get instead of the “Limit switch triggered” is “Limit switch is active, solve the problem and try again”

It’s a puzzle for me because I tried re wiring the limits in every way I can think and I can’t find the solution.

Any ideas where to look for a solution?

Thanks

Run each pair of limit switch wires back to controller and don't save wires by connecting common grounds at switches. Any common ground points should be right near/at the controller. If the wires are shielded (as they should be), only ground the shield(s) at the controller end. If wires go through metal case connectors do not connect any wires to the case of the connector. If it needs an earth wire, run it back to your single common ground, but if the plug/socket is mounted to a metal case do run a ground wire, as this can cause unexpected currents in your ground system. NEVER save a wire by running currents through metalwork cases, etc.