Limit switches

[BobF]

I have a hobbyCNC board. It is supposed to have pullup resistors on the input pins. I have my limit switches wired in series and when I use the auto configure in Mach3, it sees each switch as it is tripped. If I leave the switches in the config, Mach3 says a limit switch is tripped as soon as I turn it on.
What to do?
I am thinking I need to add an additional resistor.

[Greolt]

Because the pins have a pullup resistor already on them that means that the pin or input is high when at rest.

The normal way to wire your limit switches is normally closed (NC) between the input pin and ground. That brings the input or pin low when a limit switch is not activated.

Then when a switch is activated, (a limit is reached) then the switch opens and the input returns to high.

In "Ports and Pins" set the relevant input to active high. In other words leave it crossed in the active low column.

Hope that's clear.

Greg

[BobF]

Thanks Greg.
That is the way it is setup, but Mach thinks it is active when it is not. There is a selection in the ports and pins setup to do this automatically. If I use that Mach sees me trip each switch and sets the config just as you said, but as soon as I save that into the config, it says I have a limit switch triggered, when I don't.
Is there some other setting I need?

[Greolt]

On the diagnostics page is the LED lit for each of the limits? LED lit means it is active.

They should not be active until you activate a switch.

If they are not lit then it sounds like electrical "Noise" is triggering the Estop condition.

Then enter about 2000 in the "Debounce Interval" on General Config and see if that stops it.

Greg

[BobF]

Thanks Greg,
The debounce fixes it almost. It now works for about 5 minutes or so and then it triggers again sometimes. Would increasing or decreasing the number help?
What common sources of noise could do this?
Motor wiring is shielded, and some of the limit switch wiring is as well. Maybe I need to rewire limits with all shielded.

[Greolt]

Yeah take it up to 3000 and see if that stops it.

I personally prefer to overcome noise with strategically placed capacitors but as this is only limits then a high software debounce should be fine.

Sometimes simply having some physical separation of signal and motor wiring can make the difference. For example they may share one conduit.

Greg

[corrie]

Hey all,can,t seem to figure out which pin on my bob is for which axes. First off my home switches are the magnetic type and all three have three wires red,green and black. I use CNCPRO and in the software X is pin13, Y is pin 12 and Z is pin 11.On the bob I have a 10 pin connector 1 through ten starting at the top, you will see in the picture. My red wire is on-5 and my black is on-6. I assume red is power and black is ground. Pin 1 has a white wire ,pin 4 has a green wire and pin 7 has a blue wire. Comeing out of the bob the red wire is joined to all the red wires from the switches and the black wire comeing out of the bob is joined to all the black wires from the switches. This leaves me with three green wires from the switches . I,ve ried a process of elimination by putting a washer in one switch and joging any axes to see whitch one would trip and then reversing those wires but still messed up. I don,t know if this makes any sence but just cant seem to figure it out, Iv,e tried switching pairs back and forth to no avial.

[Crevice Reamer]

Hi Corrie! You can't assume that the colors mean anything. Use a volt-ohmeter to find continuity between the wires. Three wires probably means you have BOTH normally open AND normally closed contacts. The two wires that read continuity with the switch at rest are normally closed and would be the wires to use as limit switches. One of the those two wires will also show continuity with the extra wire when the switch is activated. THAT wire will be your common wire and the last wire will be the normally open "home" switch.

I hope this is helpful to you.

CR.

[corrie]

Thanks for the response, I did check for continuity but not in the way you suggest. I kinda get what you are saying though, I will try agian,thanks.