Limit Switch Wiring Diagram

[101]

I am refurbishing an old CNC router using a Masso G3 controller. Each axis has an existing pair of mechanical limit switches (one each end of travel) which can be wired as NO, or NC.

I am intending to rewire one limit switch NO on each axis and use these for homing x,y,z. There will be a pull down resistor on each switch.

I have attached a diagram. Could someone advise me please if this will work OK for the Masso because I don't want to destroy anything.

Thanks, David

 

[masso-support]

Hi @101

The way you have it drawn will not work.

I have attached a drawing giving 2 options. I recommend the first one using the normally closed contacts of your switches if they have them as this will make your setup fail safe in case of a wire breakage. I have also included a resistor in the run in case you accidently touch the +ve rail to the machine body and short out the power supply.

Either wiring option will work but if the wire breaks on option 2 the machine will keep moving until it crashes where option 1 will show a hard limit and stop movement until you fix the issue..

If using option one you will need to invert the input in Masso to make it show low in the normal state.

Hope this help

Cheers

Peter

 

[101]

Hi Peter,

Thanks for that, I can go for option 1 because the switches have the option to wire up either way. Would I be ok to run the limit switches for all 3 axis x y and z through 1 resistor or should I take 3 separate feeds from +ve each with a resistor?

Should I include a fuse?

Thanks for your help.

David

 

[breezy]

Quote from MASSO Support on November 9, 2019, 12:31 am

I have also included a resistor in the run in case you accidently touch the +ve rail to the machine body and short out the power supply.

Quote from 101 on November 9, 2019, 11:03 pm

Would I be ok to run the limit switches for all 3 axis x y and z through 1 resistor or should I take 3 separate feeds from +ve each with a resistor?

Should I include a fuse?

Only one resistor is necessary at the PS and all three axis can be connected to that resistor. 24v across 5.6k ohms is only going to draw 4.3 milliamps, regardless of the number axis shorted to ground. No fuse required.

Regards,

Arie.

 

[101]

HI,

Thats great thanks

David

 

[jim-in-michigan]

@breezy

This is Jim in Michigan. I was looking through the forum for help wiring limit switches to my masso. I seen the your answer to @101 about the resistor in the diagram Peter sent him on wiring in switches. I have a 12Volt power supply powering my masso, do I need the same 5k resister in my wiring? The import connection is on the masso and + on the power supply. Any help would be greatly appreciated. I am using the same type of switch as the wiring daigram Peter sent to @101.

Jim.

 

[breezy]

Jim,

Wire as per Peter's best practice diagram, same axis (both ends if installed) limit switches in series. As for the resistor any value will do (within reason), sticking to the value given just makes it easier to fault find in the future.

Regards,

Arie.

 

[keymont]

Stay above 2k ohms to be safe re: current at 12V.