Hi Guys,

I'm needing some clarification on the correct way to set up Home switch connections for Mach 3.

I am using a Rutex 2120 motherboard which appears to have nothing allocated to pins 18 through 25 (listed as pc ground). Can I use any three of these circuits by cutting the wires in the DB25 lead, adding in the switches and then splicing the other terminal of the switch to a 5 volt power supply? Where is the most appropriate place to tap into 5 volts to power the Home circuits?

Cheers
Splint

Splint

Pins 10 to 13 and 15 are inputs.  You need to use these.

Unless you have two printer ports then there are more options.

Greg

No!!
The pin outs for LPT1 (printer port) are as follows -
pins 2 - 9  address &H378 (Out)
pins 1,14,16,17 - address &H37A (Out)
pins 10,11,12,13,15 - address &H379 (Inputs)

pins 18 - 25 are the signal ground wires for the above - i.e. they are connected to 0 volts on your computer, you must not cut them or the computer will have no reference.

I don't know what method you are using for your home switches - but the simplest way to do it is, perhaps, micro switches.
a) decide which three input pins you are going to use.
b) select one of the ground wires - or if it is easier, select three, one for each switch.
c) fit your home switch so that, when you go home, the switch closes, and makes a connection between the signal ground and the input wire.
d) identify these input wires in Ports and Pins/Inputs and show them as active low.
You do not need to use a 5 volt supply, because the input pins are already pulled high internally in the computer.
You can test them by switching them manually and looking of the diagnostics page.

You can test the principle of this even more simply, before you mess about with your lathe/mill by selecting an input pin, fasten a wire to it and then touch it on any of the ground terminals. If you have identified this in port and pins/inputs, then you should see the led light on the diagnostics page.

I have just connected mine this week, as above, and they work perfectly, and even with cheap micro switches, they are accurate to 2/10,000 of an inch - which is good enough for me. I could get some more expensive switches which are probably more accurate. The way it works is the carriage runs down until it closes the switch, then it backs off slowly until the switch opens again - it seems very accurate.

The problem will be if you have already used your 5 input wires for anything else, say limit switches. I'm afraid that, if you have, you will have to fit some sort of second port - and then carry on as above. You can, however, combine home switches with limit switches if that is convenient, which saves inputs.

 

Thanks for the replies guys,

I will be using small micro switches for both limit an homing. I had a look over the R21X0.pdf file which lists pins 10,11,12,13 and 15 as E-stop, X,Y,Z and A limit inputs. There is nothing else available as inputs short of adding in a second LPT port.

Just as a passing thought, would it be realistic or possible to to have E-stop on pin 10, X,Y and Z limit switches wired in series and run through pin 11 and X,Y,and Z home switches run through 11, 13 and 15 respectively?

I'll do a bit more reading about combining home and limit switches.

Cheers
Splint

Yes that would be a quite common way of doing it.

Greg

Here is a simple schematic that I got off of CNC Zone.
It helped me alot when I was coverting my Knee Mill
olf20

Thanks Olf20, that seems to be what I'm looking for.

Splint

Hi, Splint

Simplicity is best sometimes.

In Homing Mode, Mach Homes one axis at a time, It's just looking for a Switch to open, It nows which axis is moving and changes it's direction to move the axis off the switch, After all axis's are homed.

Mach reverts to Limit Mode, Again just looking for a switch to open seeing the over limit.
 
Mach can use just 3 switches to accomplish the Home / Limit function with only One Input Pin used.

Wire your Switches in Series and  Common (C), Normally Closed (NC) terminal's.

Just some Thought's, Chip