Limit, Home and E Stop Switches

The CNC machine is finished. DC PS and control box put together.

Now I want to add the Limit Switches, Home and E Stop.

Where do these connect to the system?

Am using Xylotex XS-3525/8s-1 Controllers
Mach 3 Software
ECM Parallel breakout board.

Thanks
Hager

I have never seen the ecm bob but you could use the screw terminals on the xylotex board, if you cannot use the bob

Quote:

---

Originally Posted by GaryCorlew

I have never seen the ecm bob but you could use the screw terminals on the xylotex board, if you cannot use the bob

---

The EMC Limit connections are:

6 = Home
4 = Lim+
2 = Lim-

That's all the print says. Don't know what Home, Lim+ and Lim- mean.

I was looking for something like X axis 2 limits and the same for Y and Z.

Aren't any limit connections mentioned on the Xylotex boards.

Here is a link to a picture on the xyoltex site http://www.xylotex.com/PDFS.htm

Quote:

---

Originally Posted by GaryCorlew

Here is a link to a picture on the xyoltex site http://www.xylotex.com/PDFS.htm

---

Thanks Gary,
I think I understand but let me make sure.

Please review and let me know if I am in error. Don't want to loose that Magic Smoke. I am asuming I understand this.

I am using a "EMC Breakout Board" the regular one not the Optical isolated, but I am going to order one and use it as it is more protection for the PC.

JP17 (EMC Limit Connections) on the EMC board has connections from the parallel port listed as "Home", "LIM+" and "LIM-" I will use thoes three connections for the X, Y and Z limit switches.

So I won't have a HOME switch as I want limit switches on each axis for safety.

Two switches in parallel for each axis.

Below is my drawing:

Yes that looks correct to me, You don't have to worry about the magic smoke unless you grab more than 5 volts from somewhere.

Since I only have three limit switch connections on the EMC breakout board, how would it be if I were to configure the three connections in the following manner? This would free up the Home connection.

Connection one:
The two switches on the X Axis and the two switches on the Y Axis all in series.

Connection two:
Connect two Z Axis switches in series.

Connection three:
Use the third connection for the Home switch.

Would this configuration work with Mach3? Or would it be confused?

I do not understand the function of the “Home” switch. And how is it used?

Thanks
Hager

Home is where all the axes of your machine would be at 0, Most people use their home switches as limit switches, so you could have just three.

Quote:

---

Originally Posted by GaryCorlew

Home is where all the axes of your machine would be at 0, Most people use their home switches as limit switches, so you could have just three.

---

Thanks Gary,

Still foggy let me try this again.

"Home is where all the axes of your machine would be at 0" OK I understand this part.

"Most people use their home switches as limit switches, so you could have just three" Let me spell this out and see if I am getting it, don’t think I understand.

Don’t understand “just three” in your statement. Wouldn’t I need two switches on the X Axis (one at each end of the travel) wired separately back to the board and I would define one of them as Home using Mach 3. This would be done also for both the Y and Z axis’s. So I would need six independently wired switches, in this example. Or am I not understanding the number of limit switches I need?

My breakout board only supports three switches. So I don’t have the option to use six limit switches. So am I up the creek with this limitation?

Thanks
Hager

Quote:

---

Originally Posted by Mr.Chips

I do not understand the function of the “Home” switch. And how is it used?

---

Think of it as a reference position. You "home" the machine to return it to a known position. While you can set any location on your table as 0,0, home swotches give you a repeatable position which you can reference in your code. You can setup stops in an area of your machine to reference a "standard" 0,0 location. Place the home switches behind the stops, and Tell Mach their location relative to your stops. For example, if your X axis home switch is 2" behind your stops, you can tell Mach3 that when it homes the X axes, the switch is at X = -2. Then your machine will automatically know that your stops are at 0,0.

And once you have a known reference position, you can set up work offsets in the software to have multiple work "zones" anywhere on your table.

Do you have a diagram of the breakout board? A lot of people run all their limit switches in series to one pin, and each axis has it's own home switch to their own pins. It's possible to wire all the home switches to one pin, but you'll have to home each axis individually, because the software won't know which switch trips if their all on the same pin.

Quote:

---

Originally Posted by ger21

Think of it as a reference position. You "home" the machine to return it to a known position. While you can set any location on your table as 0,0, home swotches give you a repeatable position which you can reference in your code. You can setup stops in an area of your machine to reference a "standard" 0,0 location. Place the home switches behind the stops, and Tell Mach their location relative to your stops. For example, if your X axis home switch is 2" behind your stops, you can tell Mach3 that when it homes the X axes, the switch is at X = -2. Then your machine will automatically know that your stops are at 0,0.

And once you have a known reference position, you can set up work offsets in the software to have multiple work "zones" anywhere on your table.

---

I do understand "Home" and the need and use of it, just need to know how to set up the switches given my situation. I will send a drawing as you mentioned in your latest reply this may help is both get to the same point.

The "Stops" you are refering to, are then defined in Mach 3 as an imiginary point, correct?

Thanks for the patience.

Hager

No, I meant that you can set up physical stops on the machine. But you can use work offsets in your g-code for different work areas.

Quote:

---

Originally Posted by ger21

No, I meant that you can set up physical stops on the machine. But you can use work offsets in your g-code for different work areas.

---

Set up "physical stops", do you mean a physical stop attached to the cutting area or bearings to physical stop the router from going beyond that point.

I can't imagine doing that. There must be a terminology gap between what you are saying and my limited knowledge of CNC terminology.

Please clarify.

Hager

Attached to the cutting area, like a fence. On our commercial router, it has steel pins that pop up to locate the part, and drop down when the part is run. You could rout holes in your table to accept pins to locate the part. Mount the part to the table, and remove the pins. Make more sense? Or, you can just route reference lines into the table top to locate your machines 0,0.

Quote:

---

Originally Posted by ger21

Attached to the cutting area, like a fence. On our commercial router, it has steel pins that pop up to locate the part, and drop down when the part is run. You could rout holes in your table to accept pins to locate the part. Mount the part to the table, and remove the pins. Make more sense? Or, you can just route reference lines into the table top to locate your machines 0,0.

---

Oh, "Stops" to locate the part. I thought you were talking about stops to stop the cutter travle, we had been talking about physical limit and home switches limiting travle of the router, did not realise you had focused on part location.
Now I understand. Yes I do understand you want to fixture the piece to be cut in a known location otherwise you would not hit your target.

This is the next step after getting the limit and homing switches set up.

Thanks Gerry.