Jog Pendant info on my web page

[jmelson]

I just added a little more detail on the jog pendants I made for my mills, at http://pico-systems.com/pendant.html

I have now put up the HAL files that show how to connect the switches and MPG encoder to the HAL functions that implement the jog operation in EMC2. I will add circuit diagrams of the box itself soon, but that is actually pretty simple.

Jon

[jt4897]

Hmm... very interesting. I've always wondered about setting up a pendant.

One thing I'm curious about - if I read the .hal correctly you're using digital inputs 4 through 10 for the pendant. My USC is set up using ports 4,5,6 for the Y switches and 8,9,10 for the Z switches and I remember that I had to use specific ports for the - limit,+ limit and the home switch on each axis. Was that just under EMC1? (I'm running EMC2 now)

I have a very simple understanding of the .hal file but to set this up basically I just need to send the AB output of an encoder to a couple of digital inputs and wire in a few switches. There really isn't any additional circuitry needed. It's all very simple to do (now that you've provided the .hal file). Is there any additional circuitry?

Any suggestions on what resolution encoder to use?

-John

[jmelson]

Hmm... very interesting. I've always wondered about setting up a pendant.

One thing I'm curious about - if I read the .hal correctly you're using digital inputs 4 through 10 for the pendant. My USC is set up using ports 4,5,6 for the Y switches and 8,9,10 for the Z switches and I remember that I had to use specific ports for the - limit,+ limit and the home switch on each axis. Was that just under EMC1? (I'm running EMC2 now)

I have a very simple understanding of the .hal file but to set this up basically I just need to send the AB output of an encoder to a couple of digital inputs and wire in a few switches. There really isn't any additional circuitry needed. It's all very simple to do (now that you've provided the .hal file). Is there any additional circuitry?

Any suggestions on what resolution encoder to use?

-John

Back in the old (EMC1) days, these I/O assignments were hard-coded. They are all now just general digital inputs assigned as you want in the HAL files. Since I don't actually have limit switches, I could reuse a bunch of the inputs. I only use a home switch on each axis, and use the soft limits to prevent overtravel. This has worked fine for me on two machines.

If you have a spare encoder counter, it is best to use that for the MPG dial, as it has some filtering, etc. built into the USC hardware. You need to set DIP switch #4 to OFF to enable the counter for external inputs. If you will be using 4 axes, then you could use the general digital inputs for that as well, and use the HAL software module to count encoder pulses.

To see how to use the hardware encoder counter, see
http://pico-systems.com/codes/jebport/pendant.hal
Note that in this file (for the PPMC board set) the digital inputs have the opposite polarity.
I have worked the pendant signals around the traditional home signal inputs on this one.

A 100 cycle-rev encoder provides 400 quadrature counts/rev. So, that's why there are these .000025 scale factors in the file. If you use a different encoder count, then you'd just need to change these factors. I think the detents are more important than the specific resolution, as I can count off .001 or .0001 units without looking.

Jon

[jt4897]

That's brilliant - I'll use the fourth encoder counter for the dial. I did prewire my box to be able to use a fourth axis but I haven't even bought the drive for it. That leaves me five unused digital inputs which should be enough. I could also rewire my limit switches to a single channel per axis instead of separate + and - limits and recover three inputs.

I now understand why your file was using .000025 for the parameter. I went back to look over the info at linuxcnc.org and it's all making more sense now.

I see your point about the detents - good advice. Now to go check what's in stock at the warehouse - A.K.A. eBay ;-)


thanks for the info.

[jmelson]

I see your point about the detents - good advice. Now to go check what's in stock at the warehouse - A.K.A. eBay ;-)

You are not likely to find much, I tried, and ended up buying from a new vendor from Hong Kong.

Jon