Pot or Encoder type for 7i77

Hi,

I'm in the process of designing/building a pendant for my Bridgeport mill. I'm trying to select a pot or encoder for external feed override that works with the 7i77.

Searching through the various post, it looks like a 5K or 10K linear pot should work on the analog inputs. I unfortunately purchased a linear pot with the wrong electrical taper. So I'm leaning towards encoders instead of a pot.

1st question is, what value potentiometer is best suited for the 7i77 using 24v field voltage?

2nd question is, which of the following encoders would work best for feed override? I'm planning on using the inputs 16-19 for the MPG and don't know where these would hook up.

Grayhill 25LB22-G
Grayhill 25LB10-Q

www.alliedelec.com/m/d/a0747dbb45e87014a10e75056066e0d1.pdf

Thanks!

My grayhill mechanical encoders arrived. They have a nice feel and will use these. I'm not going to use potentiometers however I'm still curious about my 1st question above.

Regarding the mechanical encoders which one should I wire up? I assume quadrature 2 bit code is easier to configure/read in than 4 bit gray code plus it uses up less wiring.

I'd like to utilize the connections on the 7i77 set aside originally for the analog in potentiometers input 0-3 as those are not occupied yet on my board. How do I configure these field inputs to read encoder channel A and B?

You cannot use the built in MPG inputs on the analog pins but you can
use LinuxCNCs software encoder component, and use 7I77 inputs as standard
digital 24V inputs ( and wire the switch common to +24V )
The switch resolution is low enough that the 1 KHz servo thread sampling rate
of the software encoder component should be OK

I just somehow lost my lengthy questions post...

Thanks for the response PCW,

Can you clarify what software mode I should be in to use my handwheel MPG 5v on 16-19 (mode3) and have the inputs 0-3 as standard inputs?
Or do I need to stay clear of 0-3 all together in mode 3? I would like to use the standard 24v inputs for this application of external feed override.

Also, do you have a hal example of what I need to add to make the software encoder work?

The modes do not affect the ability to use any inputs as standard 24V digital inputs

I dont have an example off hand of the software encoder but you can read the encoder manual page
Theres probably an example of jogwheel hal plumbing for a parallel port system which would be pretty close

PCW,

I will look into a basic PP hal config.
Another question regarding the 7i77, can I hook up my 100ppr MPG encoder open ended or differential only? I may need to save on conductors in my wiring harness. Looking at the manual, it looks like only one built in MPG input is available differential on 16-19. Is this correct?

7I77 MPG inputs are single ended only

Okay thanks. My mistake, manual says quadrature. So I can use 2 mpgs like on some of your other boards. My brain at times confuses quadrature with differential.

My electronic handwheel MPG is hooked up and working. Now I need a little help with how to implement the feed override rotary mechanical switch. I have ch A hooked up to 7i77 input 00 and ch B to 01. I can see the switch working correctly in Hal.

From PCW:

PCW replied the topic: Pot or Encoder type for 7i77
You cannot use the built in MPG inputs on the analog pins but you can
use LinuxCNCs software encoder component, and use 7I77 inputs as standard
digital 24V inputs ( and wire the switch common to +24V )
The switch resolution is low enough that the 1 KHz servo thread sampling rate
of the software encoder component should be OK

I tried adding additional encoder in the hal file but was not successful. How do I turn pin 00 and 01 into software encoder pins and connect to feed override?

Look in PNCConfig page where you can define Feef override, speeds, spindle.
There is possibility to check between MPG and switches. Check what you like.
Then define in hal, what inputs are on input of that and what are enables that functions you need.

Look this doc for help
linuxcnc.org/docs/html/examples/mpg.html
www.forum.linuxcnc.org/27-driver-boards/...mpg-on-7i77?start=20