Do I need a resistor when adding a touch plate (probe) to Mesa 7i76e?

I am adding a probe to my z-axis and am wondering if I need to add a resistor to the input side? I am using the Mesa 7i76e ethernet card. I found the following page online that mentions a "2k pull up resistor". Have not read it anywhere else. So thought I would ask if others here have done this.

Run a wire from the +24vdc field power terminal, TB1 pin 4, through a 2k pull up resistor to the input pin, TB5 pin 10.Run two wires to the touch off plate. One will be hardwired to the DC Ground in the electronics box and have an alligator clip or magnet to attach the wire to the cutting tool or spindle. The other wire from the probe should run back to the input pin on the 7i76e, TB5 pin 10.The input can be inverted in the software by adding “-not” to the input number.

Source:  www.diycncdesign.com/linuxcnc-2.8-touch-plate-probe.html

Thanks

Ok so not sure why my search did not come up with more answers before, but it appears that I do need a resistor after all.

Thanks

Yes you do!

Have a look here : www.forum.linuxcnc.org/27-driver-boards/...late-short-to-ground

Thanks for that link. I notice in the diagram that was post the touchplate positive wire is using pin 01 which is an analog input.
 

In this blog he uses pin 10 which is a digital input. 
www.diycncdesign.com/linuxcnc-2.8-touch-plate-probe.html

Which is the correct input to use?

Shawn

I am a little fuzzy on the setup in LCNC. I tried following the instructions on that page I linked in my previous post but when I got to installing the Probe Screen application it gets a little unclear. Is there a dumbed down or more clear step by step installation process for this somewhere?

Do I have to install Probe Screen? I read another post somewhere that they installed a macro called touch_plate_z.ngc instead. What is the easiest/best way?

I found these instructions from JohnnyCNC on how to setup his Touch Plate w/Button. I have read through it and am thinking that maybe I could alter it to work but instead of triggering the Touch Off from a button on the touch plate but instead add a button to the Axis GUI to trigger it. 

Is my thinking correct? Or am I way off base and need to go a different route? 

JohnnyCNC post=158477 userid=23695
Other info you might want.

I have a button on my homemade touch-plate and this is how I made the connections in the hal file to debounce the signal when the bit touches the plate and recognizes the button press to start the probing process.

This is how I have the debounce setup on my probe. My touch-plate has a spring loaded contact surface and a button to start the probe process. The code below is placed in a file named 100.ng and the file is placed in the folder where you G-Code files are.

#limits debounce to stop false triggers
loadrt debounce cfg=2,1 #change to the number you want
setp debounce.0.delay 100 #this sets the delay 100 iterations of the servo-thread
addf debounce.0 servo-thread

net deb-probe-in debounce.0.0.in <= hm2_5i25.0.7i76.0.0.input-05-not  Touch plate contact surface.
net probe-in debounce.0.0.out
net probe-in => motion.probe-input
net run-touch-btn <= hm2_5i25.0.7i76.0.0.input-06 => halui.mdi-command-04  Physical probe start button.

This is the code that is run when I press the button on my touch-plate. I found this on the web but I don't remember where. Probably on this forum. Place this code in a file name 100.ng and place the file in the folder where your G-Code file are.

<pre>
o100 sub
G20
( Set current Z position to 0 so that we will always be moving down )
G10 L20 P0 Z0
( Probe to Z-.5 at F2 [Uses machine units, I work in inch, this is meant to be slow!] )
G38.2 Z-.25 f2
( Set Z0 at point where probe triggers with offset of +1.0095 [this is the thickness of my touch plate. You must adjust this for your plate / setup] )
(G10 L20 = Set Coordinate System // P - coordinate system 0-9 0 = Not active)
G10 L20 P1 Z1.0095
( Rapid up to Z.5 above the material )
(G10 L20 P1)
(Use machine coordinates)
G90
G53 G0
(Incremental mode)
G91
(Rapid Z up 1 inches)
G0 Z1
o100 endsub
</pre>

Sray69 wrote:

... I notice in the diagram that was post the touchplate positive wire is using pin 01 which is an analog input.
... In this blog he uses pin 10 which is a digital input. ... Which is the correct input to use?

 

The 7i76 support 3 software mode. In mode 1 & 2 you have 4 analog inputs but in mode 0 you don't have any. The diagram is probably for mode 0.

You can use any digital input. Just edit this line:
          net probe-in     <=  hm2_7i76e.0.7i76.0.0.input-25-not
to use the input you want to use.
 

Sray69 wrote:

Do I have to install Probe Screen? I read another post somewhere that they installed a macro called touch_plate_z.ngc instead. What is the easiest/best way?
 

I think the easiest way is to go with gmoccapy screen since touch probe (for tool setting) is integrated. See here: linuxcnc.org/docs/html/gui/gmoccapy.html...uto-tool-measurement


 

Sray69 wrote:

I found these instructions from JohnnyCNC on how to setup his Touch Plate w/Button. I have read through it and am thinking that maybe I could alter it to work but instead of triggering the Touch Off from a button on the touch plate but instead add a button to the Axis GUI to trigger it. 

Is my thinking correct? Or am I way off base and need to go a different route?

 

I'm sorry, can't help you much about this since I'm not even using the 7i76.  I can only suggest to first try it the way it is to make sure it's working as expected. Then come back here and ask about what needs to be done or what you tried to make it work the way you want.

 

I was able to get the touchplate installed and working by following this guide. I ended up switching to Gmoccopy because it already has a Z touch plate function/button available. 

wiki.printnc.info/en/controllers/linuxcnc/ztouchplate