Fast Hole EDM from Hacked Parts

EDM is very noisy and may have voltage spikes on the "ground" 
that exceed the +-25V peak limitations of the 7I96S encoder
inputs.

Since it appears the you did not connect the grounds together there is
opportunity for these spikes to damage the 7I96 inputs. It may well be OK
but the way is was connected could not work.

I think you misunderstood the PWM output. It does no appear to be
a differential signal, so must connect to PWM --> IDX+ and GND --> GND

The frequency pin should show the current PWM frequency
The valid pin is true when the PWM frequency is above the
minimum frequency (basically a fault indication)
 

PCW,

Okay, lets hope nothing is fried.  I will go try the outputs of PWM freq and valid now and report back.

I got a chance to spend some time with the oscilloscope today am getting interesting behavior out of the EDM supply.  What I am seeing is a sine wave that has an amplitude of about .5v. This entire sine wave moves up and down depending on the intensity of the EDM cut.  At no cut it is at 0 volts and at short it is at 3.3v.  In other words it seems to be behaving like an analog signal. It seems to me that will not work with the periodm func in mesa.  I have contacted the creator of the Powercore EDM to see if this is the correct behavior or if something was damaged. 

My alternative plan is to use an arduino that I have here to take the analog input and send it to the computer via USB to monitor cut duty cycle. Hopefully the python script that I am writing can accommodate communication with the arduino. 

 

The freq pin is 0 and the valid pin is false.  So it appears that there is an issue with the PWM measuring. 

Hi all,

I have given up on trying to have a PID control of the feedrate.  Instead I am using an arduino to set an input pin (hm2_7i96s.0.inm.00.input-10) to TRUE when the signal from the EDM power supply shows a short.  I am able to confirm the pin is going TRUE using hal meter.  That is the extent of my success. 

I am trying to use this pin to set the feedrate into reverse when a short is detected using motion.adaptive-feed. However, absolutely nothing I do will work.  I was trying to do this inside of the .hal file and that did not work. I also tried to do it in a python script and the GUI refused to load when this was attempted. 

I really have no idea how to program linuxCNC and I am growing a little desperate and could really use some help. Could someone please walk me through how to use the input pin hm2_7i96s.0.inm.00.input-10 to toggle feedrate from forward to reverse.  I feel like this should be straightforward but I am seriously struggling.

Thank you,
-Dylan

Hi Tommy,

Thank you for the response.  I am not sure what is obvious right now. The pin I am trying to use is motion.adaptive-feed which is what Aceira suggested.  From the motion page it seems that when this pin is set to 1 the feedrate is what was initially set.  Then this value can be scaled.  Its a multiple.  So to reverse feedrate at the same velocity in reverse this pin should be set to -1. 

This is how I understand it but could be wrong.  But I just don't know how to do this. 

Tommy,

Maybe you were good luck, but I got it working.  It may have been a syntax error.  Or maybe I didnt make the python file executable.  But what matters is that the feedrate will reverse now.  Thank god. I can even control it with the arduino.  Tomorrow I will do a test cut. 

Best,
-Dylan