Plasma THC
31 Mar 2013 18:18 #32119
by BigJohnT
Replied by BigJohnT on topic Plasma THC
I don't have access to my plasma computer till I get the memory stick in a few days but I believe this to be a current config for my plasma with the 5i20 7i76.
John
John
Please Log in or Create an account to join the conversation.
31 Mar 2013 20:09 #32123
by Coolmo32
Replied by Coolmo32 on topic Plasma THC
Ok. Thanks for the info.
Right now I am just using the pc's parallel port with a cheap C10 breakout board from Keiling and everything is working very well. How well would it work just hooking up the THCAD card to one of the C10's inputs and using a software encoder (velocity pin) to get arc voltage? Would this cause problems at fast cut speeds because of slow response? Would it possibly work?
Right now I am just using the pc's parallel port with a cheap C10 breakout board from Keiling and everything is working very well. How well would it work just hooking up the THCAD card to one of the C10's inputs and using a software encoder (velocity pin) to get arc voltage? Would this cause problems at fast cut speeds because of slow response? Would it possibly work?
Please Log in or Create an account to join the conversation.
01 Apr 2013 00:56 #32129
by BigJohnT
Replied by BigJohnT on topic Plasma THC
I do know the THCAD card has dividers for the pulse to work with a parallel port but I don't know much about the C10 even though I used one on my plasma when I first started. At one time I used the parallel port directly I think with the THCAD...
John
John
The following user(s) said Thank You: Coolmo32
Please Log in or Create an account to join the conversation.
01 Apr 2013 01:03 - 01 Apr 2013 01:24 #32130
by PCW
Replied by PCW on topic Plasma THC
It will work but the response time will be slower than when counted in hardware,
since a low pass filter is needed to get sufficient resolution.
At a 1 ms servo thread the THCADs ~1MHz count rate gives about
10 bit resolution or about 1/3 V resolution at 300V full scale
With a software counter, if you have a 50 KHz base thread you only get about 4-5 bits
of resolution at 1 ms update rate, so you need to use the low pass filter with about a
20 ms time constant to get to a useful amount of resolution.
since a low pass filter is needed to get sufficient resolution.
At a 1 ms servo thread the THCADs ~1MHz count rate gives about
10 bit resolution or about 1/3 V resolution at 300V full scale
With a software counter, if you have a 50 KHz base thread you only get about 4-5 bits
of resolution at 1 ms update rate, so you need to use the low pass filter with about a
20 ms time constant to get to a useful amount of resolution.
Last edit: 01 Apr 2013 01:24 by PCW.
Please Log in or Create an account to join the conversation.
01 Apr 2013 02:46 #32132
by Coolmo32
Replied by Coolmo32 on topic Plasma THC
Thanks guys. That is very helpful information. I will probably order the 5i25, 7i76, and THCAD and try to get it working in another computer.
Please Log in or Create an account to join the conversation.
05 Apr 2013 21:23 #32309
by Coolmo32
Replied by Coolmo32 on topic Plasma THC
Ok. Got my 5i25 installed in another computer. I was able to get John's 'plamsa-5i25' configuration to start up in linuxcnc after removing some lines in the ini and hal files. I have an adjustable power supply connected to the THCAD-10 voltage input to simulate an arc voltage. I have a couple questions.
1) For some reason I am getting a negative 'thc-encoder.vel'. I am able to correct this with negative values for 'thc-vel.scale' and 'thc-scale.offset'. Just wondering why it is negative value. All connections to the THCAD and 7i76 appear to be correct. I tried both single ended and differential connections to the incoder inputs on the 7i76 with same results.
my hal settings:
# Set up the Encoder for the THC
setp hm2_5i25.0.encoder.00.counter-mode 1
net thc-vel-in hm2_5i25.0.encoder.00.velocity => thc.encoder-vel
setp thc.scale-offset -119500
#setp thc.scale-offset 0
setp thc.vel-scale -0.00037866834
# this might need to be adjusted
setp thc.correction-vel 0.000075
# I added
setp thc.voltage-tol 1.0
question 2) I have to set 'thc.voltage-tol' manually in the hal file. The 'Voltage tolerance' setting in the pyvcp panel doesn't seem to be working or connected.
#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol
If I remove the '#' Linuxcnc won't start up.
Also Arc 'Under' 'OK' and 'Over' lights don't seem to work or be connected in the postgui.hal file.
postgui.hal:
# THC connections
net thc-enable pyvcp.thc-enable thc.enable
net thc-voltmeter pyvcp.actual-volts thc.volts
net thc-voltset pyvcp.volts-requested thc.volts-requested
net thc-req-vel thc.requested-vel <= motion.requested-vel
net thc-cur-vel thc.current-vel <= motion.current-vel
net thc-vel-status pyvcp.vel-status thc.vel-status
net thc-vel-tol pyvcp.vel-tol thc.vel-tol
# connect the arc ok indicator
net start-motion-input => pyvcp.arc-ok
#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol
# MDI commands
# rapid to home button
net remote-rapid-home halui.mdi-command-00 <= pyvcp.rapid-to-home
Appreciate any info.
1) For some reason I am getting a negative 'thc-encoder.vel'. I am able to correct this with negative values for 'thc-vel.scale' and 'thc-scale.offset'. Just wondering why it is negative value. All connections to the THCAD and 7i76 appear to be correct. I tried both single ended and differential connections to the incoder inputs on the 7i76 with same results.
my hal settings:
# Set up the Encoder for the THC
setp hm2_5i25.0.encoder.00.counter-mode 1
net thc-vel-in hm2_5i25.0.encoder.00.velocity => thc.encoder-vel
setp thc.scale-offset -119500
#setp thc.scale-offset 0
setp thc.vel-scale -0.00037866834
# this might need to be adjusted
setp thc.correction-vel 0.000075
# I added
setp thc.voltage-tol 1.0
question 2) I have to set 'thc.voltage-tol' manually in the hal file. The 'Voltage tolerance' setting in the pyvcp panel doesn't seem to be working or connected.
#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol
If I remove the '#' Linuxcnc won't start up.
Also Arc 'Under' 'OK' and 'Over' lights don't seem to work or be connected in the postgui.hal file.
postgui.hal:
# THC connections
net thc-enable pyvcp.thc-enable thc.enable
net thc-voltmeter pyvcp.actual-volts thc.volts
net thc-voltset pyvcp.volts-requested thc.volts-requested
net thc-req-vel thc.requested-vel <= motion.requested-vel
net thc-cur-vel thc.current-vel <= motion.current-vel
net thc-vel-status pyvcp.vel-status thc.vel-status
net thc-vel-tol pyvcp.vel-tol thc.vel-tol
# connect the arc ok indicator
net start-motion-input => pyvcp.arc-ok
#net thc-volts-tol pyvcp.volts-tolerance thc.voltage-tol
# MDI commands
# rapid to home button
net remote-rapid-home halui.mdi-command-00 <= pyvcp.rapid-to-home
Appreciate any info.
Please Log in or Create an account to join the conversation.
06 Apr 2013 00:37 #32314
by PCW
Replied by PCW on topic Plasma THC
Don't know about the signal issues (probably need JT to help with that), but the negative scale issue is because the THC uses an encoder counter velocity signal to read frequency. The encoder counter is set in up/down mode (A input = count, B input = up/down) the default high state on the unconnected B input makes the counter count down rather than up, causing the velocity to be negative, You can fix this as you did, or by setting the encoder scale to a negative number (or setting the encoder 'B' pin to TTL mode and grounding the B pin)
The following user(s) said Thank You: Coolmo32
Please Log in or Create an account to join the conversation.
06 Apr 2013 05:58 #32329
by Coolmo32
Replied by Coolmo32 on topic Plasma THC
OK. That makes perfect sense. I didn't think about B being the signal for up/down. So in differential mode would you need to make B+ low(ground) and B- high(+5v)? Or is differential mode even necessary? It's supposed to have more noise immunity.
Thanks,
Tim
Thanks,
Tim
Please Log in or Create an account to join the conversation.
06 Apr 2013 06:06 #32330
by PCW
Replied by PCW on topic Plasma THC
I would jumper the B pin as single ended and then ground it,
I would use differential on the 'A' pin (for noise immunity)
I would use differential on the 'A' pin (for noise immunity)
Please Log in or Create an account to join the conversation.
06 Apr 2013 06:24 #32331
by Coolmo32
Replied by Coolmo32 on topic Plasma THC
Ok. Didn't know you could do that. Guess that's why there are 3 jumpers.
Please Log in or Create an account to join the conversation.
Time to create page: 0.083 seconds