3 Servos and 1 Stepper on a 7i77 +5i25
05 Nov 2014 05:58 #52786
by andypugh
I think that those pins are likely to only be powered when there is a USB cable attached. They seem to be labelled as PC power, not external power.
Replied by andypugh on topic 3 Servos and 1 Stepper on a 7i77 +5i25
Am I naive to expect that I should be seeing 5V on the PC5V header (lower right)? The BOB has a power LED light on but the 5V header reads 0.9V relative to the gnd marked 'common cathode'
I think that those pins are likely to only be powered when there is a USB cable attached. They seem to be labelled as PC power, not external power.
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08 Nov 2014 09:53 - 08 Nov 2014 09:56 #52926
by sliptonic
Replied by sliptonic on topic 3 Servos and 1 Stepper on a 7i77 +5i25
I'm finally getting close. Turns out this card is kind of a P.O.S. That USB connector is a Type A female. To connect it to a PC, you need a A male to A male cable. Try to find that!
Anyway, I have the axis turning but still getting following errors. This is open loop so I must have something off in my calculations but I don't see it. What looks wrong here?
8 microsteps. 1:3 ratio. 200 steps/rev. gives me a scale of 13.333
Anyway, I have the axis turning but still getting following errors. This is open loop so I must have something off in my calculations but I don't see it. What looks wrong here?
8 microsteps. 1:3 ratio. 200 steps/rev. gives me a scale of 13.333
#********************
# Axis A
#********************
[AXIS_3]
TYPE = ANGULAR
HOME = 0.0
FERROR = 0.050
MIN_FERROR = 0.020
MAX_VELOCITY = 1100.0
MAX_ACCELERATION = 2200.0
# The values below should be 25% larger than MAX_VELOCITY and MAX_ACCELERATION
# If using BACKLASH compensation STEPGEN_MAXACCEL should be 100% larger.
STEPGEN_MAXVEL = 1400.0
STEPGEN_MAXACCEL = 2700.0
# these are in nanoseconds
DIRSETUP = 5000
DIRHOLD = 10000
STEPLEN = 2500
STEPSPACE = 2500
STEP_SCALE = -13.3333
MIN_LIMIT = -9999.0
MAX_LIMIT = 9999.0
HOME_OFFSET = 0.0
Last edit: 08 Nov 2014 09:56 by sliptonic.
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08 Nov 2014 21:15 #52947
by BigJohnT
Replied by BigJohnT on topic 3 Servos and 1 Stepper on a 7i77 +5i25
For ideas about following errors with stepper drives see this chapter in the manual.
linuxcnc.org/docs/html/common/Stepper_Di...tml#_following_error
JT
linuxcnc.org/docs/html/common/Stepper_Di...tml#_following_error
JT
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08 Nov 2014 23:11 #52952
by PCW
Replied by PCW on topic 3 Servos and 1 Stepper on a 7i77 +5i25
One other source of following errors in stepper systems is excessive servo thread latency
also, your ferror settings may be a bit optimistic since you have a step size of 0.075 degrees
also, your ferror settings may be a bit optimistic since you have a step size of 0.075 degrees
The following user(s) said Thank You: sliptonic
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