Machsupport Forum
Mach Discussion => Mach3 under Vista => Topic started by: ShiftNL2 on January 08, 2021, 10:33:00 PM
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I've been working on fixing up an old Bridgeport Boss w/ CNC retrofit, and in the process changing from TurboCNC to Mach3. We're very close, on an oscilloscope we have Mach3 giving 0.6v Lo Dir signals, and 3.4v Hi Dir signals. For Step we get 3.4v with a 5us pulse downwards, which is what we need for our Larken Cobra Stepper Drivers.
The issue I'm trying to figure out is why we are getting 3.4v Hi signal outputs and not 5v signal outputs. We are using the A25 from CNC4pc, a 5v PCI-Parallel Port card, on a 32-bit 5v PCI rail. We get a 5 volt signal from all of our Status/Control pins on the parallel port, but 3.4v on all of the Data pins. Is this something caused by Mach3 as it controls the outputs of the Data pins? ATM our motor does not step, but makes a slight humming noise constantly, I believe the stepper drivers expect a 5v Step signal.
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To add some more info to this:
http://www.viperservo.com/dloads/L-3axis.pdf
Page 6 of this shows the expected Step/Dir waveforms, I do get these exact waveforms shown on my oscilloscope, which is why I believe voltage is the issue. At the moment I am just trying to get the X axis to jog, I have the Y/Z boards disconnected.
There is a green LED on the board, when the board is receiving a step signal, it turns off. Something to note is that when I step Mach3 to step/dir on pins 2/3, it is constantly off and the stepper motor is making a constant slight humming noise, but not stepping.
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Unfortunalely, not all parallel port cards are good.
My suggestion would be to replace the parallel port card with a known good 5 V outputs card. This thread may be helpful; https://www.machsupport.com/forum/index.php?topic=34848.0
Tweakie.
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just for crosscheck, try to measure the voltage without connected stepper controller.
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I don't see a mention of a breakout board. The parallel port board may not be able to supply the current needed to drive the stepper driver opto coupler inputs. Most BOB boards have buffers on the outputs.