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Parallel Port Voltage and Mach 3

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Parallel Port Voltage and Mach 3

Postby chef_geek » Sun Sep 04, 2011 9:23 pm

Mach 3 isn't swinging the voltage during jog direction change. After reading through other people's posts and trying what they did, I still haven't solved the problem...any ideas? Here is what I've tried so far.

With my BIOS set to "Normal" for the Parallel Port:
High Voltage with the Port Monitor is 3.3V
Low Voltage is 0V

With my BIOS set to "EPP" or "EPP+ECP" for the Parallel Port:
High Voltage is 4.5V
Low Voltage is 4.0V

Either of these setups Mach 3 does not change the pin voltage from High Voltage to Low Voltage after jog direction change; it just stays at the high voltage. I am reading the voltage straight out of the motherboard port. I have an option for "Enable Legacy PnP detection" in my device manager for the parallel port and I've tried that, but it didn't seem to do anything.

Yes, I have:
Enabled Port #1 and verified Hex Address shown is the same as in Device Manager
Enabled X->Z axis
Set Step Pin# to 0 for all three axises (just for verifying port)
Set Dir Pins to 2->4 for X, Y, and Z
Set Dir and Step Low Active
Set Dir and Step Port as #1

Any ideas?
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Re: Parallel Port Voltage and Mach 3

Postby kevinl » Mon Sep 05, 2011 5:55 pm

normally the signal from the parallel port & BOB are only about 2uSec wide, which would be har to see with a meter..
my #1 suggestion is verify that you have 5 volts to the stepper drivers plus side of the direction & pulse connection..
all the bob has to do is apply ground to the negative side of the direction & pulse connections on the drivers to control the stepper motor movement..
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Re: Parallel Port Voltage and Mach 3

Postby chef_geek » Mon Sep 05, 2011 6:57 pm

I was under the impression that Mach 3 would alternate the voltage from high to low depending on the direction you were moving which alerts the BOB to alert the drivers the same command. I don't think it's enough to just say the BOB would ground out the voltage since it wouldn't know when to do that if the parallel port voltage for the output pin doesn't change.
-They're not mistakes...they're features!

-The Devil is in the Details, but so is salvation.
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Re: Parallel Port Voltage and Mach 3

Postby kevinl » Tue Sep 06, 2011 2:36 pm

normally the BOB does not lenghten or shorten the width of the pulses from the computer parallel port.. on the output side of the BOB the pulses from the computer are isolated thru ipto-isolators.. the voltage path is roughly the same for both the direction pulse & the move pulse, the 5 volts goes to the drivers plus side & thru the electionic inside the stepper driver, it leaves the driver on the negative side & routed to the pin on the BOB, with the MACH3 set for "low active" it sets with an open path to ground so 5 volts should be seen at this point, the only time the path to ground happen is in short pulses with the width of about 2-5 micro seconds (.000002 sec) which is very hard to see with a digital meter.. the same thing roughly happen on the computer to BOB side, in the older computer on the parallel port the electronics were a 74ls05 or 74ls06, may memory not that good but i think these are open collector IC which again (sink current) applies ground in brief pulses.. in theory to check if the motor wiring is correct you only need 5 volts to the pulse(CW+)positive side & a wire on the negative side.. when you briefly touch this wire to the negative side of the 5 volt supply the motor should turn the 1.8 degree per touch.. for the direction pulse, no pulse is one direction and a short pulse in the negative or positive direction (low active setting)just before the move pulse to trigger the driver to turn the motor in the opposite direction.
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Re: Parallel Port Voltage and Mach 3

Postby Awesomeness » Tue Sep 06, 2011 4:40 pm

As Kevin pointed out, the break out board basically does nothing - the purpose is essentially just convenience. You can run the system without a break out board in it at all. The break out board makes it convenient to connect wires to the parallel cable (e.g. screw terminals and parallel connector on the board) - but you could wire that up together by hand. The only additional feature you're likely to get from a break out board is optical isolation of the circuits, so that power problems on one side (computer side, or drive electronics side) can not cross to the other side and damage other components.

There is a caveat to this - USB break out boards. USB break out boards shouldn't really be called break out boards - they would more correctly be called a "bridge" or something. USB boards are intelligent, and convert commands received across the USB signal into the proper pulses the drivers need to move the motors. They perform this task, in addition to the normal break out board duties, which is why they cost so much more.
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Re: Parallel Port Voltage and Mach 3

Postby chef_geek » Wed Sep 07, 2011 2:35 am

That's all great, but doesn't answer my issue at all. I'm having problems prior to the BOB. Others seem to have had this issue and I've attempted their solution, with no luck. I've tried to summarize pertinent data based on what questions were asked in previous posts. Neither my BOB nor my motors are wired yet, I'm still in the verify phase adding components to the train step by step. Can anyone lend a hand in helping me troubleshoot?
-They're not mistakes...they're features!

-The Devil is in the Details, but so is salvation.
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Re: Parallel Port Voltage and Mach 3

Postby Awesomeness » Wed Sep 07, 2011 3:24 am

Are you sure the Mach3 drivers are installed and running? You aren't using a laptop, are you?
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Re: Parallel Port Voltage and Mach 3

Postby chef_geek » Wed Sep 07, 2011 10:24 am

No, I'm using a desktop running Vista. Mach3's forum describes a few additional steps to make it run correctly with Vista. I will try those steps and report back.
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-The Devil is in the Details, but so is salvation.
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Re: Parallel Port Voltage and Mach 3

Postby Awesomeness » Wed Sep 07, 2011 1:21 pm

32bit Vista?
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Re: Parallel Port Voltage and Mach 3

Postby kevinl » Wed Sep 07, 2011 3:31 pm

have you connected the BOB to the computer with a verified 25 pin striaght thru cable, set the pulse pins
for x to 2, y to 4 & z to 6.. you dont have to have the direction pins set or wired to have the stepper motors to rotate.. wiring the BOB, computer & drivers with a set of short test leads is the best way to verify operational status of even a single driver & motor to start, i think this should be performed before attached the any motor to the CNC machine.. this make it easier for testing & troubleshooting either on one or multiple computers.. to me the computer is better for troubleshooting than a meter.. even show us a picture of this testing setup to help in troubleshooting..
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