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Motors never reverse
08 Jun 2012 19:31 #20760
by jblain
Replied by jblain on topic Re:Motors never reverse
Andy and CNC Basher, here are some more info
I am running a different PC than the one I was running XP on. The rest of the hardware (drivers cabling power supply etc) is the same.
I did some voltmeter measurements here are the results :
With everything Idle after booting and starting EMC2, I get
XDir is at 3.38 Volts
XStep is at 3.38 Volts
The + connector is at 4.28 Volts (is marked 5 volts)
If I jog in the - (minus) direction then the motor moves well and I read
XDir @ 0.07 Volts
XStep @ 3.17 Volts because of PWM
If I jog in the + (minus) direction then the motor does not move at all and I read
XDir @ 3.38 Volts
XStep @ 3.17 Volts because of PWM
The scope traces of XDir and XStep look normal
Any ideas on what is going on here ?
Jacques
I am running a different PC than the one I was running XP on. The rest of the hardware (drivers cabling power supply etc) is the same.
I did some voltmeter measurements here are the results :
With everything Idle after booting and starting EMC2, I get
XDir is at 3.38 Volts
XStep is at 3.38 Volts
The + connector is at 4.28 Volts (is marked 5 volts)
If I jog in the - (minus) direction then the motor moves well and I read
XDir @ 0.07 Volts
XStep @ 3.17 Volts because of PWM
If I jog in the + (minus) direction then the motor does not move at all and I read
XDir @ 3.38 Volts
XStep @ 3.17 Volts because of PWM
The scope traces of XDir and XStep look normal
Any ideas on what is going on here ?
Jacques
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08 Jun 2012 19:40 #20763
by PCW
Replied by PCW on topic Re:Motors never reverse
How are the step drives wired to the breakout/parallel port?
If the step drives use a common 5V as a reference for their inputs
the 3.38V may well be marginal
That is, an OPTO isolator in the drive with one side at 3.38V and the other at 5V may well be partially on when its supposed to be fully off
If the step drives use a common 5V as a reference for their inputs
the 3.38V may well be marginal
That is, an OPTO isolator in the drive with one side at 3.38V and the other at 5V may well be partially on when its supposed to be fully off
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08 Jun 2012 19:51 - 08 Jun 2012 19:53 #20764
by andypugh
Replied by andypugh on topic Re:Motors never reverse
jblain wrote:
I think you have a 3.3V parallel port, and it has not enough oomph to power the optocoupler on the DIR pin.
(why Step works is a mystery to me, though).
I think you need a different wiring scheme. (and this is the one on my stepper drives, even with a 5V parport).
There is 5V connected to the + of the stepper drive inputs (common on 3 drives, separate on the 4th).
The drives have internal current limiting resistors.
The parallel port either goes to 0V (so current flows, opto turns on) or 5V (or 3.3V in your case) and current stops flowing.
The assumption here is that your parport is high-impedence when "on" (3.3v) and that 5V won't push significant current into it.
I think this is the only way that a 3.3V port can work anyway.
Think as the pins as switches to 0V, not sources of voltage. And bear in mind that it is current flow through the opts which matters.
Asssuming you have Optos in the drives.
See page 5 of this document (actually for my stepper drives) for an example:
www.zappautomation.co.uk/pdf/manuals/PM542%20Manual.pdf
If my theory is correct then the other PC will have 5V on the parport.
However, you haven't told us the make and model of the drives (as far as I can see) nor what (if any) BoB you are using, so don't rewire until we have checked it out.
XDir is at 3.38 Volts
XDir @ 0.07 Volts
Any ideas on what is going on here ?
I think you have a 3.3V parallel port, and it has not enough oomph to power the optocoupler on the DIR pin.
(why Step works is a mystery to me, though).
I think you need a different wiring scheme. (and this is the one on my stepper drives, even with a 5V parport).
There is 5V connected to the + of the stepper drive inputs (common on 3 drives, separate on the 4th).
The drives have internal current limiting resistors.
The parallel port either goes to 0V (so current flows, opto turns on) or 5V (or 3.3V in your case) and current stops flowing.
The assumption here is that your parport is high-impedence when "on" (3.3v) and that 5V won't push significant current into it.
I think this is the only way that a 3.3V port can work anyway.
Think as the pins as switches to 0V, not sources of voltage. And bear in mind that it is current flow through the opts which matters.
Asssuming you have Optos in the drives.
See page 5 of this document (actually for my stepper drives) for an example:
www.zappautomation.co.uk/pdf/manuals/PM542%20Manual.pdf
If my theory is correct then the other PC will have 5V on the parport.
However, you haven't told us the make and model of the drives (as far as I can see) nor what (if any) BoB you are using, so don't rewire until we have checked it out.
Last edit: 08 Jun 2012 19:53 by andypugh. Reason: Wrong page number
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08 Jun 2012 20:39 #20767
by jblain
Replied by jblain on topic Re:Motors never reverse
I tought I had attached the driver manualin a previous post, sorry. here it is.
I am not sure I still have the old XP PC I will check if it was 5 volts
regards
Jacques
I am not sure I still have the old XP PC I will check if it was 5 volts
regards
Jacques
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08 Jun 2012 20:41 #20768
by jblain
Replied by jblain on topic Re:Motors never reverse
What is BoB ?
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08 Jun 2012 20:55 #20769
by BigJohnT
Replied by BigJohnT on topic Re:Motors never reverse
Break Out Board, used to isolate the parallel port from the drives and sometimes other functions.
John
John
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08 Jun 2012 20:57 #20770
by andypugh
Replied by andypugh on topic Re:Motors never reverse
A "BoB" is a break-out-board. A board with screw-termnals and a D25 connector. Often with isolation and buffering.
It is possible that adding one might be a solution, but that would cost some money.
Looking at the manual, there is no option but to connect the device as I suggested. So that isn't the problem.
If you put your multimeter in current mode between the p-port and the DIR pin it would be interesting to measure the current in both states.
That would answer the question of whether there is always too much current to be "off" or always not enough to be "on".
It is possible that adding one might be a solution, but that would cost some money.
Looking at the manual, there is no option but to connect the device as I suggested. So that isn't the problem.
If you put your multimeter in current mode between the p-port and the DIR pin it would be interesting to measure the current in both states.
That would answer the question of whether there is always too much current to be "off" or always not enough to be "on".
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08 Jun 2012 21:03 #20772
by jblain
Replied by jblain on topic Re:Motors never reverse
I am not using a BoB. I just cut off one end of a db25 cable and connected the wires to the driver terminals.
I will measure the current tomorrow and get back to you
Thanks a lot for the support
Jacques
I will measure the current tomorrow and get back to you
Thanks a lot for the support
Jacques
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10 Jun 2012 18:18 #20807
by jblain
Replied by jblain on topic Re:Motors never reverse
Since parallel pci cards are cheap (10 $) would it just be simplest to find a good 5 volts one and just install it ?
If so, would you have any suggestions as to what card to buy ?
What would you think about this one ?
lavalink.com/products/pci-bus-io-cards/p...-pci-pci-1-port-epp/
Available as 'standard' and 3.3 v' version. I guess the standard would mean 5 Volts ?
Regards
Jacques
If so, would you have any suggestions as to what card to buy ?
What would you think about this one ?
lavalink.com/products/pci-bus-io-cards/p...-pci-pci-1-port-epp/
Available as 'standard' and 3.3 v' version. I guess the standard would mean 5 Volts ?
Regards
Jacques
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10 Jun 2012 20:27 #20808
by Rick G
Replied by Rick G on topic Re:Motors never reverse
You might want to look here...
www.linuxcnc.org/index.php/english/compo...ew&catid=18&id=18917
Rick G
www.linuxcnc.org/index.php/english/compo...ew&catid=18&id=18917
Rick G
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