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  #1  
Old Sat 05 January 2008, 15:02
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
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Running 5 drives off one PMDX-122 board

How many gecko 203Vs will the PMDX-122 breakout board run?
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  #2  
Old Sat 05 January 2008, 15:23
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
J.R.,

The PMDX-122 is designed to directly connect to four stepper drivers. You can add a second parallel port to your computer and then daisy chain a second PMDX-122 if you need to control more than four stepper drivers or if you need more I/O than one PMDX-122 provides.
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  #3  
Old Sat 05 January 2008, 16:25
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
Mike on a cnc4pc C10 can you use pin 16 and 17 for the 5th drive?
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  #4  
Old Sat 05 January 2008, 19:20
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
JR,
I am controlling 5 gecko's with my PMDX-122 by sharing the x1 and x2 geckos with one output. The other outputs are solo. x1 / x2 shared, y solo, z solo, a solo (indexer)
SO, 5 on one unit is possible with the MM.
So far, so good.
Sean
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  #5  
Old Sun 06 January 2008, 00:51
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
J.R.,
I'm not familiar with the CNC4PC C10 Board. I've downloaded the manual, but it doesn't have all of the information that I need. I'm assuming that the pin numbers in the manual directly correlate to the parallel port pin numbers. But, assuming that pins 16 and 17 are connected to standard parallel port signals, assuming that you're using Gecko G203v steppers drives with a common ground signal, and assuming that Mach 3 has been configured to drive pins 16 and 17 properly, it looks like you might be able to hook up five stepper drivers to that board. Sorry for all of the hedging, but without a schematic, I'm just not completely sure how that board works. They're using standard 74245 ICs, so the signals are not being latched. My best advice would be to e-mail or telephone the CNC4PC people and ask them directly. One thing to keep in mind is that if you used pins 16 and 17 as step and direction signals, you would be limited to using pins 1 and 14 for all other Output signals.
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  #6  
Old Mon 07 January 2008, 05:43
joepardy
Just call me: Joe
 
Lebanon, OH
United States of America
Sean,

I am curious. How did you wire the x1 & x2 output off of the same output? I am assuming that you had to cross at least two wires because don't the x1 & x2 run in opposite directions?

Joe
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  #7  
Old Mon 07 January 2008, 06:01
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Be very careful about connecting two motors to one stepper driver. The coils on a large stepper motor (as compared to the little motors found in a floppy drive head assembly) are not perfectly matched. Running two motors from the same drive could easily destroy the Gecko stepper driver.

If you want to run two motors from the same step and direction signals, it would be better to add a buffer chip (like a 74AS245) and let the buffer chip feed two Gecko stepper drivers. The additional cost would be about $10 including the buffer chip and a protoboard from Radio Shack. By doing that, each Gecko would receive the same step and direction signal and each motor would have its own Gecko stepper drivers.
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  #8  
Old Mon 07 January 2008, 14:49
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Mike and others,
I want to make clear that I used 1 output to drive 2 individual gecko's. I checked with Mariss and Steve Stallings at PMDX and both assured me that this logic and the electrical separation was adequate. Although, Steve at PMDX tried hard as heck to sell me an additional PMDX-122
So far, I have run the test bench for about 7 hours without any issues. I had Mach3 endlessly cycle the "roadrunner" program for the length of a shop day to "burn" in the controller.

Let me know if I should be looking or doing something different.

Sean
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  #9  
Old Mon 07 January 2008, 15:20
J.R. Hatcher
Just call me: J.R. #4
 
Wilmington, North Carolina
United States of America
Send a message via Skype™ to J.R. Hatcher
Sean, you made it nice and clear in post #30 (now that I have gone back and read it again). I don't quite understand why I didn't get it the first time. I can't even think up a good lie right now that might make me look smarter .
But I got it now, 1 step and direction output running 2 Gecko drivers, right? Who says I aint smart. Still

Last edited by J.R. Hatcher; Mon 07 January 2008 at 15:24..
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  #10  
Old Tue 08 January 2008, 06:29
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The 74ALS245 devices, such as those found on the PMDX-122, can sink about 24mA and source about 15mA. The Gecko G203v draws about 2.5mA, so the PMDX-122 should have no problem driving two G203v stepper drivers per circuit. The Gecko G202 draws about 15mA, so only one G202 should be connected to each circuit on the PMDX-122; however, if necessary, your could build an auxilary board with a 74ALS245 to split one incoming signal into two outgoing signals.

(J.R., Don't worry about misreading a post. I've done it many times. You'll find proof of that in this forum, on the Shopbot forum, on CNCZone's forum, in the Letter's to the Editor section of the two local newspapers, and in a bunch of other places. If you only have one goof, you're doing really well. I have dozens.)
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  #11  
Old Tue 08 January 2008, 16:08
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Mike,
You hit the point nicely.
I didn't have the data on hand to verify what the sink/source current of both devices. Thus, my phone calls to PMDX and Gecko. I was told on very finite terms to only do this with the G203 series drives. You have disclosed the data behind the use.
Thanks again for having a really great "test bench and the right gear to use with it".
Sean
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  #12  
Old Tue 08 January 2008, 20:41
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
To summarise: One "channel" of a PMDX-122 can drive 2 Motors only if one also uses 2 Gecko G203V drives. Cannot use 2 G202 drives. Cannot use only one drive for the 2 motors.
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  #13  
Old Mon 02 June 2008, 09:11
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Following posts moved from another thread:

Be sure to jumper the PMDX-122 correctly for the G203v. You MUST connect terminal #10 on the G203v (Common) to Ground on the PMDX-122. The PMDX-122 must pull the step and the direction signals High when it sends step pulses to the motor.

(My PMDX-122 came jumpered from the factory ready for use with the G201 and the G202 stepper drivers, not for the G203V stepper driver. JP1 is the jumper to check.)

When wired half-coil (Black/Yellow, Red/White), the maximum voltage for the PK296A2A-SGxx motor is about 38V. If you're using a 58V power supply, you will need to wire the motors using the Black/Green, Red/Blue wires, otherwise the motors will get too hot.
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  #14  
Old Tue 03 June 2008, 22:16
shaperx
Just call me: Mark
 
San Diego,Ca
United States of America
Still no go. I was on the phone with Gecko today and did some tests. Checked voltage Term #10 on the Gecko to pin 3,5,7 and 9 on the PMDX and I have 1v or 2.5v The voltage on pins 2,4,5 and 8 1v or 2.5v when it should 0v or 5v. We check out the drivers they all work fine got the motors to spin by putting 5v to term #9 on the 203.
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  #15  
Old Wed 04 June 2008, 07:35
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Mark,

How are you providing power to the PMDX-122? I use a 12VDC power supply, others use a low voltage AC power supply.
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  #16  
Old Wed 04 June 2008, 09:31
shaperx
Just call me: Mark
 
San Diego,Ca
United States of America
My power supply has 12vdc and I tried with USB.Im sticking with the USB.
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  #17  
Old Wed 04 June 2008, 14:16
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
I've never been too successful using USB as a power source. It greatly depends on your USB. The computers that I'm using on the test bench are 2-3 years old, so they aren't the latest and greatest - that's why I use an auxiliary power supply with the PMDX-122.

If you're getting 1VDC to 2.5VDC between Terminal 10 on the Gecko and the Step/Direction signals on the Gecko, something on the PMDX-122 is not working, some wiring isn't correct, or the Mach3 settings aren't correct.

Starting with the PMDX-122, verify that jumper JP1 is in the BOTTOM position so that it jumpers GND and the center post.

With a voltage meter, verify that you have 5VDC between J5, +5V AUX OUT (or J8, +5V AUX OUT) and J1-COM, J2-COM, J3-COM, J4-COM.

Verify with a meter (resistance reading - power off) that you have a good connection between J1-COM, J2-COM, J3-COM, J4-COM and the associated G203v Terminal #10.

Check the polarity of the signals in Mach 3's setup. G203v uses Step Active Low with Red X. (G202 and G201 use Step Active Low with Green Check Mark).

(I just tried running my test setup using USB as the power source and it failed, but that may be caused by the older computer that I'm using.)
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  #18  
Old Wed 04 June 2008, 14:25
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
My PC's USB port doesn't drive a PMDX-122 either.

A 9V battery does a good job for a test though.
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  #19  
Old Wed 04 June 2008, 16:13
shaperx
Just call me: Mark
 
San Diego,Ca
United States of America
It was the JP3 Its working thanks for the help. Do you power your PMDX 12vdc off you main power supply?
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  #20  
Old Wed 04 June 2008, 16:59
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
I use a "wall-wart" power supply that is connected through the main switch to A.C. so that whenever, the main power supply is on, the auxiliary power supply is on also. (If I had a little more ambition, I would wind some magnet coil wire around the toroidal transformer until I had 9 to 12 VAC, but I have a bunch of wal-wart type transformers left over from others things.)
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  #21  
Old Wed 04 June 2008, 18:27
shaperx
Just call me: Mark
 
San Diego,Ca
United States of America
My power supply has a 12vdc output. Steve at Pmdx thinks thats a bad way to go if you Estop you lose power to the board. The USB keeps it powered. It sounds right to me. What do you think.
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  #22  
Old Thu 05 June 2008, 03:13
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
Mark,
I agree with Steve. On a technical level, it's better to have the E-stop switch(es) cut the pulse train that goes from the breakout board to the Gecko stepper drivers rather than just killing all power to the system. Cutting the pulse stream is less abusive to the entire power supply. However, cutting all power via the E-stop switch is safer from a safety point of view.

On my test bench, the On/Off switch turns on the 12VDC unit so that the PMDX-122 is powered up. The stepper power supply also runs from the On/Off switch, but its source is also routed through a latching contactor, which means that I have to momentarily press an On switch to cause the contactor to latch. By doing that, I can be certain that the PMDX-122 is on and that Mach 3 is up and running before I energize the steppers.
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  #23  
Old Thu 05 June 2008, 03:51
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
My thought process on the e-stop logic is as follows:

- It is important to cut the pulse stream for an e-stop because the power supply capacitors take a while to discharge (motors will still want to turn if they still get pulses).

- Cutting power to the PMDX-122 should put it into a safe mode.

I don't see the reason for maintaining power to the PMDX?
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  #24  
Old Thu 05 June 2008, 06:05
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
The PMDX might be driving other critical things that need to stay on even if the steppers are suddenly stopped. For instance, if a vacuum clamping system were controlled by the PMDX and the router/spindle were manually controlled (not by the PMDX), then if the PMDX shut down, parts could go flying before the router/spindle could be turned off.
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  #25  
Old Thu 05 June 2008, 06:43
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
My approach is "one button kills all". Yes, if somone has a more complex logic in the E-stop process, then the the logic provider must be kept alive.
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  #26  
Old Thu 02 October 2008, 09:05
javeria
Just call me: Irfan #33
 
Bangalore
India
is the pmdx able to handle all 4 axis + the spindle

there will be a total of 5 step dir signals reqd. and another for the analog I think.

I am just lazy to do more research - just looking for a answer straight.

RGDS
Irfan
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  #27  
Old Fri 10 October 2008, 13:15
vishnu
Just call me: vishnu
 
Coimbatore(TN)
India
Is it possible to set up a 4'th rotary axis using the PMDX-122 board itself or should i get a extra bob to couple them.

Vishnu
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  #28  
Old Fri 10 October 2008, 13:41
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
You could theoretically drive a pair of G203V's, for your x-axis, off one "channel" of the PMDX-122. (The PMDX-122 user manual says it can sink or source 16mA, each G203V needs about 2.5mA). The only downside is that you would not be able to auto-square the gantry.
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  #29  
Old Fri 10 October 2008, 14:40
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
Gerald,
How usefull is the autosquare function? Is it something you find usefull or needed in your experience?
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  #30  
Old Fri 10 October 2008, 15:20
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Have not needed it, or even considered it for our machines. Our squaring is done once mechanically (with shim washers behind the v-rollers) and the machine happily maintains that square from day to day. If in doubt, then we run it to the stops to check.
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