Author Topic: PMDX and clearpath in Test mode  (Read 120 times)

OldePhart

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PMDX and clearpath in Test mode
« on: February 02, 2019, 07:49:36 PM »
I bought the pmdx-126 and a smoothstepper and am wiring it up today.  I have a single motor hooked up, enable works as indicated by the clearpath LED changing color, and I can see the step and direction LEDs lite up when I enter the boards test mode and hold the button down. But the clearpath doesn't move.  Moves fine under clearpath software (USB connection).  is there an incompatibility with the test signal and the clearpath? Other ideas?

OldePhart

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Re: PMDX and clearpath in Test mode
« Reply #1 on: February 02, 2019, 09:08:56 PM »
Might be on to something, 3.8V drive signals. I wonder if thats below the threshold of the Clearpath motors. the +5 rail (PC+5v) on the 126 is +5v but step and direction are low.

12strings

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Re: PMDX and clearpath in Test mode
« Reply #2 on: February 02, 2019, 11:25:43 PM »
If you see the step/dir indicators turn on and off in the ClearPath software while connected via USB (I presume that is where you saw them), then the levels coming out of the PMDX-126 are sufficient.  The one random ClearPath users manual I found says the ClearPath units need to be driven with a source capable of supplying 8mA at 5V.  The PMDX-126 can supply that, though as you've seen not necessarily at 5V - the higher the current draw, the more the output voltage can droop.

If that worries you (I wouldn't be concerned) - then change your wiring so the PC+5V from the PMDX-126 goes to the ClearPath "+" terminal and the Step or Dir output goes to the "-" terminal.  Not that this will invert the effective polarity of the step/dir signals.

But back to your original issue - the obvious question is have you configured the ClearPath to use the inputs as step and direction?  This looks to be direction on input "A" and step on input "B".  If so, how many pulses per revolution do you have it configured for?  Are you sure the PMDX-126 test mode is outputting step pulses on the terminals that you have connected to the ClearPath Input B.  When you press the PMDXD-126 test button the have it generate step pulses, do you see the "Step"/Input B indicator on the ClearPath s/w toggle?  There is a DIP switch on the PMDX-126 that determines which pins the PMDX-126 outputs the test step signal on.

Post you exact wiring from the PMDX-126 to the ClearPath, and the exact PMDX-126 DIP switch settings.

OldePhart

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Re: PMDX and clearpath in Test mode
« Reply #3 on: February 03, 2019, 12:56:23 AM »
Hey 12, thanks for the reply.

I don't see the signals in the clearpath software, I see nothing there. But the drives work fine using the MSP software. 

What I see is that the LEDs on the PMDX board are blinking as I would expect, DIR coming on and off with each press of the test button and STEP barely illuminating and getting more intense as the pulse train ramps up.

I looked at these signals with a scope looking for pulse duration and better see what was actually happening and thats when I saw the low volt signal. I understand that excess current would drag the signal down, but as you said the board should be able to provide what the Clearpath requires and other folks have this working.

I don't have a current probe for this scope so I can only read the DIR signal's current with a meter, I can do that tomorrow. FWIW I did reverse them with the config dip switches and the results were the same. Its also of note that the PC +5v pin is fine the whole time.

The Clearpath motor is set for Step and Direction -doesn't appear to have any other options available, they are greyed out in the software. I never saw any way to tell it what signal types to look for but I was hoping there was such an option in there somewhere.

Set for 800 Pulses per rev, as delivered.

Config switches are set per switch table, the pulse train occurs when it should and direction toggles properly as well, its just that the voltage is too low.

I'm not following what you mean by using the PC+5V to the Clearpath + etc.

OldePhart

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Re: PMDX and clearpath in Test mode
« Reply #4 on: February 03, 2019, 12:20:40 PM »
Brown, Yellow Org, Red to Gnd (Neg side of all)
Black (InputB) to J4-2 (Step)
White (InputA) to J4-3 (Dir)
Blue (Enable) to PC+5V - motor LED responds to this signal
Green (HLFB) floating - gotta work out the rest first

12strings

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Re: PMDX and clearpath in Test mode
« Reply #5 on: February 03, 2019, 11:47:52 PM »
First - I don't think the voltage droop to 3.8V is significant, but I could be wrong.  What matters is that there is enough current flowing into the ClearPath to activate its opto-couplers.  The PMDX-126 electrical specs say the output voltage may be as low as 3.8V at max current output.

Just to verify - when you say  brown, yellow, etc. to "Gnd", do you mean the "PCgnd" pins on the PMDX-126 J1 through J4?  Or do you mean the "GND" terminals on J12 and J13?

You currently have the the PMDX-126 outputs connected to Input A/B+ and input A/B- to GND.  This requires the buffers on the PMDX-126 to source current into the ClearPath inputs.  An alternative is to connect the PMDX-126 PC+5V to input A/B+ and connect Input A/B- to the PMDX-126 outputs (J4 pin 2 and 3).  This sources the current from the PMDX-126's power supply and sinks current in the PMDX-126 outputs.  There should be a diagram of this type of connection in your ClearPath manual.  You may get a higher voltage across the ClearPath +/- pins with this method.  But doing so effectively inverts the step pulse from the PMDX-126.  So if/when you get the motors running and move on to (I presume) Mach, you should configure the step as "active low".  That doesn't matter for the PMDX-126 test mode.

Try this - connect the ClearPath "InputA-" to the PMDX-126 PCgnd on J4.  Then connect the "PC+5V" from J4 to the "InputA+" terminal on the ClearPath.  Does the ClearPath software show that input active?  Disconnect the "PC+5V" from the ClearPath.  Does the ClearPath software show any change in that input?  Try the same test on the "Input B" terminals.

Are you sure there is no configuration in the ClearPath software that disables the step/dir inputs when controlling the device via USB?   Is there some kind of override when using the software?  Are you sure the ClearPath is configure for step and direction and not some other mode (I don't know what without looking at a ClearPath manual).

OldePhart

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Re: PMDX and clearpath in Test mode
« Reply #6 on: February 04, 2019, 10:28:10 AM »
Should have clarified that, motor is wired to PCGnd on the same connector as drive signals. That kind of screwup would have taken extra effort since the different grounds aren't even on the same side of the board, But I can't blame you for asking :) 

I see where you are going by moving the signals around and I will poke at that when I measure the current being drawn.  I see in the PMDX docs that expected the signal should be " At Least" 3.8 V so I think this is by design and might be incompatible without a kludge. If I have to build a follower circuit to bring the signal level up to proper spec, I will have to re think the PMDX.

I have a call into Teknic as well to see if I can expect to see signal inputs in their software as well as other ideas about this.

12strings

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Re: PMDX and clearpath in Test mode
« Reply #7 on: February 04, 2019, 09:45:39 PM »
I would run the test from the next-to-last paragraph in my previous post even before you try to measure the current.  The test I described will prove whether the voltage you are seeing on the PMDX-126 outputs is a red herring.  Use the PC+5V and PCgnd connected directly to the ClearPath +/- inputs (for example, to InputA+ and InputA-).  After connecting these, measure the voltage across the +/- terminals - it should be very close to 5V.  If so, and the ClearPath software doesn't show the input changing as you connect/disconnect the PC+5V, the problem is not the PMDX board.

One more thing to try, and I don't think this is you issue, but it is a quick test - put your meter on AC volts and measure the PC+5V to PCgnd on one of the PMDX-126 connectors.  You should see some very small levels (miliivolts perhaps?).  If you see a large AC voltage then there may be something wrong with the PMDX-126.