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Author Topic: Connecting an MPG to Mach3  (Read 7723 times)
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rogerbsstt
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« on: December 21, 2008, 05:18:25 PM »

Gentlemen,
I have recently obtained an MPG that I have been trying to connect to my Mach3 / mill. The unit is a HEDS-5700 C10 optical encoder. with 100CPR and 5v input.I have wired the unit up as per the tech data for the unit, and have tested the wiring to show that A & B outputs indicate 5v pulses when the wheel is turned.
I have connected the input wiring 5V and grd to the power connections on my CNC4PC  C10 breakout board (as per their wiring diagram), and have connected the output A & B wires to pin nos 13 and 15 on the board. In Mach 3 I have enabled MPG#1, selected port no 1, pin no 13, then port #1, pin no 15, I have left the steps set at 2 (as indicated for 100CPR in the Mach3 manual), and the velocity to 100.  I have used the Tab key to bring up the jog/mpg screen, set jog to MPG,
 selected Step/velocity for jog type, and axis 1 to X.  When I turn the wheel I get no response. When I go to the diag screen and move the wheel no leds light up in the pin status. When I checked the voltage on the pins 13 & 15 while they where disconnected from the breakout board I got 4.86 volt signals from the A & B wires, but when they were connected to the breakout board the max signal was .8 volts. After stumbling across the calibration screen for MPGs in Mach3, when I run through the process, all the settings came back 0. I assume it is because Mach3 is not getting a reading from the MPG, but as I can get a 5v signal out of the unit, I cant see what is wrong, and as I'm not exactly an electrical genius, cant figure out what I have missed. Please can you offer some help as I really want to use this unit on my mill.  THANKS for any assistance.  

A SAFE and happy holiday to all.
 rogerbsstt
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Hood
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« Reply #1 on: December 21, 2008, 05:23:12 PM »

Doesnt sound like you have missed anything but rather for some reason the signals are not passing through the BOB. Where were you measuring the voltage when connected to the BOB, was it at the MPG connection side of the BOB or the computer side?
Hood
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rogerbsstt
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« Reply #2 on: December 21, 2008, 06:57:34 PM »

Hood,
thanks for your fast reply,

I measured the voltage from the BOB  13 & 15 pin connection screws. Perhaps I should try two other pins??
Thanks

rogerbsstt.
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Hood
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« Reply #3 on: December 21, 2008, 07:06:01 PM »

Kind of sounds like the voltage is getting pulled down on the BOB, I am not great with electronics but certainly sounds that way. Do you have a second port? If so then you could wire in direct to the port and take the 5V/0v from the computer as well, thats the way I have it on the Bridgeport no breakout needed. On the Lathe I have it into my Breakout board and it works fine but thats a PMDX122.
Hood
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rogerbsstt
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« Reply #4 on: December 21, 2008, 07:12:43 PM »

Hood,
Thanks,
I have a second port in the computer so I will try it,

Thanks
rogerbsstt
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Sage
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« Reply #5 on: December 21, 2008, 07:53:19 PM »

Is a pullup resistor required on the parallel port input pins?

Sage
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Hood
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« Reply #6 on: December 22, 2008, 06:12:49 AM »

Is a pullup resistor required on the parallel port input pins?

Sage

Are you meaning if connected direct to the Parallel Port? If yes then I didnt but that may depend on the type of MPG?

Hood
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Sage
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« Reply #7 on: December 22, 2008, 08:32:22 AM »

It seems he has lost his logic levels in the transition through the BOB.
I'm not familiar with the model of BOB quoted above.  Maybe the outputs of the BOB which are connected to the parallel port inputs require a pull up to restore the logic levels. They would be required if the bOB had open collector drivers on the output.
I'm not sure if parallel port inputs have internal pullups to satisfy the requirement.
It wouldn't hurt to try a pullup of 4k7 or so between the parallel port input (along with the BOB output) to +5v to see if the logic levels return.


Sage
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Hood
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« Reply #8 on: December 22, 2008, 08:37:42 AM »

ah got you Smiley
Hood
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rogerbsstt
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« Reply #9 on: December 22, 2008, 03:50:55 PM »

Gentlemen,
thank you all for your comments.
The CNC4PC C10 breakout board has pulldown resistors on all input & outputs according to their documentation.
I will try all the ideas offered in the next few days.I have a second parrallel port on the computor.
Sage, is the pullup resister you suggest a 4.7 kilo ohm value.?
Any further suggetions will be welcomed.

again Thanks
rogerbsstt
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