Encoder wiring - Mesa 7i33

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12 Mar 2011 21:46 #7759 by Fordperf393W
I am trying to hook up 4 encoders to a mesa 7i33, after researching I am more confused than when I started. Hopefully I can get atleast some guidance.

The encoder employs a 5 wire TTL signal:
Signal wires as follows: OV, A, +5V, B, Z

I have read many web sites and posts on forums mentioning using signal wires ENCA0, /ENCA0; ENCA1, /ENCA1; ENCA2, /ENCA2; ENCA3, /ENCA3, from the 7i33, but no idication to which wires they connect to on the encoders, with that, this only covers 2 of the 5 wires on each of the encoders.

Any help would be greatly appreciated.

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12 Mar 2011 22:21 #7762 by radekB
Set the Wx svitch for the TTL signal input on a 7i33 board !!! Read the manual page for 7i33 board.

RADEK
Attachments:

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13 Mar 2011 11:03 #7778 by andypugh
Fordperf393W wrote:

The encoder employs a 5 wire TTL signal:
Signal wires as follows: OV, A, +5V, B, Z

That is three signals and power. 0V is GND (or Earth). The quadrature signals are A and B and the Index (one pulse per rev) is called Z.

I have read many web sites and posts on forums mentioning using signal wires ENCA0, /ENCA0; ENCA1, /ENCA1; ENCA2, /ENCA2; ENCA3, /ENCA3, from the 7i33

That is for a "differential" wiring scheme, where each phase has two wires (so A and /A, B and /B, Z and /Z) You are using TTL so need to ignore the /A /B and /Z pins. (and probably set a jumper on the board). The numbers on the signal names above refer to the encoder number.
If you look at the picture that Radek posted, you need to follow the scheme in the bottom left quarter, and ignore the rest.

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19 Mar 2011 00:10 #7925 by Fordperf393W
Well, I got everything hooked up per the provided diagrams. I used pin 49 for +5 to the 7i33 and the encoders, is this ok or should I tap off the computers PSU?

I launched emc using the provided 5i20 sample file, but I get no readout. are there any other drivers I need?

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19 Mar 2011 00:34 #7927 by andypugh
Fordperf393W wrote:

I launched emc using the provided 5i20 sample file, but I get no readout. are there any other drivers I need?


What do you mean by "Readout" and which firmware is the config loading? (dmesg will tell you, a bit above the pin listing)

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19 Mar 2011 02:32 #7931 by PCW
Replied by PCW on topic Re:Encoder wiring - Mesa 7i33
Using the cable power is ok up to around 400 mA (about 75 mA per encoder plus 100 mA for the 7I33 card)
if the encoder draw more power you may want to supply 5V to the 7I33. The easiest way with a 5I20 is to take 5V power from the terminal block on the 5I20, this can supply up to 2.5 A or so and is protected by a PTC so you wont fry any wiring or PCI sockets if you short out the 5V.

If you do not get any encoder counts, I would check that:

1. The 7I33 has power (three LEDs on)
2. With the original HM2-servo config, you have the 7I33 connected to P2 (I/0 0..23)
3. That you have your encoders properly connected ( the voltage measured on the A or B lines should change alternately from high (3-5V) to low (close to 0V) if you move the motor shaft
4. You have the 7I33 jumpered for TTL mode

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22 Mar 2011 22:20 #8011 by Fordperf393W
Possibly I have been over looking one thing, I have the GND pin connected to GND on the 7i33, but the pinout of the encoder also shows a 0V pin which is connected to the sheilding of the cable running to the encoder. Should I be grounding this pin also? and to where?

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22 Mar 2011 23:12 #8012 by PCW
Replied by PCW on topic Re:Encoder wiring - Mesa 7i33
Normally I would connect the shield only to one end of the cable (better at the 7I33 end) But the shield should not affect basic encoder operation. Can you measure 5V between the encoder power and ground pins at the encoder end of the cable? If the encoder has 5V (a 5V and a GND) then the encoder should be outputting signals you can see with a voltmeter (or even a LED and ~300 Ohm resistor)

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23 Mar 2011 02:05 #8016 by Fordperf393W
Well, I would just like to thank everyone that helped me out. Finally ended up taking apart the DB9 connector supplied on the encoder wiring to find out the mfg swapped the GND and 0V from what their pinout showed. Works like a champ.

I do however have one last question, the m5i20 sample config states the ability to read 4 encoders, it is only pre-loaded for 3. While i'm not well versed with linux, I tracked down the config files but they only open up as "read only" in gedit.

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23 Mar 2011 11:11 #8026 by BigJohnT
You should have created a config (usually by running EMC) and that would create a directory called emc in your home directory. In there you will have to sub directories configs and nc_files and your config will be in the configs directory. If you have drilled down from root to find a config your in the wrong place.

To change the number of encoders you change this line in your ini file
loadrt hm2_pci config="firmware=hm2/5i20/SVST8_4.BIT num_encoders=3 num_pwmgens=3 num_stepgens=1"

www.linuxcnc.org/docview/html/drivers_hostmot2.html

John

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