Mesa 5i20 - 7i37TA - 7i48

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08 Apr 2012 20:54 #19031 by Will Gilmore
Good to know. I was wondering what I was going to do when I wanted to add an MPG. Thanks!

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08 Apr 2012 21:00 #19033 by cmorley
Ironically the checkboxes are not available with the encoders .... for servo encoders one negates the scale factor.
For MPG I guess everyone just switched the wires... or hand edited the HAL file to negate the scale...

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09 Apr 2012 01:47 #19036 by Will Gilmore
Funny you should mention encoders. Now that I have the i/o working I checked to see if the encoders were working. Y is working perfectly. X and Z show some movement (thous or tenths) when I manually turn the screws. I've checked that the encoders have +5VDC where they should.

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09 Apr 2012 02:06 #19037 by PCW
Replied by PCW on topic Re:Mesa 5i20 - 7i37TA - 7i48
For debugging encoders, first thing to look at is the rawcounts pin (with halmeter)
if it only toggles back and forth one count, this indicates that one of the A/B signals
is not getting to the counter.

If rawcount counts up and down, but the DRO is wrong, then you likely have a scaling problem

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09 Apr 2012 18:37 #19054 by Will Gilmore
x and z rawcounts only toggle back and forth one count as you describe. bad encoders or wiring issue? anyway i can check at the encoder? i dont have a scope.

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09 Apr 2012 18:48 #19056 by PCW
Replied by PCW on topic Re:Mesa 5i20 - 7i37TA - 7i48
Are the encoders single ended or differential?
that is, is there a single A,B and perhaps Z wire or are there a Pair for each? (A,/A B, /B and Z, /Z)

The encoder signals can be checked with a voltmeter or perhaps more easlily with a LED and a resistor

For single ended signals the LED anode should connect to 5V through a say 300 Ohm resistor and the cathode to the encoder signal

For differential encoders the LED+resistor should be connected between the A and /A or B and /B signals

Both the A and B signals should toggle when the shaft is turned slowly

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09 Apr 2012 21:26 #19063 by Will Gilmore
I measured voltage from A+ to A- and B+ to B- at the encoder connector on the X and Z encoders. Unfortunately the Y encoder does not have a connector near the encoder. On both encoders the A readings were between 0V and .5V. The B readings on both encoders were between 3.2V and 3.8V. As I turned the screws the readings move around in those ranges. I tried the LED as well (before trying the multimeter). As expected A wouldnt light the LED and B lit it dimly.

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09 Apr 2012 22:15 #19068 by PCW
Replied by PCW on topic Re:Mesa 5i20 - 7i37TA - 7i48
The A pair and the B pair should behave identically , that is
all pins should have roughly TTL level swings
(with a 0-.4V low and a 2.4 to 5V high)
depending on shaft position
if the A and B pairs behave differently I would check your wiring

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10 Apr 2012 15:22 #19100 by Will Gilmore
I disconnected the z encoder from the main wiring harness to make sure other wiring wasn't affecting the tests. I jumpered +5VDC and GND across to power the encoder. I tested from GND to the four pins at the encoder connector as I turned the screw slowly:
A+: 1.77V, .08V
A-: .07V
B+: 1.77V, .08V
B-: .09V

I also tested from A+ to A- (1.7V,.012V) and B+ to B- (1.69V, .006V)

Do I need a new encoder?

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10 Apr 2012 17:47 #19106 by PCW
Replied by PCW on topic Re:Mesa 5i20 - 7i37TA - 7i48
If this is with the bare encoders (not connected to anything else)
I would say they are either bad or you have the pinout wrong

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