u/AidanofVT

Hello,
I am in the final stretch of a mechatronics Masters degree program, and my thesis-equivalent project is to build a robot cell around a Mitsubishi RV-6S 6-axis robot.

The trouble is that the CR2B-547 robot controller refuses to communicate with the outside world in any way. I'll make a separate thread about the difficulty my partner and I have had connecting to a Windows PC, but the more urgent issue is that we cannot get digital IO to work. We need this in order for our PLC to control the robot!

This table, found on page 3-62 of the robot specifications and page 9-457 of the detailed controller manual, is the basis for our work:

https://preview.redd.it/xlszo2o9br5h1.png?width=1382&format=png&auto=webp&s=74b0ce5fd32932b32ffc4235afe899958571307e

It’s possible that we are misinterpreting its relevance, but the “CN100” label matches what we see printed by the port we’ve been using.

We are only trying outputs, because they can be tested with a multimeter, whereas an input would require some sort of robot motion logic to indicate a result. We assume that any approach which works for outputs will also put us on the right track for inputs.

We use a 24VDC power supply to put positive voltage on Pin #3, and 0V on Pin #2. We then measure the voltage of pins 4-7.

We have tried measuring both relative to ground and relative to +24V. Measuring relative to 0 tends to be more “noisy”, with the measured voltage oscillating between 0V and single-digit positive volts faster than the multimeter can register. Measured relative to +24V, the signal is a relatively steady 1 to 2 volts on all pins.

We have tried using both pull-up and pull-down resistors (5,000 Ohms in both cases). These function as expected, but do not reveal any signals from the controller. Curiously, when a pull-up resistor is used, the signal pin shows minimal voltage relative to both 0V and +24V.

Seeing that pins 4-7 have alternate functions, we have also tried this same operation on pins 27 through 32. The only difference is that measuring relative to ground shows 0V, rather than noise.

Pins 4-7 never seem to function according to their alternate functions: they never indicate error, servo, or running status.

Our test programs rely on M_OUT. Here’s an example:

MOUTNOW = 1 
WHILE(1) 
FOR M1 = 29 TO 31 
M_OUT (M1) = MOUTNOW 
NEXT M1 
MOUTNOW = 1-MOUTNOW 
DLY 2 
WEND 

The teach pendant’s output-monitoring function allows us to confirm that the programs are working as intended.

We’ve tried with and without servos engaged.

We believe that the argument to M_OUT is supposed to refer to physical pin numbers, but we have also tried it with the output numbers. For instance: we have tried “32” and “7” for the same pin.

So, after more than a week of troubleshooting, the only remaining idea I have is that some piece of hardware has silently failed. Maybe one of the non-replaceable, location-unspecified fuses has blown. I'm really hoping that someone here can give my partner and I a clue towards a different explanation; our capstone project kindof depends on it.

Thanks in advance.