Scorbot ER4U Homing Issues

[ElectroNick]

Before you can use a Scorbot robot, it has to be homed every time you turn the controller on. Many old robots have issues homing due to misaligned cam switches, broken encoders and such.

Please post a better description of the robot's behavior during the homing procedure and we'll try to identify the issue.

If you haven't seen the Eshed Robotec's document describing the Scorbot homing procedure , definitely check it out. It outlines the mechanical part of the procedure and setting up the cam switches.

 

[Dave]

I moved on the the next robot today.  This robot was moving very sluggishly when attempting to home and eventually crashed into itself.  I then plugged the cable into the other control box to home the robot.  This worked, so I am looking at the control box.  The robots are well out of warranty so I am going to open the bad box tomorrow.  Do you have any suggestions on what to look for.  Do you have any kind of technical forms to diagnose the electronics inside the control box.  I am first going to look at the power supply due to the sluggishness.  But how do I know what voltages and amps. the components should be providing?  Any suggestions?
Dave

[ElectroNick]

Hi Dave, so the same robot plugged into a different controller homed fine? Just making sure.

Also, do all axis show the same sluggishness?

The control box (Scorpower) is more like a power supply, really. That and the driver for the motors. All the controlling is happening inside the software on the PC. But as far as what voltages to expect inside the box, there should be +5V and +12V in there.

I actually had to repair my Scorpower USB box myself before I could use it. From my own experience and hearing from other Scorbot enthusiasts, the large electrolytic capacitors in the power supply very often go bad. Mine had the cap on the input side on the +5V voltage regulator shortened. I had to replace the cap. Another possibility is the voltage regulator itself could have given out.  These are pretty archaic linear power supplies and they use the classic 7805 for 5V and 7812 for 12V regulators, except they are using rather hard to find 3A versions. Most of what's sold out there is 1A, so be careful if you're looking for places to buy one.

I am thinking there's nothing wrong with the +5V branch since otherwise neither USB nor lights would work on the box, it'll just look like it's completely dead. On the other hand, if 12V is not quite 12V, it may explain the sluggishness. Maybe there's yet another shortened or dried out capacitor, this time on the output side of the 7812 regulator?

Unfortunately, the PCB is a real pain to remove - it's bolted down to everything really good. But once you get it out, the repair (if it is indeed power-related ) should be relatively easy. Pop the old capacitor, put the new one in. If it did not fix the issue, replace the 7812. That should do the trick.

Of course, there could also be something entirely different that I can't see. Let's just hope it's not the transformer that feeds that 12V regulator. A replacement for that puppy would be next to impossible to find and no one in their right mind would rewind a transformer these days.

Anyhow, I hope it's something less dramatic. My guess is that a dried out or shortened electrolytic capacitor is the culprit once again.

Good luck!

[ElectroNick]

Dave, if you are still struggling with this homing  issue, I just verified on one of my robots the issue of reading encoders while homing the robot that has come up before in your earlier post.

It is possible to see the encode values during homing but you need to enable the "Encoder Count"  dialog box before starting the homing procedure. The software is not responsive during homing, so you can't enable the "encoder" box when you're already going through it. The workflow of the Scorbase software kinda pushes you into doing the homing the first thing after you start it. But if you cancel out of the dialog boxes the software throws at you instead of confirming the defaults, you can get to View -> Dialog Boxes - > Encoder Counts   to enable that box and then turn the power to the controller on and start homing the robot.

This way you can see if there's a problem with any particular encoder that prevents certain axis from homing.