Next large robot



  • your work is simply amazing.

    Thank you for the pictures.

  • I ended up needing to remove the plate over the battery compartment so I decided as long as that was off, I would go ahead and re-route the motor power wires from going up the middle of the deck to bring them up along the sides closer to their connection points. That will require drilling 6, 1” holes in the aluminum so the mill will be used for this process.
    I did a lot of tracing out the wiring and still haven’t found the electrical fault. Its been more difficult than anticipated as there have been many changes and additions to the wiring so wires are heading every which way. Plus I found one connector that isn’t connecting securely and needs replacement. Based on this I decided to re-wire the 12v motor power distribution. I’m laying out the components and putting in dedicated +/- 12v busses and additional wiring distribution points for future additions. Got a new schematic drawn up, got some better wires to use (old wires were very stiff and hard to manipulate). I need a better mounting board for the components so have to figure how to mount that also.
    Having a much smaller battery gives me additional space so there are several options on how to setup the wiring, just need to take my time and get it right.
  • Still no idea on what caused the battery voltage to drop. I’ve examined each component in the power system with no indication where the problem came from.

    So I spent some time Drawing up new electrical schematics with all the electrical changes that have been made. This gave me something to think about what on how to install the electrical system. I found some nice plastic backing material that is fairly rigid and lasers nicely.

    I made up a new electrical panel Design and after a few experiments, was able to cut out the board. Unfortunately the first board caught on fire and I didn’t notice until a whole corner of the board had melted. 2nd board came out fine, here it is right after the laser finished cutting.

    I added a a lot of labels to help identify wires in future troubleshooting sessions. I used a white screen printers ink to fill in the ‘cut out’ lettering and device outlines.

    Here is the board mounted across 2 sides of the hexapod battery level. With the smaller battery I now have lots of room for this style of layout. I am getting ready to start running wires now.

    Here is a different viewpoint of the battery level. The area on the right side is the fuse panel for motor power distribution. On the opposite side is the fuse panel for computer power distribution.

    Lots of wires to tie in and make everything pretty. I still have a couple of parts out on order so I won’t be able to finish it up tonight. Should get most of the basic wiring done so I can test everything.
  • Looking very professional, Bob!
  • Fun day wiring up and testing the new power panel. Here it is with the new wiring. Still need to put in some zip ties to tidy it up.
    Here is the back side of the panel. Lots of cleanup still needed here. These are all small wires from the Plug-in sockets.
    Tested the power system as each section was wired together to make sure I didn’t accidentally create any wiring errors. I have good power output to the motors and computers now. I had to put some epoxy on the sockets on the right side, the plastic panel is fairly thick and the laser makes the sides of the cutout slick so the sockets want to push them out when I plug into them. That’s what stopped tonight’s work as the epoxy needs to cure.
    Next step is machining some new access holes in the aluminum plate that is the top of the battery level. This is to provide better routing of the power cables up to the motor controllers and computers through the deck. Right now the power cables pass up through the middle of the plate and then fan out to the motor controllers. This just makes a mess/maze of wires on the motor level. The new holes will be along the outer edges of the plate making the wiring less messy.
    I finally realized that there were 2 sets of fuses in series going to the motor controllers. I believe I put some in-line fuses in originally before I got the dedicated fuse panel that I’m using for power distribution. Removing those fuses will help with the wiring simplification process.
  • During the wiring process I finally got the Lascar voltmeter panel re-programmed for lithium batteries and installed. That’s when I noticed that the battery was showing 14.24 volts with no load but as soon as I turned on the main key switch the voltage dropped to 13.9v. A considerable drop since it only powers up a 12v LED at that point. Turning on either the motor or computer supply with nothing connected except the relay and indicator LED on the switch dropped the voltage to 12.7v. Clearly there was a serious problem. After extensive checking I couldn’t find any wiring error that could cause the symptoms I was seeing so I started to suspect the battery itself. I removed the shrink wrap and made measurements directly from the battery terminals, upstream of the BMS. As I suspected, the actual battery voltage didn’t change as I turned the switches on and off. Pretty clear indication that I got a bad BMS board. Visual inspection didn’t show anything obviously wrong, I couldn’t feel any hot spots (maybe it’s time to get a thermal imager) either. I contacted the vendor and they agreed with my assessment and will send a new board as soon as they get new ones in (shipping delays due to COVID-19).
    I’m using the time to clean up some other wiring and fix a few things I always planned on getting around too but never found the time. Should have the power system re-wiring done in the next couple of days and then start re-assembly. I want to permanently mount the master computer and figure out a better mount for the 6 RoboPi computers. The RoboPi computers have only 2 mounting holes that are diagonal from each other so the boards are wobbly as I plug and unplug connections. This has resulted in stripping the tapped holes the nylon screws connect to, and the boards fall down. There has to be a better method of securing the boards. I think I could machine a plastic ‘box’ that holds the board by the edges and then attach the box to the wall.
    If I haven’t received the replacement BMS by the time I finish all that, I can temporarily bypass the BMS and run the robot directly off the battery. I don’t want to start drawing large loads on the battery without a functioning BMS to avoid damage to the battery.
  • Worked more on re-routing the computer and motor power wiring. Came to a standstill on that when I needed to crimp some Molex power connectors and realized the last time I crimped I borrowed a crimper from work. Since I’m retired that avenue isn’t available so I had to order a crimper to arrive next week. In the mean time I’m working on other robot related ‘fixes’ that need attention.
    First, came up with a better way to mount the RoboPi boards, a long standing problem.
    Using the laser cutter I cut a plastic frame the fits around the board. At the top and bottom are retaining strips of plastic that keep the board in-place.
    Here is what it looks like installed. The plastic frames are glued to the plastic outer skin panels.
    Next task was removing the master computer to drill and mount a centrally located eye bolt for attaching the rope safety harness while testing various leg routines. This requires the master computer to be moved so I mounted it next to the eye bolt and secured to the computer level deck. Not sure I like that location yet but it can be easily moved later if needed.
    Cleanup of the power wiring meant moving all the main wiring runs to the battery level and then up to the individual legs. With the lithium battery requiring much less space than the gel cell, there was room to move the 12v to 5v DC-DC Converter down to the battery level. Way in the back of the photo is the backside of the new power board. I moved the shunt back here as the spot on the front of the board had it interfering with the battery level plastic covers.
    Lastly, here is a view of the interior of the motor level, much cleaner less cluttered with wires running everywhere. Seems like a waste of space, at least until the coxa motors slide in there.
    Going to be mostly on hold until the crimper arrives. Then I can start re-assembling the legs and get back to programming again.
  • DiverBobDiverBob Posts: 783
    edited 2020-06-02 - 04:28:01
    Got the new crimper a few days earlier than expected so was able to put together the new power connectors to the motor controllers. Since everything looks nice a pretty now I put together a video walkthrough of the robot base in its present form. I also video’s putting all the legs back on but that takes 30 minutes and I could only change the speed by 2x with my software so I left that out.
  • just WOW.

    Love your attention to details.

    go Bob go...

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