Tag Archives: power_dist

New product Monday: mjbots power dist r3.1

I’ve displayed versions of this numerous times in the past (May 2019, Feb 2020, March 2020), but now I’m proud to announce that I have a productized version of the power dist and precharge board available in the mjbots store for $79.

This board has convenient connectorization for powering sub-components of your robot, and also provides a smooth pre-charge sequence so that you can safely connect a large battery to high capacitance loads. I made a short video to show it off.

New Mech Warfare turret

Another of the tasks I’ve set for myself with regards to future Mech Warfare competitions is redesigning the turret.  The previous turret I built had some novel technical features, such as active inertial gimbal stabilization and automatic optical target tracking, however it had some problems too.  The biggest one for my purposes now, was that it still used the old RS485 based protocol and not the new CAN-FD based one.  Second, the turret had some dynamic stability and rigidity issues.  The magazine consisted of an aluminum tube sticking out of the top which made the entire thing very top heavy.  The 3d printed fork is the same I one I had made at Shapeways 5 years ago.  It is amazingly flexible in the lateral direction, which results in a lot of undesired oscillation if the base platform isn’t perfectly stable.  I’ve learned a lot about 3d printing and mechanical design in the meantime (but of course still have a seemingly infinite amount more to learn!) and think I can do better.  Finally, cable management between the top and bottom was always challenging.  You want to have a large range of motion, but keeping power and data flowing between the two rotating sections was never easy.

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The legacy turret

My concept with this redesign is twofold, first make the turret be basically an entirely separate robot with no wires connecting it to the main robot and second, try to use as many of the components from the quad A1 as I could to demonstrate their, well, flexibility.  Thus, this turret will have a separate battery, power distribution board, raspberry pi, pi3 hat, and a moteus controller for each axis of motion.  These are certainly overkill, but hey, the quad A1 can carry a lot of weight.

The unique bits will be a standalone FPV camera, another camera attached to the raspberry PI for target tracking, a targeting laser, and the AEG mechanism, including a new board to manage the firing and loading functions.

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A static rendering

And here’s a quick spin around video:

More to come…

Updated quad pi3 hat

I made a number of tweaks to the quad A1’s raspberry pi hat to get it ready for production, resulting in r4.1 of the board:

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None of the changes were particularly big, but each has some value:

  • The correct switch mode regulator is installed.
  • The auxiliary CAN transceiver was switched to one that supports a larger common mode voltage.  This will allow it to be connected to the power distribution board without smoking.
  • Each of the STM32s now has some GPIO pins connected directly to GPIOs on the raspberry PI primarily to be used for interrupts.
  • Pin headers expose a few gpio pins from each STM32 for interfacing with random external things.
  • The NRF radio module changed orientation and has improved power filtering.
  • I added a microphone to the auxiliary STM32.  The goal is to eventually be able to use that to synchronize external video with onboard data collected during operation more easily.

I’ll bring this up in a future post!

Power distribution board r3

While I was able to make the r2 power distribution board work, it did require quite a bit more than my usual number of blue wires and careful trace cutting.

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Thus I spun a new revision r3, basically just to fix all the blue wires so that I could have some spares without having to worry about the robustness of my hot glue.  While I was at it, I updated the logo:

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As seems to be the way of things, a few days after I sent this board off to be manufactured, I realized that the CAN port needed to actually be isolated, since when the switches are off, the ground is disconnected from the rest of the system.  Sigh.  Guess that will wait for r4.

Here is r3 all wired up into the chassis:

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