Tag Archives: mjbots

Improved mjbots labels

For most of mjbots’ existence, all of our products were labeled with a dependable, if lackluster, Brother P-Touch label maker. In line with other packaging improvements, I recently upgraded that labeling setup to bigger, higher resolution, and full color!

This is using an Epson TM-C3500, which I had expected to operate directly from my Linux based test fixtures. However, upon receiving it, discovered that alas only Windows drivers were available. Thankfully, it wasn’t too bad to print from python in a simple way as long as you manually select the media type from the Windows dialogs. Thus I made up a simple Flask app to receive label images over HTTP and print them. That runs on a Windows computer, and the test fixture applications just POST their label images to it.

The qdd100 even has a nifty graphical summary of some of the automated test results graphed on the label.

Since I was hacking on it the bar code URLs are live now too. They show a summary of the test results for each individual unit, although the HTML they produce is pretty minimal even by my standards!

new product day: mj5208 brushless motor

Welcome to the newest mjbots.com product, the mj5208:

This is a high quality 5208 sized 330Kv wound brushless motor with short pigtails intended to connect to moteus controllers. All the moteus devkits as of last week are shipping using this motor instead of the previous “semi-random” motor.

Specifications:

  • Peak torque: 1.7 Nm
  • Mass (with wires): 193g
  • Peak power: 600W
  • Kv: 330
  • Dimensions: 63x25mm

There are two bolt patterns on the output, a 3x M3 17mm diameter one, and a 2x M3 pattern spaced at 12mm. The stator side has a 4x M3 pattern spaced at 25mm radially and a 3x M2.5 spaced at 32mm. The axle protrudes a few mm from the stator, making it easy to adhere the diametric magnets needed for moteus.

New product day: moteus heat spreader

The moteus controller is capable of a lot of instantaneous power. However, to fully make use of that power, you’ll need to keep the mosfets cool on the board. moteus has two mechanisms for that:

  1. A heatsink can be mounted to the bottom side of the PCB between the board and the motor. This is most useful when integrated into a servo motor, and the servo housing can be used as a heatsink.
  2. Mounted to the top of the board, attaching to the MOSFETS directly.

In addition to the MOSFETs, the gate driver chip, the DRV8323 can produce large amounts of heat, especially when the controller is run at a higher voltage, like the 44V that the moteus r4.5 supports.

Getting the heat out of all those irregularly spaced components on the top can be tricky, thus mjbots.com now has the moteus heat spreader:

This precision machined and stylish black anodized aluminum piece fits over the top of the PCB and mounts flush against both the MOSFETs and the DRV8323 to ensure optimal heat dissipation from all components. It can be used as-is, or with an additional heat sink fixed to the flat upper surface.

Don’t hesitate to ask any questions in the mjbots discord!

mjbots repository reorganization

In the spirit of “most of your users are yet to come”, I’ve gone through a moderate re-organization of some of the mjbots github repositories to make them more usable and sensible.

The biggest change is that mjbots/moteus has had a history rewrite and a directory structure re-organization. The current development (and default branch) is now “main”. The biggest changes:

  • Proprietary pdfs have been removed
  • All hardware which isn’t related to the moteus PCB has been removed
  • The firmware source has moved from “moteus/” to “fw/
  • The client side utilities moteus_tool and tview have moved to the “utils/” directory
  • There is now a “lib/” directory which houses client side libraries

Second, mjbots/power_dist is a new public repository that houses the power_dist board firmware and software.

Third, the hardware and software for the quad A1 is now located at mjbots/quad. This repository is rewritten to remove all things that are not quad related, and also to remove proprietary pdfs.

If you have questions about where things are, don’t hesitate to ask in the mjbots discord!

shop.mjbots.com

In my quest to create a more dynamic quadruped, I’ve started accumulating a lot of parts from bulk buys that could be reasonably useful to other hobbyists and experimenters.  To maybe make life easier for everyone, I’ve started up what may be the worlds ugliest online shop where you can buy some of these components.  For now, I have some bearings and custom gears that are useful when building servos for dynamic robots.

Check it out! https://shop.mjbots.com

Unfortunately US shipping only for now, email me or DM on discord to arrange something internationally.

Some samples of what I have online now:

M0.5 100 Tooth Steel Ring Gear

m05_100tooth_internal_right

55mm +0/-0.02 mm outer diameter and 5mm width, only $17 each.

M0.5 20 Tooth Sun Gear

m05_20tooth_sun_front

5mm tooth width, 4mm ID bore, 8mm OD hub, only $6

6708-2RS ABEC-1 Bearing 40x50x6mm

6708-2RS-bearing-right

50mm OD, 40mm ID, 6mm width, only $8

 

 

mjbots discord server

Over the last couple of months, I’ve had an increasing number of people looking for help with self-built moteus controllers which is great!  However, until today there hasn’t been a great way to get help.  Blog comments fall off the front page quickly, and there is no real other mechanism.

Thus, I’ve created a discord server:

There you can chat about the moteus controller, servo, or the quada0 and get feedback and help in closer to real time.  Thanks for collaborating!