Motor Test Station (MTS)

OK, I rebuilt the Motor Test Station.

First I turned the base board, there were too many holes. And to avoid the base board from moving as in the end of last video, I used nails in the corners to fixate the base board on the desk (click on the photos to see more details): |500x375

Here you can see the replacement for the safety glas surrounding. I hope that the4 fixing brackets will avoid bullet plus motor to go throug the wall from now on: |500x375

This is top view from Raspberry camera, which normally takes the 90fps videos: |500x375

Finally I replaced the wooden motor mountings with plastic. I hope that it has same behavior as wood wrt vibrations, but is more stable than wood: |500x375

Test runs would be too loud now at night here, will do tomorrow,

Hermann.

I did a further modification to MTS, added a peephole for third Raspberry NoIR camera to take horizontal video for bump analysis. More details in forum posting 1ms shutter speed 90fps slowmo dark – not with NoIR camera! |500x375

I started like most others with aluminum outrunner motor mounts, but with what I do I always break these: |500x375

Next step was to use self made mounts of wood, but they splittered: |375x500

Next was to use self made motor mounts from plastic, a really bad idea. At least the plastic I used was too brittle and quickly just broke: |500x375

Next I tried to go back to my roots. Normally I do (nearly) everything with superglue, and so I did here as well, I superglued A2212 outrunner motor to beaverboard ... |500x375

... and then superglued beaverboard to robot wooden beam: |500x375

I had to cut a center hole into beaverboard because of the outrunner motor moving parts. In order to do minimal stress to beaverboard, I created the hole with soldering iron: |500x375

This is the final robot motor wheel connection: |500x375

I have already done many runs with the new superglued outrunner motors in motor test station, now its really reliably, and the robot ends a run as he did start, with all wheels and motors attached ;-) My explanation for this is that the (metal) base area of A2212, even without the round center moving part is so big, that supergluing that whole area to beaverboard is much better than 4 screws:

Last, but not least, some 90fps slowmo video action ;-) Click the animated .gifs to see in 640x480 size.

From peephole 90fps slowmo video: Robot starts with spinning wheels, bumpy, but goes smooth later. Animation is slowed down by factor of 10: |500x375

And a reminder to myself: "Don't forget safety glas cover on Motor Test Station!" Wheel lost at 52km/h hits wall, then goes up out of MTS, near miss of top camera!! (1 frame of 90fps slowmo video per second, slowdown factor 90) |500x375

Hermann.

Two days ago I did a further run, but that run was different, robot did go wild. The Arduino sketch should run the robot for 10 seconds and then stop, letting robot roll out to stand still. For yet unknown reason the robot repowered again and again, starting the 10s cycle without stop. Speed was far to high to stop robot by hand. Had to wait for 5 minutes until robot stood still so that I could cut power. In the end the digital voltmeter on robot showed less than 9V under motor load. It shows 12.1V without load, so the 3S 11.1V LiPo was not empty. During the whole run the robot smelled like some cables roasted, after the end I was able to locate the smell on mini breadboard where all the cables are connected: https://www.youtube.com/watch?v=bvvGuT4TS3g

Yesterday I unscrambled mini breadboard cables and uncovered a reason for last run bad smell, the blue, 2nd ESC GND cable got burned, too many amps: |500x375

Further unscranbling of mini breadboard cables revealed, that mini breadboard does not like too many amps either ;-) [left and right column, bottom 3 connections] |500x375

Time for recabling and not using breadboard nor breadboard cables for links that get several amps, and to use a real power on/off switch,

Hermann.

P.S: At fastest run the robot did 18.77/1.28=14.66rps or 880rpm. Vertically mounted Arduino Uno had no problems to operate at 14.66rps, and I suspect the not perfectly plugged in AWG power cable to be the reason for robot going wild and not the Uno.

I did all the MTS rps/rpm determination with 90fps videos because I did not know that Raspberry cameras can be talked into doing much higher framerate videos (up to 750fps with 6$ v1 China clone 5MP camera, up to 1007fps with 30$ v2 8MP camera)!

With Motor Test Station rpm always was in 3-digit range and 90fps was more than enough. Recently I successfully determined the rpm of RC airplane with 1007fps video as 20140rpm. Just wanted to post here in case others need/want to visually determine fast rotational speed. This is 640x75 video recorded at 1007fps, played at 1fps: https://www.raspberrypi.org/forums/viewtopic.php?f=43&t=190407&p=1319617#p1319617 |500x58

Very high framerate means low shutter time, so very bright light is needed, I used 5000lm led here: |500x375