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HermannSW
Posts: 4010
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

1ms shutter speed 90fps slowmo dark – not with NoIR camera!

Thu Jul 13, 2017 5:29 pm

I always had a Raspberry camera on top of my Motor Test Station in order to take 90fps (640x480) slowmo videos of my high speed robots in MTS. Since recently I did take a 2nd video from an Android phone camera from top as well, for real time video, and more importantly, for audio!

Latest addition to this setup is a third Raspberry NoIR camera, looking at the sceen horizontally through a peephole (click image(s) for details):
Image

The last run I did showed "only" 14m/s or 50.4km/h speed (record sofar is 68km/h, with only 25% of ESC control speed for outrunner motors). Here are the three videos:
https://www.youtube.com/watch?v=BxyT9ul ... e=youtu.be (69) Android phone camera
https://www.youtube.com/watch?v=gJfhBHa ... e=youtu.be (69a) Raspberry camera
https://www.youtube.com/watch?v=3Ta642G ... e=youtu.be (69b) Raspberry NoIR camera

So lets start with a single frame from a 90fps slowmo video with default shutter settings of raspivid, which I assume is 11.1ms because consecutive frame pictures start where previous frame ended, and stop where next frame starts. This video was also taken at a >50km/h speed:
Image

As you can see this frame is really smeared. I always accepted that, because it did no hurt in counting the avarage number of frames per round of the robot (with the 1.28m wheel radius that easily allows to compute robot speed).

Today I looked up raspivid's "--shutter" option, and I really like it!

So this is frame from (69a) video, taken with "--shutter 1000":
Image

A (nearly) perfect frame, nearly no smearing, and you can even read the value of digital voltmeter on the spinning robot! (click on the image for that to see in original 640x480 size) Only drawback is that the frame looks a bit dark, and I know that the reason is that in 1ms not enough light can be accumulated. Again, for measuring average frame rate that is perfect.

Finally here is a "--shutter 1000" frame of the Raspberry NoIR camera looking through peephole, also at robot speed of 18m/s:
Image

No darkness! The reason is simple, and can be seen by the 3W Infrared LED mirroring in safety glass. The wheel looks a bit strange, but hey, it passes with 14m/s and 1ms is even a long time for that speed ;-)
(robot moves 1.4cm in 1ms)

Summay:
I was and and will be a heavy "raspivid" user, and learned today on "--shutter" and am really impressed!

Hermann.

P.S:
More details on the latest Motor Test Station changes and runs in this posting:
https://forum.arduino.cc/index.php?topi ... msg3338067
Image
https://stamm-wilbrandt.de/2wheel_balancing_robot
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://github.com/Hermann-SW/raspiraw
https://stamm-wilbrandt.de/en/Raspberry_camera.html

User avatar
HermannSW
Posts: 4010
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: 1ms shutter speed 90fps slowmo dark – not with NoIR came

Sat Jul 22, 2017 1:48 pm

Adding a (cheap) Ikea 1000lm lamp to existing halogen desk lamp
(click on images for details)
Image

greatly enhances brightness of 640x480 @90fps with 1ms shutter time taken frames, from
Image

to this!
Image

Wheels turned with >25rps (or 1500rpm) ...

Hermann.
https://stamm-wilbrandt.de/2wheel_balancing_robot
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://github.com/Hermann-SW/raspiraw
https://stamm-wilbrandt.de/en/Raspberry_camera.html

User avatar
HermannSW
Posts: 4010
Joined: Fri Jul 22, 2016 9:09 pm
Location: Eberbach, Germany
Contact: Website Twitter YouTube

Re: 1ms shutter speed 90fps slowmo dark – not with NoIR came

Sat Jul 22, 2017 2:40 pm

I really like 90fps video taking for measuring stuff.

Here is the 1st not that bright slowmo video taken for 1st motor+wheel pair:
https://www.youtube.com/watch?v=Q2sYRAi ... e=youtu.be

No noticable excentricity! Wheel turns clockwise, speed is 2 rounds per 7 frames (follow the black marker). This gives 2*(90/7)=25.7rps or 1542rpm (12V 1500rpm motor, 3S LiPo with 12.6V). Wheel diameter is 65mm, and motor has high torque, theoretically that means 5.25m/s or 18.9km/h. Not high speed, but above my 5m/s linear max speed requirement.

Here is the 2nd bright slowmo video taken for 2nd motor+wheel pair:
https://www.youtube.com/watch?v=wuqHwRd ... e=youtu.be

No noticable excentricity! Wheel turns counterclockwise, speed is 5 rounds per 17 frames (follow the black marker). This gives 5*(90/17)=26.4rps or 1588rpm (12V 1500rpm motor, 3S LiPo with 12.6V). Wheel diameter is 65mm, and motor has high torque, theoretically that means 5.4m/s or 19.4km/h. Not high speed, but above my 5m/s linear max speed requirement (for line following robot).

Hermann.
https://stamm-wilbrandt.de/2wheel_balancing_robot
https://stamm-wilbrandt.de/en#raspcatbot
https://github.com/Hermann-SW/Raspberry_v1_camera_global_external_shutter
https://github.com/Hermann-SW/raspiraw
https://stamm-wilbrandt.de/en/Raspberry_camera.html

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