mBot 2 not always recognising colours

#1

Hi all, I’m testing soms mBot’s for in my classroom. I’m trying to add code to colour recognition and I’m using the default sheet that I got in the box.

I’m having troubles with the recognition of the colours, it just doesn’t always see the green/yellow/blue/red as it should. Sometimes it does, sometimes it doesn’t.

I really would like some more info and tips about the RGB sensor. What does the RGB calibration block in mBlock mean, for example? And other specific RGB sensor blocks?

I would really like some example code for RGB and/or a more in depth manual. Where can I find such information?

#2

The lighting conditions and the distance of the sensor from the detected object change the reading greatly, sadly. :confused: You can try to mount the sensor a little lower using spacers, and it sometimes helps. Not much you can do, though, as it is a hardware issue.

#3

Thanks for your reply!

Do you mean even lower than the default position? I will try it for sure.

But I find it fascinating that it doesn’t even recognise its own track. Tracking the black line is fine, but colours are problematic even in the same lighting conditions.

And also that there are certain RGB codeblocks that I don’t really understand, but I can’t find an explanation or tutorial also :frowning:

#4

Which ones @BobB? I can tell you what they do!
Good luck!

#5

Very kind of you! :slight_smile:

  • What is color detection mode standard / enhanced?
  • How does the calibration block work?
  • What does the deviation of the colors do?

Can those blocks improve the recognition of the default colors? If not, what could I do?

I just want the sensor to work consistently, otherwise I can’t teach this subject to my students.

#6

Check out the docs here:

https://education.makeblock.com/help/mbuild-quad-rgb-sensor/

and here:

https://education.makeblock.com/help/mblock-block-based-device-cyberpi-extension-quad-rgb-sensor/

What does the color detection mode mean?
The algorithm of the quad RGB sensor is performed based on the hue, saturation, value (HSV) color model. The standard mode refers to the threshold used in earlier firmware versions, and the color enhanced mode is added to the latest firmware, in which the threshold is adapted to application scenarios based on the HSV model. You can select a color detection mode as required.

See more details
image

Why do I need to perform calibration on the quad RGB sensor?
The performance of the quad RGB sensor may be significantly affected by the ambient light, map, color card, or the distance between sensors and the object to be detected. Therefore, performing calibration on the quad RGB sensor in the environment and conditions where it is to be used can improve the detection accuracy.

Calibration preparation

  • Update the firmware to version 011, and update the Quad RGB Sensor extension to the latest version.
  • Assembled mBot2, or CyberPi + mBot2 Shield + quad RGB sensor
  • White paper of A6 or larger, or the white area on the mBot2 line-following map
  • Find a place with common room light instead of intense light
    Calibration steps
    (1) Connect the quad RGB sensor to the mBuild port on mBot2 Shield or CyberPi by using an mBuild cable.
    (2) Connect CyberPi to your computer by using a USB cable.
    (3) Open mBlock 5 and connect CyberPi to mBlock 5.
    (4) Add the Quad RBG Sensor extension.
    (5) Write the following program and upload it to CyberPi. Alternatively, you can write a program in live mode.
    image
    The calibration process is short. Place the quad RGB sensor (12 mm to 13 mm recommended) over the white paper before you start the calibration program.
    image
    image.png1036x792 47.1 KB

    During the calibration, the fill lights are lit up in other colors and then reset to the pre-defined color, which looks like blinking. When the calibration is complete, it says “Calibration completed” on the screen of CyberPi. You can execute the program to perform calibration on the quad RGB sensor again.

Assuming you mean tolerance:
image
Define a color and its tolerance
You can define a color with the following RGB ranges:
R: 0–255
G: 0–255
B: 0–255
Tolerance
For example, set the block as follows:
image
Initial RGB values

255
40
40

If tolerance is set to 10, then:
Upper limit of RGB values

255
50
50

Lower limit of RGB values

245
30
30

You can set the tolerance based on the ambient light and object color differences.
image

I hope the docs help you @BobB. They are very thorough. :slight_smile:

Best Regards,
Best_codes

#7

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