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>#### Activity duration:
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> 4+7+7+3 hours
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> 4+8+6+5+4 hours
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>#### Overall goal
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>In this lab session we will try to make two different self-balancing LEGO robots. In order to do this, we use 3 different sensors, which include a light-sensor, a color-sensor and an gyro-sensor. The exercises for this week, are as follows:
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>#### Results
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> We decided to test the light sensor under different settings. First we tested how it reads black and white values at different surfaces (plastic and paper) and under different light settings (dark and bright). As further investigation we tested how the sensor is able to detect dark green and light green. The findings from the light sensor tests are presented in the table below:
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> | Black reading | White reading | Black White Difference | Black White Threshold| Dark Green reading | Light Green Reading | Green Difference| Green Threshold |
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> | -------- | -------- | -------- |--------|-------- |--------|--------|--------|--------|
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> | Bright Room Paper surface | 33 | 55 | 22 | 44 | 39 | 44 | 3 | 41 |
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> | Bright Room Plastic surface | 25| 52 | 27 | 38 | 34 | 32 | 1 | 33 |
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> | Dark Room Paper surface | 28 | 52 |24 | 40 | 34 | 34 | 0 | 34 |
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> | Dark Room Plastic surface | 26 | 47 | 21 | 36 | 24 | 28 |4| 26 |
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> After initial tests with the LEGO model suggested by Hurbain, we made a small change to the wheel assembly. We noticed that the motor power was different for each motor which made the robot turn slightly. We solved this by making a fixed axle between the two wheels as seen in (fig.2).
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> ![IMG_0537](http://gitlab.au.dk/uploads/group-22/lego/ef9e0aa588/IMG_0537.JPG)
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> #### Fig. 2 - Our robot with the fixed axle between the two wheels.
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> ##### Black and White results:
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>The results show that the sensor is able to distinguish black from white under both dark and bright light settings. With "Black White Difference" the table shows a significant difference above 20 for all black-white readings. It also shows that the surface did have a small impact on the readings as the "Black White Difference" changed according to the surface. It is also worth to notice that the "Black White Difference" was generally larger under bright light settings.
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