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I'm making a simple program with LEGO EV3 Education. It makes a little tank to follow a black line over a white-ish floor.

Here it is:

[enter image description here]

This works very smooth: it makes the tank follow the EDGE of the line and substantially takes in account the amount of light the sensor recevies. Black is 11, White is 75: if the light is near 75, then take the power of the B (left) motor higher than the C (right) motor. if the light is near 11, then take the power of C motor higher than B. Otherwise, make C and B power similar.

I want now to add some output on the display, like this:

enter image description here

The idea is: if B power is between C+10 and C-10, then show a forward arrow. else if: if B < C show Right arrow, else Left arrow.

Problem is that, adding this code, the tank doesn't move straight anymore! C and B motor ,on a stright line, alternate power making the robot zig zagging the line.

Why does an output operation on the display affects motors power?

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1 Answer 1

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Because it takes time to write to the display. The motor speed cannot be changed until the display blocks have finished and your loop repeats.

Try this instead... create a second loop in parallel to the first that handles the display. You will need a new logic variable to send information from the motor loop to the display loop.

first two loops third loop

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  • I tried, same result! What do you mean with "new logic variable"? I used the same "B-Power" and "C-Power" variable that I'm using in the main motor loop
    – Simone Chelo
    Commented Mar 4, 2016 at 8:50
  • I have added screenshots to show what I mean. I imagine that it would be better to move the math blocks from the motor loop to the display loop, then you wouldn't need the "Forward" variable.
    – David Lechner
    Commented Mar 4, 2016 at 18:54

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