As I have a long record of building color sorters...
for RCX, NXT
and now for EV3! SORT3R can be built with a single 31313 EV3
set. Well, almost! The kit contains a capable color sensor,
but no colored elements to use with it... So for SORT3R I used
ubiquitous 2x4 bricks, in 6 colors: black, blue, red, yellow,
black and white. EV3 color sorter is also able to detect brown,
but the EV3 kid doesn't contain enough parts to build a seventh
bin (and the sensor is a bit less reliable on brown, sometimes
confusing it with black). A bit improvement of EV3 color sensor
over NXT one is that it is able to detect "nothing",
SORT3R is thus able to detect that there is no more brick in
Right side view.
Left side view.
The brick chute and sorting bins.
SORT3R needs to be positioned very
precisely on the chute to be able to work reliably.
It is guided by the L2 beams on top of the bins
structure that slide between the two rails on the
In the other direction the IR sensor reads (with
excellent precision!) the position of the back of
the white panel near the chute. The bins are wide
enough so that positioning with rotation sensor
only is enough to drop the bricks in the right place.
The position is recalibrated before picking each
The last bit needed to achieve pick up reliability
was to compensate for the position of the brick
itself that tended to slide a bit laterally at the
end of the chute. The two wheels on sides of the
arms put it gently back in place...
After testing a lot SORT3R, I discovered that
sometimes it bumps into the chute when bringing
a brick to sort bin. Indeed, the gripper arms come
very close to the ramp, as shown on this image.
If you have spare axlepins, the best solution is
to flip the L beams on sides of color sensor. This
gives a little more margin and avoids the problem.
...otherwise, just make sure that IR sensor assembly
(and guiding rails) is not fully pushed in place.