Finally it is there: Brick Sorter 4. As you can see it can sort 10 types of bricks, 5 colors and 2 sizes. The goal was of this machine was to improve Brick Sorter 2. To see what it can do, watch the video and/or take a look at the pictures below. There is also a description of the 'color sensor'.

	Let's start at the top. This is where the bricks are inserted. Instead of having to insert every brick manually, one by one, you can just throw a hand of bricks in the machine, and it will do the rest. The conveyor belt will only turn if there are not enough bricks in the brick chute. A light sensor detects this (Picture below). Once a brick has left the conveyor belt, it continues its way to these two wheels. They will get the brick in the right position for the loading chute. The red wedge you see is used so that bricks can't get in the brick chute while they are on their side. If there was no wedge, bricks would get stuck in the loading chute.
	In this picture you see the light sensor which detects if there are enough bricks to sort. If not, the machine simply turns on the conveyor belt. You also see a 'pusher' (below the green brick). This small but useful thing feeds bricks to the color sensor module. It will always feed one brick, even when there are two small bricks. (So that it can't confuse two small bricks for one large brick.)
	Right here you see the actual sorting part. Once a brick is fed by the 'pusher', it will go to the part that analyses the bricks. (How the color sensor works is explained below.) Once the machine knows what brick has to be sorted, it will move the depositor slide to the right position. This depends on the size. Then it will move the module with the 10 bins to the right position. This depends on the color. Once all that is done it opens the 'lock' (Explained below). The brick will fall in the correct bin. The picture on the left was taken just after sorting a large yellow brick. The lock is still open.
	This is the 'eye' of the machine. It is usually covered by some LEGO parts, so that there is no trouble with incoming light. These parts were taken away to take a picture. From the left to the right: The LEGO lamp, a phototransistor, housed in a LEGO brick and a normal RCX light sensor. If the light sensor on the right detects something, this means that there is a large brick inside. The other two components detect the color of the brick. The lamp sends out light, and the phototransistor measures the amount of reflected light. The amount of reflected light depends on the color of the brick. This way the machine can 'see' color.
	On the left: The lock is closed, it is ready to scan a brick. On the right: The lock is open, the brick has been identified and it will fall in the correct bin.
	This motor controls the module with the bins. Using the internal rotation sensor it can move to the right place, depending on the color.
	This 'sensor' allows the NXT brick to talk to the RCX. It can be ordered at Mindsensors.
The RCX has 4 programs on it. All these programs perform a certain action. The NXT is master. The NXT lets the RCX run the required program using the infrared link. The programs can be downloaded here.