Brick Mixer

Since the first version of my card reader, I intend to use it to program the order of brickes in a "brick mixer", taking bricks of different colors and outputting an ordered flow of bricks. I wondered for a while how to achieve this using only three motors... but finally succeeded, two of the motors performing two actions.

The brick mixer has four main parts:

• The brick feeder, that supplies 4 kind of colored bricks
• The card reader, which determines the order of the bricks in the output flow
• The conveyor belt that outputs the bricks streams
• The picker arm, that takes bricks in the right chute of the feeder and place them on the conveyor

Since the conveyor and the card reader uses one way motion, I used a differential and two ratchets to power the card reader when the motor turns forward and the conveyor when it turns backward. The micromotor of the picker drives the grip through a fast acting rubber belt, which slips while the micromotor goes on driving the gears to lower/lift the grip.

The carriage of the picker is guided by the front rail, and pins in that rail define stops position (one in front of each chute + on in front of the conveyor) detected by a touch sensor. In order to have a fast motion and good precision, the carriage goes past the pin because of inertia, then comes back on the pin. The pin of the conveyor is bigger so that the dropped brick is well centered.

Coding the card

With the color order of my brick mixer, each color is coded (in binary) as follow:

00 = Red brick (chute nearest of the conveyor)
01 = Gray brick
10 = Black brick
11 = Yellow brick (chute furthest of the conveyor)

Since the card reader reads a 15 bits word, I used the 14 lower bits to encode the color of 7 bricks, while the 15th bit is a "continue" bit: when the card contains 0 in this bit, the brick mixer stops after placing the 7th brick. If its value is 1, the brick mixer asks for another card, reads it and stores 7 other bricks. The first brick is coded as the 2 least significant bits. Example:

Order	Continue	7th brick	6th brick	5th brick	4th brick	3rd brick	2nd brick	1st brick
To code	No	Yellow	Black	Yellow	Gray	Yellow	Red	Yellow
Bin. value	0	11	10	11	01	11	00	11
Hex value	3		B		7		3
Dec. value	15219

Plug in this value in the Card Reader 2 basic program to obtain the plates colors of the card: B Y G Y G B G Y B G Y G B Y G Y

• Brick mixer in action: QuickTime movies

• Download the source file.
   

• See step-by-step instructions
  

• Download the LeoCAD design files

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