Space is very limited in which to catch the balls emerging from the delivery chute, and so I purchased from a craft shop 4 plastic boxes to use as receiving bins. These boxes came from the Really Useful Box Company, www.reallyusefulbox.com They have a capacity of 0.07 litres and dimensions 90 x 65 x 30 mm externally and 61 x 48 x 24 mm internally. They are also advertised on Ebay sites. In order to hold the boxes in the appropriate positions, I made a framework out of remaining pieces in the Lego Set. This is functional rather than pretty! Also, experiment showed that the balls could easily bounce off the hard bottom of the boxes and jump out of the boxes again. This was solved by making a soft landing bed and end stop for each box, by folding up a couple of paper table napkins and cutting them to size. Note the vertical "pillow" section at the end of each box. The whole array still requires careful positioning, but with care it is possible to ensure that all the balls end up in the correct places. Two orange flippers on the end of the delivery chute are positioned to deflect balls into the red and blue boxes.
The upper ball track can hold 11 out of the twelve balls, but 10 is probably the maximum number to load at one time. It is possible to drop extra balls onto the track as the model is running if you want to keep it going. To stop the balls binding, flex the side walls of the track outwards when you have built the model. Also, ensure that the upper track lies flat against the top of the gate motor by adjusting the bracing 12 length axle, which will have the top support right at the end of its length.
You can click here to see pictorial representations of all the programs and blocks discussed. The programs can be downloaded from the links on the left. Each zip file contains the separate programs and the blocks and also pack and go versions of those programs which use the blocks.
I hope you have fun building this second version of the model and testing it. I would appreciate any feed back to
robin dot newman at gmail dot com
Recently I came across another colour sorter bot on youtube here. I have developed my own version based on this video and you can see details of it on the navigation pane as version 3. This is a simpler bot and doesn't take long to build. It uses parts only from the 8547 NXT2 set. There is a Notes page within the instructions pdf which gives help in setting it up, and a pictorial representation of the program on the Program Pictures page. There is also a link to download the sorter3.rbt file. I am indebted to the YouTube user DrCEM1 for the idea. It was interesting reverse engineering a robot from the video!
Version 4 follows on the next page