Skip to main content

NXT Peg Sorter


This NXT Peg Sorter will sort long black NXT pegs from long gray pegs, into two separate bins. A conveyor feeds pegs down in a chute, then the light sensor is used to see the color of the peg as it is sliding down the chute, then a hitting arm hits the black pegs to the side while allowing gray pegs to fall straight down into the other side.

Here is a video of the machine in action:

There are simpler and more reliable ways to sort pegs, but with this project I wanted to do something similar to the way some modern high speed mechanical sorters work in factories. In some of these machines, the items are thrown quickly past a gap in the conveyor belt, where an optical sensor looks for rejects, and then air jets are used to knock the rejected items down through the gap into a reject bin, while the good items continue past the gap to the other side. The challenges are to quickly detect a reject and then to get the right timing between seeing the reject and pushing it out of the fast moving stream. An example is this machine for sorting vegetables (see also the video at the end of the page). Another example that is simpler and closer to how this peg sorter works is seen in this video of a colored pencil sorter.

In this NXT Peg Sorter, the gray pegs are the "good" pegs, and the black ones are the "bad" (e.g. burnt) ones that need to be rejected. The speed of this sorter is limited by how fast the hitting arm can recover after hitting one black peg (not nearly as fast as an air pressure jet can recover), but the rest of the machine is capable of sorting much faster. I didn't put that much time into designing a good hitting arm, so there is definitely room for improvement here. How fast can it get?

Popular posts from this blog

MINDSTORMS Retires!

2023 is the 25th Anniversary of the MINDSTORMS brand. For 25 years, MINDSTORMS has educated and inspired a generation of robot builders, both children and adults. Unfortunately, the LEGO Group decided to end the line on December 2022. Many ROBOTMAK3RS have been passionately involved with the development of MINDSTORMS through the MUP and MCP programs. Even with the newest Robot Inventor line, several ROBOTMAK3RS were invited to submit additional bonus models that were included in the official app. Regardless of the retirement of a major LEGO robotics product line, ROBOTMAK3RS continue to MAKE-SHARE-INSPIRE using all LEGO robotics platforms available to us. Here is the official statement from LEGO. Since its launch in September 1998, LEGO MINDSTORMS has been one of the core ‘Build & Code’ experiences in the company’s portfolio, carrying with it significant brand equity and becoming a stand-out experience for the early days of consumer robotics and leading to current Build & Code

Celebrating MINDSTORMS with a Remix Part 1

In honor of the 25th Anniversary of MINDSTORMS, we asked ROBOTMAK3RS to combine a LEGO set of their choice with a MINDSTORMS set. Here is what these five ROBOTMAK3RS came up with.  MINDSTORMS Chess Assistant by Arvind Seshan Overview: When you are new to chess, it can be a challenge to remember which pieces go where. Now, you can use machine learning and LEGO MINDSTORMS Robot Inventor to build a tool to help you learn where all the chess pieces go on the chess board. Sets used: LEGO® Iconic Chess Set (40174) and MINDSTORMS Robot Inventor (51515) Review: I really like how the chess set base can store all the pieces underneath and that the board neatly splits in half for handy storage. The chess pieces themselves are very sturdy and well built. My only criticism is the building of the box itself. It was quite difficult to see what pieces to use and since the entire box is made mostly of thin plates, it took a lot of time and patience. I would have liked the storage area to be sliding dra

Celebrating 25 Years of MINDSTORMS

In celebration of the 25th Anniversary of MINDSTORMS, we take a trip through history. Please also visit ROBOTMAK3RS Community every week as we highlight different projects all through 2023 in celebration of the anniversary. Some of the early history is based on the content shared by  Coder Shah  in our  MINDSTORMS EV3 Community Group . Some of the text and links may have been edited from his original posts for consistency and clarity.  1984 - Kjeld Kirk Kristiansen watched a TV program called "Talking Turtle," where MIT professor Seymour Papert demonstrated how children could control robot "turtles" using LOGO, a programming language he developed. 1988 - The collaboration between MIT and LEGO resulted in LEGO TC Logo in 1988, which allowed students to control LEGO models using computer commands. The video shows Papert demonstrating TC Logo. 1990 - LEGO TC Logo was hampered since the robots you built had to be tethered to a personal computer. LEGO and MIT