Skip to main content

Vending Machine for NXT 2.0

This Vending Machine project is one of the "bonus projects" available on the CD LEGO MINDSTORMS NXT 2.0 by Example from A preview and video of the project are available on the website (see video below), and full building instructions and the fully commented NXT-G program are available on the CD.

Built with a single NXT 2.0 kit, the machine displays four LEGO parts for sale on the rack in front. The colored balls act as different coin values, with the color sensor detecting them as they are inserted. Using the display and buttons on the NXT, you choose your item from a menu on screen, then you insert balls to pay for it. If you inserted enough money, the selected item is dispensed down the slide in the front, and if you inserted extra money, the machine automatically computes and dispenses the correct amount of change via a hidden change reservoir into the change cup in front. The machine also handles various other error cases such as not inserting enough money, inserting too much money for the change reservoir to handle, and invalid coins. The user can cancel a transaction via a "coin return" lever, which returns the coins inserted and informs the machine via a touch sensor.

The program is in NXT-G, and since the task is longer and more complex than a typical NXT-G program, it is split into several My Blocks to break up the task into various parts, such as processing the on-screen menu, detecting coins, computing change, handling errors, etc. The My Blocks that process the on-screen user interface are "general purpose" (not specific to the Vending Machine project) and could be re-used for similar user-interface tasks in other programs.

Here is a short video of the Vending Machine doing a transaction:

Popular posts from this blog


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 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

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