Skip to main content

NXT Sensors - Adventures in Color Detection

I was recently playing with the T-56 Robotic Arm (from the Mindstorms Kit). My son (he's 5) built about 65% of the robot.

We created the default program… it grabs a ball, and if it is red, it turns and drops it on the ground. If it is blue, it puts the ball back on the stand.

My son wanted to try some other colors with it. So we started with the Red and Blue ball, and added a Green ball, a Yellow ball and an Orange ball. My son had an old play set from when he was 2. It had the three colored balls, and they are the same size as the two that come with the NXT system.

On to the Adventure!

TIP: Check your light source first, since different amounts of light will give you a different reading.

If possible, try and use colors that are farther apart on the color spectrum. Close colors often have a close light value, and even that can vary slightly if your object is moving or the reading is not taken in the same light every time.

We used the colored balls and came up with the following readings:

  • Blue = 21
  • Red = 57
  • Green = 47
  • Yellow = 60
  • Orange = 53

As you can see, many of the colors are close in their readings on the NXT Light Sensor. This makes determining the colors a bit tricky. Furthermore, the NXT Light Sensor uses a red LED to illuminate the object when it takes a reading. This frequently made the yellow ball register as red. And the red ball was sometimes identified as orange.

When we finished, we used the blue, green, yellow and orange balls. The program would pick up a ball and say the color. If it was yellow, it would turn to the 2nd stand, say “Watch Out!” and drop the ball. Any other color and the arm would just say “Whoops!” and drop the ball on the original stand.

Nothing super fancy, but my son liked it. He kept running it over and over and just changing the balls.

I plan on trying a different programming environment soon. The LEGO stuff works good for the simple projects, but after 4 color choices, a couple of sound effects and moving the motors… I ran out of space on the NXT brick. :(

Popular posts from this blog

Celebrating MINDSTORMS with a Remix - Part 3

The ROBOTMAK3RS continued their celebration of the 25th Anniversary of MINDSTORMS through these Fall and Winter remix projects. Each ROBOTMAK3R was tasked with selecting one LEGO set of their choice and combining it with a MINDSTORMS set. Below are the five amazing models they came up with. Braill3 by Jerry Nicholls Braill3 is an EV3-based LEGO Braille bricks reader. This robot uses its fingertip, made from three touch switches, to read messages written using the LEGO Braille bricks and will speak out what it detected. If it sees a simple maths problem it will attempt to solve it and give the answer as well. To learn more about the process of creating this machine, read Jerry's blog . Braill3 can be viewed here . Set Review: The Braille Bricks set is well thought out. The ratios of the letters is suitable for general use and the addition of some punctuation and arithmetic operators is excellent. There is a card showing what bricks there are and their quantities, but no form of sort...

Celebrating MINDSTORMS with a Remix - Part 2

The ROBOTMAK3RS continued their celebration of the 25th Anniversary of MINDSTORMS through these summer and fall remix projects. Each ROBOTMAK3R was tasked with selecting one LEGO set of their choice and combining it with a MINDSTORMS set. Below are the five amazing models they came up with. Remote controlled material handle r by Jozua van Ravenhorst (aka Mr Jo) This remix combines the LEGO Technic Material Handler (42144) with MINDSTORMS EV3 (31313) It uses the power of pneumatic cylinders to move objects around. By using a bluetooth remote control, very precise movements can be made with this model. Touch sensors in the base chassis prevent the turret twisting the cables that go through the turntable to much. The program has several protections to prevent over pressurizing the system for each of the 3 individual pumps and valves that control the 2 booms and claws. The real version of this machine is mostly used in waste material sites to bring the material to machines that sort and...

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...