Monthly Archives: October 2014


LEGO EV3 Line Detection

One area to improve consistency for FLL is to use sensors.  I recently had a coach ask me about line detection and how to program it.  I know of three ways to program and teach line detection.

portviewFor the sample line detection programs, there is a color sensor in port 3 and the drive motors are in ports B and C.  Before starting to program, ensure the color sensor is positioned so it can detect color.  My team was having issues with detection this year and trouble shooting revealed the sensor was to low.   It should be about three pennies above the mat.  Use the port view to check if the sensor is detecting color.  (I will update the image with the color sensor).  Also watch your speed when detecting a line.  Start slow, fast speeds will sometimes miss.

Wait Block Line Detection Method


Steering block set to on.

The most basic line detection method is the wait block.  The wait block method has three blocks, a steering motor set to on, a wait block set to the color sensor and color compare, and a steering block set to off. Start with a slow speed and test your way up to a faster speed.


Wait block set to color sensor and compare color. The color is 5, red. Note the port number 3.

Steering block set to off, which makes it stop.

Steering block set to off, which makes it stop.

Loop Line Detection Method


The Loop Line Detection Method is very similar to a wait block and functions exactly the same.  The only difference is the loop replaces the wait block.  The loops exit’s condition is exactly the same as the wait block.


Recovery Line Detection Method



The Recovery Line Detection Method builds on the loop method but utilizes logic blocks and a rotation sensor.  It is designed to recover if the robot does not detect a line.  This method was developed by my Capital Girls Too team for the Senior Solutions green medicine bottle mission.  For the medicine bottle mission, the goal was to pick up the green medicine bottle and return it to base.  The catch was it could be in a different place.  My team soon realized if their robot did not line up correctly, it would not detect the green bottle and keep going.  Their solution was to measure rotations to make the robot return to base if the color was not detected.  It took a couple meetings and some understanding of the rotation sensor and logic block but they use it all the time now.  We even made a badge for it so they got rewarded when they used it.


Like the other line detection methods, the steering block is set to on.   The two sensor blocks, color and rotation, pass false to the logic block until their condition is true.  The logic block uses “or” logic, meaning it will pass true once the color is detected or the rotations are achieved.  Once a condition is met, the logic block pass true to the loop’s exit condition, which is logic, and the loop exits.  The last block is motor off.

It works with other sensors

The detection logic in the methods above will also work for the touch, gyro and ultrasonic sensors.   Once the team has an understanding of loop, switch and logic blocks, they can do amazing things.  Check out the program flow StartingPoints poster for teaching program logic.

Robot Nerds Needed

robotnerd1, a web application to simplify planning, organizing and sharing for robotics teams is looking for beta users.

To qualify for a free Robot Nerd T-shirt or sticker, participate in our private StartingPoints beta at  If prompted for a code, use ROBO.



Story Telling

One thing I love about FLL is story telling.   You have to tell stories about your robot, core values and project.  Tonight we have a team meeting where we will start developing our project story. We also meet with a technology expert to learn about NFC technology and makers programming.  They will actually be using an Arduino, an open-source electronics platform based on easy-to-use hardware and software.

The Capital Teens have meet with experts, done some research and developed an innovative solution.  Now it is time for them to figure out how to tell their project story.   They had the option of skit, puppet show, news show but early on the girls decided to stick with a doodle presentation.  A doodle presentation uses hand drawn slides with text, pictures and illustrations.  It is very simply but effective.  I think they like drawing.  

When they sit down to develop their story, we will use the project rubric as the outline.  It is very important for the story, whatever your presentation method, to convey the information in the rubric.  I remember the girls did such a good job with Senior Solutions, the judge said you covered everything.  With a story focused on the rubric, you have more time to talk about your solution.

So as your team prepares their project story, make sure to cover the items in the Project Rubric.



Robot Nerd Blind Challenge – Core Values Challenge Activity

We did a fun core values challenge, I’m calling it Robot Nerd Blind Challenge.  The challenge is to draw a picture based on descriptions.  It enforces team collaboration and teamwork.

The team had to select three people to be the eyes and the rest of the team would be the hands.  They eyes could view, describe and act out the picture but could not see what the team was drawing.  The hands could not see the source image and had to draw based on the eyes descriptions and actions.  They had 5 minutes.

Here is the source (eyes) image and what the hands drew.  It was a very fun challenge and the team learned some valuable lessons.   I was impressed with how they acted it out, which is why I select three eyes to see if they would pick up on this approach.  They learned to listen before acting and that each person needs a role.

If you want to try this with your team, here is a pdf download of the source image – StartingPointsDancingRobotNerds.

2014-09-26 21.05.462014-09-26 21.05.53












Robot Nerds Needed

robotnerd1, a web application to simplify planning, organizing and sharing for robotics teams is looking for beta users.

To qualify for a free Robot Nerd T-shirt or sticker, participate in our private StartingPoints beta.   Email and include your team name and location.


2014-09-30 21.05.31

Center of Gravity

One challenge my team faced was a front heavy robot.  When it stopped fast, it was like a wild bronco and the back would kick-up.  After they realized the issue and its impact on consistency, they started looking for solutions.   Thanks to Wally’s site, I had some 2 x 6 x 2 “heavy crane” bricks, LEGO part number 73843, that weigh 2 ounces each.   The girls added two bricks, 4 ounces, and now it is not front heavy.

Checkout Wally’s site,