Science Buddies: "Ask an Expert"

(Posted on behalf of parent/students - Project: https://www.sciencebuddies.org/science- ... obotic-arm)
------------------------------------------------
Popsicle Stick Robotic Arm

Trying this little project with my girls for Easter break. However, we are getting twitching/ fluttering from the servo motors. What could cause that? Also, when we use your 9v battery with the kit- it provides no power. I’m having to use the USB cord into the comp for power. How can I get the 9v to allow power up?

David

Hi David,

How recently did you install or update the Arduino IDE? There was a bug in the servo library that controls the servo motors at one point, but I believe it has been patched, and shouldn't be the source of the issue if you just installed the IDE for the first time when doing this project. Can you let us know:

1) What version of the IDE you're running (should be at the top of the window when you open it, e.g. mine says Arduino IDE 2.3.5)
2) What version of the servo library you have? Go to Tools -> Manage Libraries, search for "servo" and it should pop up on the left. I have version 1.2.2.

For the 9V battery - can you try disconnecting the servos and running the "Blink" example code (File -> Examples -> 01.Basics -> Blink) which should blink the onboard LED? That will help us tell whether the 9V battery is literally not powering the Arduino at all, or just having trouble powering the servos. If the blink example code works, can you then try a fresh 9V battery with the servos if you have one available? Motors use a lot of power and may drain the 9V pretty quickly, so ultimately it might be best to run this project off wall/USB power for extended use.

Hope that helps, please write back if you have more questions.

Ben