The Newton´s pendulum is a device that demonstrates conservation of momentum and energy. A typical Newton's cradle consists of a series of identically sized metal balls suspended in a metal frame so that they are just touching each other at rest.

Instead of buliding such device, I thought to build an idealized 5-LED-ball Newton´s cradle desk-toy using a microcontroller. The strikes between balls is simulated by two micro servo motors.

I have included a potenciometer to adjust the frequency of the movement and a button to switch between the two run modes availables.

I hope you like.

Step 1: List of Material

The list of material is the following:

ARDUINO MEGA 2560 R3 or compatible ARDUINO MEGA 2560 R3 microcontroller
Protoboard 480
2 micro servo motors
5 ping-pong balls
5 RGB LED (common anode)
15 220 ohmios resistors
1 10K ohmios resistor
1 potenciometer
1 button
Metal tubes
Methacrylate
Wooden rods

Step 2: Building a RGB LED Ball

STEP 2.1 Cut a little piece of wood and drill 4 holes (PICTURE 1)

STEP 2.2 Insert the RGB led terminals in the holes (PICTURE 2)

STEP 2.3 Drill a hole in the ping-pong ball (PICTURE 3)

STEP 2.4 Solder a cable to each RGB led terminal (the black cable is the anode) (PICTURE 4 and PICTURE 5)

STEP 2.5 Cut a 8 inches piece of tube metal and pass the cables inside it (PICTURE 6)

STEP 2.6 Build a white paper cone to cover the weldings (PICTURE 7)

Step 3: Building the 5-ball Newnton´s Cradle

STEP 3.1 Cut a wood piece to place the metal tubes of the cradle (PICTURE 1)

STEP 3.2 Cut a methacrylate piece following the drawing in the PICTURE 2

STEP 3.3 Paste the methacrylate piece over the 4 metals tubes (PICTURE 3)

STEP 3.4 Paste the ball number 2 (PICTURE 4)

STEP 3.5 Paste the balls number 3 and 4 (PICTURE 5)

STEP 3.6 Paste a micro servo motor for the ball number 1 (PICTURE 6) and fix the metal tube as you can see in the PICTURE 7

STEP 3.7 Repeat the step 3.6 for the ball number 5

Step 4: Connecting Everything

Over the piece of methacrylate you have to mount another one where you will install the microcontroller and the protoboard (PICTURE 1)

You see that we will have 5 ping-pong balls numbered from 1 to 5 from left to right in the PICTURE 1. So you have to install 3 220 ohmios resistors for each ball on the protoboard as you can see in the PICTURE 2 and connect the cables from each ball (Red cable, Blue cable, Green cable and the anode terminal) as you can see in the PICTURE 3

On the PICTURE 4 you can see a detail of the potenciometer and the button.

The potenciometer allow us to change the frecuency of the movements and the button to switch between the two functions mode programmed.

I have included the drawings for the connection of each RGB ball, the connection of the potentiometer and the button following the sketch I have programmed.