This simple solar robot project utilizes a solar engine circuit. The small solar cell can’t generate enough power to move the motor, so what the miniball does is store the power in a capacitor. When there’s enough power stored, it releases the power into the motor to make the ball move around.

The mechanical parts you’ll need for the solar powered miniball are:

  • 1 – 80mm transparent plastic sphere (You can buy this from a hobby shop or arts and crafts store.)
  • 1 – High-efficiency coreless motor*
  • 1 – Motor mounting clip*
  • 3 – Rubber wheels on nylon hubs*
  • 2 – Paper clips

The electronic parts are:

  • 1 – 37x33mm Solarbotics solar cell*
  • 1 – 0.35F 2.5V Capacitor*
  • 1 – 6.8uF Tantalum capacitor*
  • 1 – 3904 Transistor*
  • 1 – 1381 Voltage trigger*
  • 1 – Signal diode 1N914*
  • 1 – length twisted red/black wire
  • *  parts sold in bundle by Solarbotics (Click here to get the bundle.)

The tools needed for the solar powered miniball DIY project are:

  • Soldering iron
  • Needle-nose pliers
  • Flush cutters
  • Safety glasses

Here are the procedures for building the solar powered miniball:

  1. Solder all parts to the solar cell. If you bought the bundle from Solarbotics, it comes with  instructions regarding what to solder and where.
  2. Place the components on the printed circuit board, making sure you get the polarity of the capacitor right. This means putting the positive lead in the right hole. Also, use a sleeve of a breadboard wire to isolate the positive lead and prevent it from contacting the diode.
  3. Cut a wheel into two pieces.
  4. Straighten the paperclip and bend it to hold both wheels.
  5. Use a breadboard wire to make a guide for the wheels so that they will not slide too far.
  6. Place the rubber wheel and close the wheel guide.
  7. Use a fuse holder (included in the bundle from Solarbotics) to mount the motor. Use the pliers and squeeze the fuse holder over the wire so it will stay in place.
  8. Bend the paperclip frame so it will fit in the plastic sphere.
  9. Strip the insulation off the wire and save the sleeve. Push the sleeve into the motor and slide the wheel into it.
  10. Cip the motor in the fuse holder and place the assembly in the sphere.
  11. Solder the wheel frame to the solar cell.
  12. Use the snipping tool to cut the tabs off the sphere.
  13. Place the robot into the ball. You’re done!

This is how you make a DIY solar powered miniball. If your miniball flips upside down and stops moving, you can make a long paper clip and place it erect without touching the top of the plastic ball.