This miniball project has its roots in the old BEAM Miniball kit published by Solarbotics. It's still a cool kit, so we're going to show you how built a simpler version. This project is spearheaded by Mr. Jerome Demers ( aka Robomaniac ), our intern at Solarbotics!
This robot uses a solar engine circuit. A small solar cell by itself generally doesn't have the power to make a motor move, so you have to store this power up in a capacitor, which is a small battery-like storage device. When the circuit sees that there is enough power stored, it releases it in a burst to the motor, getting useful work.
With this project, our solar engine will be powering a small car in a large plastic sphere!
This technology of using minimal electronics and simple mechanical design is call BEAM robotics.
The Miniball itself was originally invented by Richard Weait of North York, Toronto.The Miniball is a amazing robot - it uses a simple circuit and the robot itself proves to be very capable, rarely getting stuck. The Miniball is mechanically complex and electronically simple. (But don't worry - the mechanical part is still pretty easy)
In this case, we aren't going to build the original Miniball, but a smaller, more basic wannabe version. This robot is extremely simple and can take a beginner less than 2 hours to build.
The original Miniball has a geared motor that moved as a counter weight around a fixed shaft inside the plastic ball container. As the motor tries to move the weight forward, the ball starts to roll in that direction.
In our case we have a motor with wheel, which spins the ball forward as it runs.
Imagine this like a hamster in a ball - it's almost the exact same thing! But in this case, we're feeding our hamster with photons!
1 - Transparent Plastic Sphere (80mm - get from craft store or hobby shop)
1 - High-efficiency Coreless Motor (Solarbotics part #: RPM2)
1 - Motor Mounting Clip (Solarbotics part #: MMFC)
3 - Rubber Wheels on Nylon Hubs (Solarbotics part #: RW)
2 - Paper clip
1 - 37 x 33mm Solarbotics Solar Cell (Solarbotics part #: SCC3733)
1 - 0.35F 2.5V Capacitor (Solarbotics part #: CP.33F)
1 - 6.8uF Tantalum Capacitor (Solarbotics part #: CP6.8uF)
1 - 3904 Transistor (Solarbotics part #: TR3904)
1 - 1381 Voltage Trigger (Solarbotics part #:1381C)
1 - Signal Diode 1N914, 1N4148 (Solarbotics part #: D1)
1 - Length twisted red/black wire
- Soldering equipment (soldering iron / solder / cleaning sponge) (HVW tech soldering tools)
- A pair of Needle-nose pliers (HVW tech part #: 43060 or 43061)
- A pair of Flush Cutters (HVW tech part #: 43040)
- Safety Glasses - VERY important when clipping and snipping! (Solarbotics part #: 5330)
We made a parts bundle of everything you you need to build this project (not including the plastic ball and hand tools). You'll have all the mechanical and electrical components to start making this neat lil' robot!
Follow the instructions on the printed circuit board - there are labels that mark where various components go. Note how we used the sleeve of a breadboard wire to isolate the positive (+) lead of the capacitor, preventing it from contacting the diode.
What we do here is simply cut one large wheel into two smaller wheels. It's a way to recycle and save parts at the same time.
This is how you do it: Take a sharp blade and slide along the object you want to cut. Roll with the wheel and press down at the same time. You'll cutting through easily. Don't press too hard. Roll it back and forth 4 or 5 times with gentle pressure to make a nice cut.
You can use this technique on metal tubing too! It works very well!
We are now ready to attach the wheel frame to the solar cell. You can do this with glue, but solder is much better!
I will solder my frame to the fat metal strip on the back of the PCB, but it is covered by a green coating. Scratch the surface of the PCB (like in the picture) to create an exposed patch where you can solder on a breadboard wire.
If you want, epoxy your wire here instead. DON'T USE HOT GLUE! Hot glue will get soft and melt in the warm insides of the clear ball, especially in sunlight!