Introduction: Solar Powered Miniball Wannabe

Picture of Solar Powered Miniball Wannabe

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!

Step 1: Parts You'll Need

Picture of Parts You'll Need

Mechanical Parts
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

Electronic Parts
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

Tools Required
- 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!

Click this link to get the bundle.

Step 2: Making the Circuit

Picture of Making the Circuit

The first thing to do is solder all the parts to the solarcell. If you are not using a Solarbotics solarcell, you will have to find the "freeforming" instructions for building a solar engine circuit.

Solarbotics solar cells all come with a circuitboard ready-to-use on the backside of each cell.

Step 3: Solder the Circuit

Picture of Solder the Circuit

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.

Step 4: Make Two Wheels From One

Picture of Make Two Wheels From One

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!

Step 5: Wheel Holder

Picture of Wheel Holder

We're now going to take a paper clip and bend it, creating a wheel holder for both wheels. Just cut at the last step.

Step 6: Wheel Guide

Picture of Wheel Guide

Use breadboard wire to make a guide for the wheels. This will prevent the wheel from sliding too far.

(Check the next step if this doesn't quite make sense yet...)

Step 7: Closing the Wheel Guide

Picture of Closing the Wheel Guide

Simply close the guide so that the wheel doesn't fall off the axle.

Step 8: The Motor Mount

Picture of The Motor Mount

Here's a clever way to mount a motor to your robot - these pager motors are really small, and they fit perfectly in fuse holder.

We'll use a fuse holder (included in the parts bundle for this project) to mount our motor. Don't solder directly to the motor - this is pretty difficult, and you can ruin the part.

I used pliers to "squeeze" the fuse holder's legs over the wire, so that the wire stays in place while soldering it to the paper clip frame.

Step 9: Bend the Frame

Picture of Bend the Frame

Since this will go into a ball, we need to make the frame fit inside of it. We'll bend the frame run along the contour of the shell, and lower the center of gravity.

It is best to have your sphere on hand to you can play with the wire's bend geometry.

Step 10: Inserting the Wheel Onto the Motor

Picture of Inserting the Wheel Onto the Motor

You've probably noticed that the inside hole in the rubber wheel is too large compared to the motor shaft.

This is a neat way to insert the wheel to motor shaft. Just take a piece of wire sleeve and insert in onto the shaft, creating a snug fit with the rubber wheel.

Step 11: Clip the Motor to the Frame

Picture of Clip the Motor to the Frame

Here we clip the motor into the fuse holder, completing the frame. Place the whole assembly inside the half-sphere.

Now you're ready to mount the solarcell to the frame!

Step 12: Mount the Wheel Assembly to the Solar Cell

Picture of Mount the Wheel Assembly to the Solar Cell

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!

Step 13: Preparing the Ball

Picture of Preparing the Ball

Take the plastic ball and cut the tabs. Be very careful with your cutting here, as you don't want to break the ball.

Use the snipping tool and slowly cut in a circle until the tabs are removed. Start clipping far out, and work in. Snipping too close to the sphere's edge might crack it!

Step 14: Insert Robot Into Ball

Picture of Insert Robot Into Ball

Take your robot and put it into the plastic ball. Et voila, you're finished!

Be sure that the robot rolls in the ball without friction. You might need to bend the paperclip to make the robot work perfectly, with no rubbing.

Now go try out your new robot!

Here is a quick test, make your robot roll into a wall...

You will probably realize that it flips over in the ball. It goes so fast, that it flips itself over and is now stuck upside down!

Check next step to fix that issue.

Step 15: Statbilization Improvement

Picture of Statbilization Improvement

To prevent the robot from flipping upside down, you can make a long paper clip rod that comes close to touching the top of the plastic ball.

Just like in steps 6 & 7, take a paper clip, add a rubber wheel at the end, and then solder everything to the bottom of the paper clip frame. All done!

Step 16: What Is Next...

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Kelly Smith (author)2014-02-08

Boo - not working. Diode is correct; used a magnifying glass to inspect my soldering and I don't see any overflow. Switched motor leads but then read elsewhere that just changes the direction of the motor. Tested the motor again and it works. I am using a 1381e instead of 1381c but didn't think that would matter. Thinking it has to be a short and I just can't see it. How do I test? Thanx all.

Kelly Smith made it! (author)2014-02-02

Thanx for the easy follow along!

niallthemagicone (author)2014-01-16

very cool

imbiglarry (author)2013-11-04

Too cool.

clarkwerton (author)2013-10-30

I really have to try making one of these!

pcastro5 (author)2012-12-20

Ok. Can I use hook-up wires instead of using breadboard wires. If I can't. Where can I buy a breadboard wire?

Caquin (author)2011-09-02

Working on this with my 10 year old.
Heads up on the breadboard wire. This is not in the parts list but it is essential to keeping the wire from contacting the board.

We are headed over to Radioshack to find some breadboard.

Stephen D. Alverez (author)2009-11-17

 how do you get the ^sphere^

I when to my local art store, they use those sphere for home made Xmas ornaments.

They are really cheap, they where on sales for 0.99$

They had 2 size, small like the one in this instructables and much bigger. (4 inch )

have fun!

riverreaper (author)robomaniac2010-01-05

opps missed can you come here an read up one , oh ill copy an paste would a square work or does it not power enoght to flip over?

jwoo2023 (author)riverreaper2011-04-09

i dont think it will have enough power so try using the ball/capsules from the toy dispenser thingys.

riverreaper (author)robomaniac2010-01-05

i hate being dumb an lazy could we just trade ive lots of stuff taken apart lol you could build amys , live vid cam races sounds fun , oh wait it rains here to much .

riverreaper (author)riverreaper2010-01-05

how many workerballs can i get for 50,to 100 ft of cable wire , my dad collected junk too lol

arts an craft stores sell the P.balls , would a square work or does it not power enoght to flip over?

cyprian916 (author)riverreaper2010-07-27

here's the one i bought

Shrio404 (author)2011-01-06

Adding up totals now... im at around $23 for electronics and another $11 for sphere

jmhn (author)2010-11-28

Will the robot work in artificial light?

pobturtle (author)2010-09-03

How much do all the part cost?

cyprian916 (author)2010-07-27

this is sick!!! i'm Definitely building one.

airecrist (author)2010-06-17

" cant you tell when someones joking " um yeah its text so it's kinda hard to tell whos joking and whos not....which is why they created emotes..... " look how lazy you are replieing stupidly 5 months latter"\ hardly lazy... just saw this page the other day which is when i commented, and as for how long the comment was up for no clue don't pay enough attention as to when people post as to what they post

riverreaper (author)airecrist2010-06-24

you said why im on this sight if im lazy so i took a look at your an thats my coment on how much work you put into it , du , you one of them whom just loioks for resons to fight or put some one down , to make yourself look better ...but most can see by how much work youve put into doing instructables yourself by going to your sight . im on here because im an inventer at heart , not to buy an over priced item , that a 6.00 cat toy will do

robomaniac (author)2010-06-21

For a limited time only, get the Solar Powered Miniball Wannabe for 3 easy payment of 320$ and GET FREE SHIPPING! ps- I am not kidding

riverreaper (author)robomaniac2010-06-24

thats ok ill wait till gas gets cheaper an go back to wipen out our ozoin layer

airecrist (author)2010-06-14

if your lazy why are you on this site?

AustenQn (author)2010-03-23

Is there a remote controll?

JingleJoe (author)2009-11-24

Can I get a circuit diagram for this?

JingleJoe (author)Solarbotics2010-02-24

Spiffing, thankyou :)

Mdob (author)2009-11-26

Hi i was wondering if you could use a 1F cap instead of the 0.35F; would it just take longer to charge and have a longer burst of power?

Thanks for your help

Solarbotics (author)Mdob2010-02-24

 yes it will have longer burst but will take longer to charge.

mimib1230 (author)2009-12-21

This is great so far! The only roadblock I've come across may sound amateurish but this is new to me:

I bought the bundle from the website. I can't tell the difference between the two black pieces (the transistor and the voltage detector) to be able to know where they go. Any advice? They are not labeled at all.

Solarbotics (author)mimib12302010-02-24

 I never say non label transistor! I check the roll of the 2N3904 and 1381 and they are both mark.

The 1381 is writting 381, the 1 is really hard to see/missing.

You can test the transistor because there is a diode between the base and emitter.

Take you multimeter in diode mode, then put the component flat side on the table. Touch the middle pin and the right pin with your multimeter and you should read around 0,6V. If you don't that is the 1381. 

Good luck!

caver01 (author)2010-01-10

 Mine does not work. I am measuring a short across the leads of the .35F cap and I get a short. Bad cap?

Solarbotics (author)caver012010-02-24

How do you measure your short? With the beeper on the multimeter or ohm?

I used the beeper and I heard a beep too! I took the ohm and got 4M on a 4700uF cap. 

Be sure to check all the connection and polarity of all the components.

jwystup (author)2010-02-20

When I finished my "miniball wannabe" it didn't work. After staring at it for awhile and looking at the setup of the <a href="">Solar Powered Battle Symet</a>, I realized that I put the diode on backwards. I wanted to note to anyone else trying this instructable that the diode needs to have the dark line towards the bottom (in the orientation of the picture above)

Solarbotics (author)jwystup2010-02-24

 Hey, I added a note in the picture so people do not get confuse.


I am happy that you where able to find the problem on your own! Great job!

Solarbotics (author)2010-02-22

kal00: Adding a second capacitor doesn't take over charging while the first is discharging. The solar cell simply keeps adding its power output to the power being dumped by the MSE circuit.

What it does do is let you store more power before activation, for a more impressive power burst!

TheSmartLemon (author)2010-01-28

BTW if you weigh the driver down it wont tip unless it has tremendous speed
probably about 0.5 kg would do it

 Yes but remember that the pager motor has no torque, so 500gr is WAY to heavy and the pager motor will not be able to roll the robot around.

You really need to make that robot light and have that third top wheel.

oh well mine has about 2 kg torque so it can withstand it

it looks exactly the same a well(the motor)

santy22 (author)2009-11-25

 Just here to say remember THIS

JavaNut13 (author)santy222010-01-05

Who doesn't!!!

thedogsaysocho (author)2009-11-17

total cost?

Jodex (author)thedogsaysocho2009-11-20

Not much if you just take the components out of old broken devices. ; D

robomaniac (author)Jodex2009-11-20


robomaniac (author)robomaniac2009-11-20

some parts can not be find in broken stuff...


if you search really long you might find all the stuff.

the plastic ball will be the hard part.  The 1381 is second, solar cell comes in third.

You could make a solarengine with a other type of circuit because the 1381 is hard to find, I never found one in more then 10 years.

good luck!

If you can't get a 1381, this should work ( I have not tried it yet )

step 2
this link

23$ and you will also need some paperclips, 3 cm of wires and the plastic sphere.

Then you have everything to rock and roll!

lowercase (author)2009-11-29

Is it tightly sealed??

PLEASE, PLEASE put in in the water, I want to see a video!


About This Instructable




More by Solarbotics:The Ardweeny: the little friend of the Arduino (and how to beef it up)Solar Powered Battle Symet - BEAM StyleSolar Powered Miniball Wannabe
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