Roly Poly LED




About: ECE student at Carnegie Mellon University.
Roll a metal ball around a plastic container, make the electrical connections and watch as the LEDs light up in succession!! OoooOoo

Step 1: Get Parts!

When I came up with this project I was cleaning out my desk and found a little clear plastic container. I knew it could be of some use, so I thought a little bit and came up with this.

With a little creativity I'm sure you can substitute a lot of these parts for something similar.

You need:

2 AA Batteries
A holder for these batteries (see picture)
A small plastic container
A small steel ball or another ball that conducts electricity
12 LEDs
Aluminum Foil
Soldering Iron
Scotch Tape

Step 2: Burn Holes and Attach Battery

There should be 3 holes in the plastic, not 2 like the picture. I burned through the plastic using my soldering iron - a horrible idea, but there was nothing else around. it works.

Insert batteries into the battery pack. Tape it to the bottom of the plastic lid and loop the wires through the holes. The positive wire from the battery pack (usually red) should stay on the top side of the plastic, while the negative wire (usually black) should loop through the second hole back to the side with the battery.

Using a tape measure, make a small mark on the edge of the lid about every 2.25 cm (But it will depend on the circumference of your lid and how many LEDs you have. To figure out how often to make a mark, do the following:

Circumference of the lid / Number of LEDs

This is purely aesthetic; if you don't care about your LEDs being evenly spaced or just want to eyeball it, the device will still work.

Step 3: Putting the Foil On

Measure and cut out aluminum foil to shape the inner portion of the inside of the plastic lid. This will make the connection between the steel ball and the battery to light up the LEDs! (You can tape this foil down with scotch tape so it doesn't rise up)

Then cut out a ring of foil and place it on the bottom. Take small pieces of tape and tape the foil on the bottom down every inch or so.

When you are done with that, tape the exposed part of the positive lead under the circle of foil and make sure it is making a good connection. You might want to also tape it down.
Then do the same thing with the negative lead on the outer side.

Step 4: Inserting the LEDs

Usually, LEDs have two leads with one longer than the other. The longer lead is the positive (anode) lead. The negative lead will be making a permanent connection with the ring of foil on the outside. The inner lead should be trimmed so that a little bit is sticking out into the center of the lid - this is so that when the metal ball passes the LED it will brush up against this lead and make the electrical connection between the LED and the positive terminal of the battery, connected to the foil.

Insert the LEDs into the melted-out semi-circles. twist the negative lead so that it reaches down to the bottom, and insert it under the foil. Tape it to secure the connection.

Clip the positive lead and hang it over the edge so it is slightly intruding into the inside of the lid, but not so much that it will stop the steel ball from continuing to roll.

Step 5: Finish!

Take the steel ball and roll it around inside the lid - hopefully the LEDs are making good connections and light up!

If no LEDs are lighting up, you first should check that both your battery leads are making good connections. If only certain LEDs aren't lighting up, check those individual connections. And make sure they are inserted in the right way!

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    27 Discussions


    11 years ago on Introduction

    With a little imagination, this could be be used a lot of places. How about leveling a table.


    12 years ago on Introduction

    That's great! I can think of a perfect application without changing anything: Teaching This is so easy and fun, a bunch of elementary school kids would love it! And they would learn about electricity, physics, and recycling without any boring textbooks! You're the best, Kyri!!!


    12 years ago on Introduction

    hehe, try attaching it to the rims of your car : )


    12 years ago on Introduction

    wow i can all most tell how to make this by look at the 1st pic very good


    12 years ago on Introduction

    I'm trying to think of a practical application for this. None come to mind, but it's really cool, anyway. Instead of capacitors, what if you used James' idea of aluminum foil, but put a coating so that the resistance of the foil changed from the center to the edge. That way, when the ball was right by the LED, it would get full power and be bright, but as it rolled away, there would be less power and the LED would gradually dim.

    1 reply

    Practical application = a bomb detonator
    "Don't pick that up!"
    "Why not..." BOOOM!!!

    Not that I am saying anyone should do it just letting you know. You could also use it as an alarm with modifications. By the way great instructable, what about high powered LEDs?


    Reply 12 years ago on Introduction

    Oh, I guess I meant, I think adding a capacitor is a super idea and 2)Kyri-how did you come up with this? Anyhoo . . .

    lol. To add capacitors you need a more powerful battery so it will charge faster, otherwise you wouldnt get much effect. You could also just widen the contacts on the LEDs with aluminum foil tabs.


    12 years ago on Introduction

    You know with a little more development you could use this as a tool for say something like a drill. It could indicate if you need to raise the bit or lower it when drilling horizontally. Or in a drill press to obtain a plumb setup.


    12 years ago on Introduction

    Nice Instructable! This also could be transformed into a super-duper tilt sensor!