Page 191 - 15 Dangerously Mad Projects for the Evil Genius

168 15 Dangerously Mad Projects for the Evil Genius

Figure 13-14 Testing with the Serial Monitor

You will then see a stream of numbers. The first Once you have the hang of it, you can try
number of each row is the position of the object (if levitating various kinds of object. For now, we will
any) that is being levitated, while the second start with an easy-to-make and inherently stable
number is the velocity—a positive number if the object based on a very small plastic bottle that
object is moving down and a negative number if it used to contain a health drink. The magnet is glued
is moving up. to the inside of the bottle lid, which is then
We do not have any object being levitated, so screwed back onto the bottle (Figure 13-15).
the position should read a high value, probably Before gluing the magnet onto the lid, we need
around 600. The velocity should be around 0, but to find the right orientation for it. The best way to
may jitter up and down a bit. We can test that the do this is to attach the power supply and wave a
transistor and LED are working okay by putting an
object (say a pencil or your hand) in between
them. This should decrease the “position” down to
0. You can also try moving the object up and down
past the sensor and see the velocity go positive and
negative as you move in different directions.

Step 9. Make Something to Levitate

The key to making an impressive distance between
the electromagnet and the object being levitated is
to put a strong permanent magnet at the top of the
object being levitated. We use a neodymium, a
rare-earth magnet. Despite their exotic-sounding
name, these are easily obtainable from eBay or a
hobby shop.

We could just levitate a metallic object such as a
nut or bolt, but a magnet will produce much better
results.
Figure 13-15 Bottle for levitation