Page 124 - Making things move_ DIY mechanisms for inventors, hobbyists, and artists

104 Making Things Move

important to know that work, energy, mechanical power, torque, rotational velocity,
and electrical power are all related to each other with simple mathematical relationships.
And you can use them to figure out how to make things move!

Powering Your Projects

Remember that energy can’t be created or destroyed; it just changes form.
Transduction is the conversion of one form of energy to another. It follows that
anything that converts energy from one form to another is called a transducer. For
example, a motor is a transducer that changes electrical energy into kinetic energy, or
motion. Light bulbs and light-emitting diodes (LEDs) are transducers that change
electric energy into light and heat. Our bodies are transducers that change chemical
energy into mechanical energy. Some of my students have created stationary bikes
that power televisions and rocking sculptures that generate electricity by turning a
motor. The number of ways you can convert one kind of energy to another is as
endless as your creativity.

Back in Chapter 1, I defined a mechanism as an assembly of moving parts. Now
you know that moving parts have kinetic energy. That energy needs to come from
somewhere, right? Luckily, there are many energy sources we can use to make things
move. Not all of them are practical for small-scale work, so we’ll focus on the ones
that are. The electricity we get from the wall socket comes from other sources like
burning coal (and possibly wind or hydropower) that are not directly useful to us.
But all we need to know at this point is that the wall socket provides a source of
AC power.

To determine your preferred power source for a given project, consider these
questions:

• Is your project actually mobile, like a robotic car? If it needs to be truly mobile,
you may choose batteries or another power supply small enough to lug
around.
• Will your project move but stay in one place, like a painting rotating on the
wall? If so, you can use a wall outlet, but you probably need to convert the AC
power to DC power. You can do this with AC adaptors like the ones found on
your cell phone or laptop computer chargers.