Welcome! We've been eagerly anticipating your visit.
For the next couple hours we're going to dabble in electronics.
Understanding electronics is pretty crucial in Medical Physics, which is what our department concentrates on at Ryerson. As researchers, we're always building and improving amazing technology for diagnostic imaging and clinical treatment of diseases like cancer. With a foundation in simple circuits, it becomes much easier to understand things like ultrasound, computed tomography x-ray scans, and MRI (magnetic resonance imaging) systems, and to even design and build our own equipment.
But it doesn't all need to be about research and the serious business of Medical Physics. Electronics can also be really creative and fun.
Today we're going to build some circuits that make light and noise... circuits that, in a way, are a little bit artistic and a little bit scientific.
- Learn a few basics about electronic components.
- Learn a bit about reading circuit "schematics."
- Have some fun, build some devices!
- Identify a bit of the physics... there's physics in the circuits themselves, and in what you can do with them.
- Check out a bit about where the electronics and art meet.
Here's a taste of the art stuff:
or the very cool Arduino Phone (!!!).
or check out http://www.graffitiresearchlab.com/blog/projects/led-throwies/ (!!!)
Suffice to say, when you know a bit about electronics it opens up whole new creative worlds!
A secondary goal:
There's a reason this stuff is hands-on. We want to show you that it's not so hard to get your hands dirty and do some creative stuff that might, to many people, seem "too technical."
These days information is more readily available than ever (check out blog.makezine.com or www.instructables.com), and access to amazing equipment and tools has never been easier. The most expensive part of today's work is the breadboard we'll use, and they only cost $5.
Ryerson Physics put on our own light show recently for Nuit Blanche Toronto. Here's a peek at our submission from 2013:
Cool, eh? All it took was a few bucks, and some willingness to study a bit and experiment.
So, let's dive in.
The crucial fundamentals
There are a few things we'll need to know, at least a bit:
- Voltage Sources
Breadboards are super-important for "prototyping" circuits. They're great because mistakes are easy to correct.
A breadboard is shown in the image to the right. The holes in the breadboard's surface are connected inside as shown in green. Note, the red and blue "rails" down the sides of the breadboard provide voltage (+9V red, 0V blue) which will power our circuit.
When you poke a component into a hole, the component becomes connected to every other hole in the row.
To speed things up, we've also preassembled a little bit of the circuit for you (we connected a couple super-awesome special chips, aka integrated circuits, and we added a 9V battery connector). See image below.
Also note that the horizontal rows are labeled a-e and f-j while the vertical rows are labeled 1-30. This will come in handy.
Voltage sources provide energy within a circuit. Batteries are a prime example.
A battery contains potential energy (in the form of chemical compounds). When given the opportunity, batteries provide a steady (we hope) current that flows from the positive terminal (high potential energy) to the negative terminal (low potential energy).
To eventually be able to read schematics you need to know the symbols for components, so:
Think of a battery or any other voltage supply like water reservoir. Open a dam and the water naturally wants to flow downhill. Along the way it can do work, like turning turbines or pushing boats. Similarly, batteries generate a current that does useful stuff ("work") within the electronic circuit.
Other examples of voltage sources are things like wall outlets (120 volt "alternating current," which can kill you, so always be careful), or solar cells (providing "direct current", usually at low voltages unless you connect a bunch in series).
There are a few very basic components that make up almost any circuit:
Conductors are, obviously, the wires that link things like batteries and resistors and let current flow. In schematics, these are just the lines connecting other components.
These restrict the flow of current. Electrons basically bump into the atoms in a resistor and loose some of their energy (which gets turned into heat).
You also need to know that resistors are colour-coded. They usually have 4 coloured bands. We'll sort that out as we go so that you'll use the correct resistors where they're supposed to go.
Capacitors are components that store charge up.
Most capacitors are parallel plates, separated by a little space or special material that increases their performance.
When you apply a voltage to a capacitor, either positive or negative charge builds on one of the plates and the opposite charge builds up on the other plate. After a bit, there's so much charge built up that the current stops. Then if you reverse the voltage, the capacitor discharges and reverses its charge state.
As a result, AC current basically flows through a capacitor as if it's not there. DC current on the other hand sees capacitors as a break in the circuit, and current stops.
- Some other stuff you'll encounter
Operational amplifiers, or "op-amps"...
Piezoelectric transducers (we'll use them as speakers, but they can also be sensors)...
So you've seen a bunch of symbols we'll encounter, and pictures of actual components like resistors and capacitors.
Physicists and electrical engineers diagram their designs in "schematic" representations of a circuit. They can look messy, and they take some time to get used to, but with a little practice they get easier and easier to read.
Here's an example (a pretty complicated one if you're new to this stuff, but don't sweat it... we'll start simple and build up to the more complicated stuff.)
In fact, once you've had a little practice, reading schematics is no different than assembling a jigsaw puzzle. You're just putting the pieces in the right places based on the instructions the diagram provides.
Anyway, let's move it along and get building!