Electronics for Artists
Class #1
#1
Class
basics of
of electricity,
electricity, tools,
tools, circuits
circuits
basics
Some basic vocabulary/concepts
Current - the flow of charged electrons
Conductor - a substace through which current flows
Voltage - force pushing current
Resistance - force trying to push back against current
Power - amount of work done
Think of a hose with water flowing through it. The water is analagous
to electricity and the hose is analagous to a conductor. The pressure
or force behind the water is analagous to voltage and the amount of
water flowing through is analagous to current. Now let’s say you
cram a sock into the hose, water will still get through but not as easily.
The sock is analagous to resistance. Power doesn’t quite fit into this
analogy but is like a measurement of how much water flowed and at
what pressure.
The same concepts only not so basic
Current:
1) Measured in amperes or “amps”, abbreviated as I (think I for “intensity”) and sometimes as
A (yes, this can be confusing).
2) In order for current to flow there must be an imbalance of charge between two points
(voltage).
3) Definition: the ampere is a constant current which, if maintained in two straight parallel
conductors of infinite length, of negligible circular cross section, and placed 1 metre apart in a
vacuum, would produce between these conductors a force equal to 2×10–7 newton per
metre of length. (I don’t know what this means but I can still use electricity to make cool
things)
Voltage:
1) Measured in Volts abbreviated as V(not confusing).
2) The difference in charge between two points. so a voltage does not exist in isolation.
3) We will be measuring voltage with respect to “ground” (more on that later).
Resistance:
1) Measured in Ohms and abbreviated as R (moderately confusing).
2) The degree to which an object opposes a current running though it (you have resistance).
3) The amount of resistance in an object depends on the strength of electron bonds in the
object.
Perhpas you noticed that the definitions of voltage, current and resistance refer to one another? This is the basis for:
Ohm’s Law
which states that the current passing through a conductor between two points is directly proportional to the potential
difference (i.e. voltage drop or voltage) across the two points, and inversely proportional to the resistance between
them.
Or stated in a way that actually makes some sense (at least to me):
V=IxR
or
I=V/R
or
R =V / I
V
IxR
The magic V I R-triangle can be used to calculate all
formulations of Ohm's Law.
Use a finger to hide the value to be calculated. The other
two values then show how to do the calculation.
Still more concepts in not so basic terms
Power:
1) Power is measured in Watts and is abbreviated W.
2) Power is the amount of work that is done.
3) W = I x V (watts equals amps times volts - nice and simple)
Ground:
In A.C. (alternating current - the type that comes out of the walls of our homes) terms ground
literally means the ground. The Earth. The power company uses the mass of dirt and rocks
and water and molten lava and minerals and oil and etc. that we Earthlings live on as a wire in
their circuits. The earth has a fairly consistent potential voltage against which other voltages
can be measured and is a pretty good conductor. In D.C. (direct current - the type that we’ll be
using from batteries) terms, ground is sometimes called “common” and can be thought of as a
zero voltage level against which other voltages can be measured. Think of ground (or
common) as electricity sea-level.
Some keys to fun successful electronics
projects:
Expect things to not work. Anticipate lots of (possibly frustrating)
troubleshooting.
Document your progress and process.
Help eachother, share things you discover.
The internet knows everything.
Circuit
1) A circuit is a collection of electronic gizmos which (hopefully) do
something interesting, fun, beautiful, useful, etc.
2) A working circuit must have a closed loop of current flow through a
load.
3) All circuits contain voltage, current and resistance.
4) A circuit with a break in it is called an open circuit and is really boring.
5) A circuit without enough resistance in its load is called a short circuit
and is a very bad thing.
Schematic
1) A schematic is a diagram which represents a circuit.
2) The way this abstracted diagram looks is usually not how the final
physical object looks.
Schematic symbols of some common “electronic gizmos” we’ll be using:
+
battery - where we’ll get our charge
ground - “zero” voltage, for our purposes the negative terminal of a battery
capacitor - stores a bit of electric charge
+
polarized capacitor - same but current only flows one way
resistor - adds resistance to a circuit
switch - allows current to flow or not flow between two points
diode - we’ll use light emiting diodes (LEDs) for some experiments - current will
only flow in one direction through these
transistors (NPN and PNP) - amplify current
amplifier - increases power flowing through it, really represents a circuit of several
of the above typically in a tiny package (for our purposes anyway)
Series Circuit
1) Components are connected end to end
2) There is a single path for all electrons to follow
3) Total resistance of a series circuit is the sum of individual resistances
4) Total voltage is equal to the sum of individual voltage drops
R1
9V
R1 10 kOhm
R2 1 kOhm
R3 500 Ohm
R2
R3
Rt = R1 + R2 + R3
Rt = 10,000+1,000+500
Rt = 11,500 ohm
Rt = 11.5 kOhm
Parallel Circuit
1) The same voltage exists across each branch and is equal to source voltage
2) The current through each branch is inversely proportional to the resistance of
that brance (lazy electrons take the easy route)
3) Total resistance of a parallel circuit is less than the sum of individual resistances
(more paths to travel)
4) Total current is equal to the sum of individual branch currents
R1 10 kOhm
R2 1 kOhm
R3 500 Ohm
9V
R1
R2
R3
1
Rt
1
1
= 10,000 + 1000 +
1
500
= 0.0001 + 0.001 + 0.002
= 0.0031
1 = 1 + 1 +1
Rt R1 R2 R3
Rt
= 322.6 Ohm
Multimeter
1) A device used to measure current,
voltage, resistance and continuity.
2) Allows us to “see” what the electrons are doing in our circuits
3) Measures current in series with a
circuit
4) Measures voltage in parallel with
a circuit
5) Numbers 3 & 4 are very important
points to remember to accurately
use a multi meter
Battery
1) Converts chemical energy into electrical energy
2) Batteries are either primary (non-rechargeable)
or secondary (rechargeable)
3) Rated in “amp hours”
4) Connected in series voltage is increased
5) Connected in parallel current is increased
Solar Cell
1) Converts solar energy into electrical energy
2) Also called photovoltaic
3) Rated by maximum amps and volts they can
output in full sun (less sun = less output)
4) Connected in series voltage is increased
5) Connected in parallel current is increased
Breadboard
1) Temporary assembly (prototyping)
board.
2) Conductive paths hidden below
sockets.
3) Sockets contain metal sleves which
connect components to paths.
4) Columns on outside connect while
rows on inside connect. Down the
center rows are split into two (see
image at right).
Wire
1) Provides low resistance path for current
2) Protected by insulated coating
3) Smaller wire handles less current before it melts
4) Diamater is measured in gauges. Large wire has a
smaller gauge, small wire has larger gauge (confusing).
5) We’ll be using 22 gauge solid wire which is rated for
about 2 amps.
6) Stranded wire generally handles more current and is
better for permanent circuits.
Resistor
1) Conductive material which impedes
current flow
2) Converts electrical energy into heat
3) Typical power rating of 1/4 to 2 watts
4) Uses color bands to identify resistance value (sucks if you’re color blind)
LED
1) Stands for light emitting diode
2) Converts electrical energy into light
3) Current flows from anode (longer leg)
to cathode (shorter leg)
4) Requires nominal 0.6V to conduct
Switch
1) Mechanical device which
starts, stops or redirects current flow
2) Characterized by number of
poles (parallel connections)
and number of throws
(possible paths for current to
take).
Alligator clips
1) Just a wire with little hands
2) Makes it easy to connect parts
into a breadboard circuit when they
won’t fit in the sockets
Lab One
- Series circuit using 1k resistors
- Measure current and voltage drops.
- Switch to 100k resistors. Does current change? Do voltage drops
change?
R1
9V
R2
R3
Lab two
- Parallel circuit using 1k resistors
- Measure voltage drop
- Measure current through each leg
- Measure total current
- Switch to 100k resistors. Do currents change? Does voltage drop
change?
9V
R1
R2
R3
Lab three
- LED circuit with switch
9V
340 R