Circuits
What a circuit is and how it behaves, before touching an Arduino or a patch cable. A few hours here makes the Arduino and synthesis material much easier to follow.
The five-minute version
- Circuit: a complete loop. Current only flows if there is an unbroken path from the power source, through the parts, and back.
- Voltage: the electrical push between two points, measured in volts. A battery supplies it.
- Current: the flow of charge around the loop, measured in amps.
- Resistance: how much a part opposes current, measured in ohms. Ohm’s law ties the three together: voltage = current × resistance.
- Switch: a gap in the loop that can be closed. Open means no current. Closed means current can flow.
- +, − and GND: + is the higher-voltage side of a supply and − is the lower side. GND (ground) is the reference point that every other voltage is measured from. On the boards used here it is the same as the − side. Connecting + straight to GND with nothing in between is a short circuit.
- LEDs only work one way round, and always need a resistor in series to limit the current.
Suggested progression
- Build and break circuits. Interactive · Circuit Construction Kit: DC - University of Colorado’s PhET simulation. Add batteries, switches and bulbs, measure with a voltmeter and ammeter, and compare series with parallel. Runs in the browser, including on Chromebooks.
- Read the explanations. Read · What is Electricity? then Voltage, Current, Resistance, and Ohm’s Law - SparkFun.
- Read a diagram. Read · How to Read a Schematic - SparkFun.
- Build one for real. Read · How to Use a Breadboard - SparkFun. Then go to the Arduino Lab Guide.