After today's class you know hot to:
- Wire a potentiometer to Arduino
- Wire a resistive sensor to Arduino
- Wire a button or similar to Arduino. (Also sensors which act like buttons!)
- Adjust the analog voltage reference of the Arduino Board
- Use pull-up resistors.
What is resistance?
Resistance describes the ability of a substance to conduct electricity. Or better: it describes the the ability to NOT conduct - it describes the ability of a substance to resists against a current flowing.
- low resistance: charge (charged particles) can pass easily.
- high resistance: charge can pass less easy.
Examples:
- Thin wire - vs. Thick wire
- short wire vs. long wire
Similarity to garden hose:
- Short hose: lots of water
- Long hose: less water.
- Water: only approximately according to length twice the length causes half the water per minute.
- Current: perfectly according to length. Twice the wire length, half the current.
Interactive example: http://www.falstad.com/circuit/
Every conductor has its internal resistance. Higher resistance causes less current to flow. (in most cases) Lower resistance causes more current to flow. (in most cases)
Usual power supplies (Batteries, Wall plug adapters) are limited by their internal resistance. Lab power supplies are limited by an "intelligent" electronic which cares about the current.
What is a conductor, what is an isolator in sense of resistance?
- Conductors: low resistance - the lower the better for cables and circuit boards.
- Insulators: Ideally an infinite resistance. Reality: still very high resistance.
What does a switch mean in the sense of resistance?
- Switch opened: no current flow, resistance is near infinite.
- Switch closed: current can flow freely, resistance near zero.
Voltage Divider - Example in Ktechlab.
Time for Your Experiments!