Electricity

Why do I need to learn this?

Robots run on electricity. Your mini-bot is small, light, and uses penlight batteries - it's safe; however the FIRST robots you will build later this year weigh up to a couple of hundred pounds, use powerful motors, solenoids, and pneumatics, and run on batteries with enough energy to seriously hurt you. So you need to learn the basics of electricity and how to control it because:

1. It's interesting and fun
2. Ignorance is not bliss: so much of our modern world depends on electricity, everyone should have a basic understanding of what it is and how it works
3. Safety: everyone who works on or with the FIRST robot must understand how to stay safe and keep the robot from hurting itself or others.

Objectives

By the end of the lesson you should understand:

• Electricity
  • ​What is electricity
  • Units of measure: Volts, Amperes, Watts, Joules, Ah, KWh
  • The ​water analogy
  • Who's who (literally): ​Volta, ​Ampere, ​Watt, ​Joule, ​Ohm
• Batteries
  • What is a battery
  • ​Primary vs. secondary
    • FIRST bots use sealed ​lead-acid batteries (1800s technology!)
    • Mini-bots use primary alkaline batteries (developed 1899-1901)
  • Voltage:
    • Nominal voltage (alkaline=1v5/cell, SLA=2v15/cell)
    • ​Series connected cells multiply the voltage
    • Real world: discharge curve, temperature effects
    • Datasheets: ​alkaline ​SLA
  • Current:
    • ​Internal resistance
    • What are ​Cold Cranking Amps anyway?
  • Capacity:
    • Amp-hours
    • ​discharge rate matters!
    • ​ratings games)
  • ​specifications cheat sheet
  • Energy density
  • Self discharge
  • ​Using a multimeter to measure voltage and current
• Conductors/Circuits
  • What is a conductor
  • Using a multimeter to measure continuity
• What is a resistor
  • Units of measure: Ohms
  • Using a multimeter to measure resistance
  • The ​resistor color code
  • Series and parallel resistance
  • Power dissipation (or why you don't want to be a fuse)
• How electrical power and resistance are related: ​Ohms law
  • How to use a resistor to limit current (e.g. series resistor for LED or pull-up/down for an input)
  • How to use a resistor to measure current and power (e.g. to monitor how hard a motor is working)
• What is a diode
  • anode, cathode: controlling the direction of current flow
  • Special diodes: light emitting diodes
  • Diode lasers

Experiments

Your kit includes a variety of electronic components that you can experiment with including connecting them to your Arduino computer. The kit also includes a solderless breadboard that lets you build electronic circuits quickly and easily without having to use a soldering iron. Please read the tutorial on how to ​use a breadboard and jumper wires to make circuits

Your kit also includes an Arduino protoshield: a circuit board with pass-through connectors that you can stack onto your Arduino computer to use it to power and control your electrical circuits. Please read the ​protoshield tutorial on how to use your protoshield and solderless breadboard to connect sensors and actuators to your Arduino computer.

• Connect jumper wires to +5v and Gnd connections and measure the voltage with your multimeter
• Connect +5v and Gnd through a 270-ohm series resistor and an LED to make it light up
• ​Blink an LED: connect a 270-ohm series resistor and an LED between an Arduino digital pin and Gnd and make it blink
• ​Multiple LEDs: connect a bunch of Arduino pins, resistors, and LEDs to make a festive light display
• Using a multimeter, measure the voltage across a series resistor in a circuit and calculate the current being used by the circuit.