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Electronics Intro

What should you know about Electronics to begin physical computing?

Keywords and important concepts are listed below.

This downloadable PowerPoint explains and illustrates these terms further. (best if downloaded and viewed as a ppt to see the animations)

Key Vocab & Concepts

Electricity - Flow of electrons from one area to another. We put something (a motor or bulb) in the way to make the electrons do some work for us as they pass by.
- Conductor- A material that lets electrons flow freely
- Insulator- A material that prevents electrons from flowing freely
Circuit- Closed circle of conductors that lets electrons circle from a higher-voltage area to a lower-voltage area. Parts of a circuit include:
- Source of power- Either a battery or a generator (possibly sent to an outlet) that provides electrical energy
  - - Current- The overall flow of electrons... how many pass in a certain amount of time. Current is measured in Amperes, or "Amps".
    - Voltage- The potential speed of the electrons... how much pressure they have to flow from the high-voltage area to the low-voltage area. Voltage is measured in Volts. An Arduino can be powered by 5-12V, and it can output either 3.3 or 5V.
    - AC- Alternating current comes from electromagnet generators and is what runs through our household outlets. Electrons flow back and forth, "alternating" 60 times per second.
    - DC- Direct current runs in one direction, from the negative side of a battery to the positive side.

- - Resistance- Pushing back against voltage... like how friction slows movement. Measured in Ohms.
    - Electrical resistors are put into circuits to slow the voltage and keep wires or components from overheating and breaking. Their resistance is shown by colored bands, using keys like the one shown here to identify the digits in the value of Ohms for the resistor.
    - Load- Anything powered by the current
    - Switch- Disconnects the circuit to "open" it, or reconnects it to "close" it and make it work again.
    - Diode- A 1-way connection in a circuit. An LED (Light-Emitting Diode) is an example that needs to be wired correctly, or it stops the electrical flow.
    - Short-circuit- If the circuit is supposed to go through a load, but the wires cross somewhere, a "short" is caused. Instead of pushing through the load, the current takes the path of least resistance and takes the shortcut back to the battery or outlet, so the load doesn't get powered.
    - Series circuit- Several loads connected in line, so that the current must pass through all of them in order to complete the circuit. If you disconnect one, all turn off. Each load divides up the total voltage, so two bulbs would shine half as bright as a single bulb.
    - Parallel circuit- Several loads are connected so that current can bypass any individual one. If you unscrew one, the others will stay on. Each load receives the full voltage, so two bulbs would be as bright as one.
  - Breadboard- Instead of permanently connecting wires when playing with new circuits, a breadboard lets you stick wires into shared channels that make temporary connections. Strips of metal underneath the breadboard's rows will connect wires below the surface, so understanding where the connections are is important.
    - Power rails- You will connect the power source's + and - electrodes to these rails to provide a power and a ground connection to an electronic component plugged anywhere on the entire + and - columns.
    - Terminal strips- Plug electrical components in to the numbered terminal strips, which will be connected to the + and - rails to bring the current into the electronic component and back out to the source
    - In the picture to the right, several different LEDs are shown. Notice the differences in how the two "legs" of the LEDs are plugged in. To work, the crooked leg of the LED needs to be connected to the + power rail, and the straight leg needs to be connected to the - power rail.
    - LEDs also need a resistor, or too much current will burn them out.
    - Only #5 & #6 are set up correctly to light the LEDs. The placement of the resistor before or after the LED does not matter.
      - #1 dead-ends, as both LED legs are on the same terminal strip.
      - #2 has no power, as its power rails are not connected to the battery.
      - #3 blew its LED because there was no resistor to reduce the voltage to a safe level.
      - #4 is wired backwards, connecting + to the straight leg of the diode instead of to the crooked leg.