Systems 3/4 - Electronics 2

Analogue signal

1. Description

2. Example component

3. Graph

1. A signal that can have much variation between a minimum and maximum value.

2. Potentiometer

Digital

1. Description

2. Example component

3. Graph

1. A signal that can is either on or off (1 or 0)

2. Switch

Anode and Cathode

1. Description (which is which)

2. Diode diagram (or most components)

3. Battery diagram

1. Cathode is the positive (Think Cathode has a t in it, +, positive). Anode is opposite.

   (Battery has conventional current leaving Cathode)

Switch poles and throws

1. Description

2. Diagram symbol (single and double of both poles and throws - 4 diagrams)

Poles: Number of moving "flaps".
Throws: Number of positions switch can make circuits
(You dont have to draw the arrow heads)

Semiconductor

1. Description

2. Example (2)

1. A material that is half way between a conductor and insulator, typically activating when current is added in various ways

2. Diode, transistor

Diode

1. Description

2. Diagram symbol

3. What a physical diode looks like (not LED)

1. A device that permits current to flow through it in only one direction.

Zener Diode

1. Description (forward/backward bias?)

2. Use case

3. Diagram symbol + (rare)breakdown graph

1. Works like a diode in normal forward configuration (bias), but in backwards bias allows a set amount of voltage to pass when inside a breakdown region (min and max current)

2. Clamping voltage in a power source

LED

1. What does it stand for?

2. Description

3. Is it polarised?

4. Diagram symbol

1. Light Emitting Diode

2. A semiconductor that emits light when current flows through it.

3. Yes. Connecting it backwards might break it.

Photo Diode

1. Description

2. Use case

3. Diagram symbol

1. Only allows current to pass in one direction AND if light is shining on it.

2. Light-controlled switch.

BJT Identification

1. What does it stand for?

2. Description/ use case

3. Diagram symbol (NPN and PNP)

1. A Bipolar Junction Transistor

2. A component that acts as an electrical switch or amplifier (increase of current)

PNP and NPN current directions

1. Which way does the voltage drop need to occur for PNP?

2. Which way does the voltage drop need to occur for NPN?

1. When there is a voltage drop (0.7v) from emitter to base, then a larger current can flow from emitter to collector

2. When there is a voltage drop (0.7v) from base to emitter, then a larger current can flow from collector to emitter

(rare + tough)
NPN BJT use case diagram

1. What happens to flow of electrons when there is low resistance in the LDR (darkness)?

1. Low resistance of LDR allows flow of electrons around outer trace, allowing current into the NPN (voltage drop), allowing an LED to turn on

(rare + tough)
PNP BJT use case diagram

1. What happens to flow of electrons when there is low resistance in the LDR (darkness)? How is this different from NPN?

2. What happens when there is high resistance in the LDR (brightness) instead?

1. Low resistance of LDR allows for flow of electrons around outer trace, but the PNP RELEASES current when active (reverse bias), so does not activate, so LED is not turned on.

2. The current would flow preferentially through the BJT from emitter to base, turning on the LED.

General battery card (FINISH)

Capacitors

1. Description

2. Use case

3. Diagram symbol

1. Component that has the ability to store and discharge electrical potential energy, similar to a battery but much faster

2. Smoothing rectified DC voltage, removing noise/ decoupling, timing circuits

(rare) Types of Capacitors
Provide for each numbered type the:

• Name

• Electrostatic or electrolytic

• Polarised?

• Typical capacity (roughly)

• Pros/Cons

1. Tantalum - electrostatic - non-polarised - Less than 1µF - tiny, medium density, $, flammable

2. Electrolytic (name and contents) - polarised - More than 1µF - large, high density,

3. Ceramic and polyester - electrostatic - Less than 1µF - small, low density, $

(rare)
Variable capacitor

1. Description

2. Use case

3. Diagram symbol

1. Capacitor where the capacitance is changed electrically or mechanically

2. Resonant circuits, such as radio tuners

Voltage divider

1. Description

2. Why do we prefer a voltage regulator?

3. Identification (diagram)

1. Two resistors in series, where the voltage drop across one can be used in parallel to provide that lower voltage

2. As the total voltage drops (eg. battery), so does the output voltage - not desirable

Voltage regulator

1. Description

2. Use case

3. (rare) Common name of one

1. A device that maintains a constant voltage level (voltage divider lowers in voltage as total voltage drops)

2. Computer power supply

3. LM7805 (05 is the output voltage)

(rare)
Inverter

A device that converts DC to AC.

Open/Closed loop systems

1. What is a closed - loop system?

2. Example of closed - loop

3. What is an open - loop system?

4. Example of open - loop

5. Example of a combined open and closed loop system

1. A system with an automatic feedback loop

2. Automatic temperature control

3. A system that does not influence it’s own actions

4. Toaster

5. Fridge (temp-control + door light)

Resistors

1. What does the coloured bar on the far right (by itself) refer to?

2. What does the bar next to that one refer to? (second from right)

3. What do all other bars refer to?

1. Tolerance (= percent given in data sheet)

2. Multiplier (= number zeroes)

3. Digits (= actual digits, left to right)

(rare) LCD

1. What does it stand for?

2. Description

3. What does it look like (Image)

1. Liquid Crystal Display

2. Thin electronic display to block light in a grid to display images (no emission of light)

(rare)
Input transducer

1. Description

2. Example

1. Component that takes variations in physical (mechanical) energy and converts it into an electrical signal that can be read

2. Microphone