Sheila Porter Intel Ireland PowerPoint Presentation III Electronic Engineering l & ll Sheila Porter Intel Ireland

Electronic Engineering Session 4: Electronic Engineering I Students explore simple circuitry with bulbs, batteries, wires and breadboards Session 5: Electronic Engineering II Students use switches, LEDs and motors and investigate their application in the world around them Cordless Telephone

Session 4: Electronic Engineering I Key Concepts in Electricity 1. A complete circuit is needed for an electric current to flow. 2. A resistor will reduce the flow of current in a circuit. 3. The voltage of a battery or power pack is a measure of the 'push' that can make a current flow; the larger the voltage the larger the current for a given resistance. 4. Current is not used up when it flows through a circuit. 5. Not all electrical component obey Ohm's law, e.g. silicon chips, capacitors, light-emitting diodes (LEDs). 6. Circuits inside silicon chips can be turned on or off by changing the voltage they sense (rather than current).

Check Your Understanding Q.1 The diagram shows a battery and lamps connected to some wires. Why won’t the bulbs light? What would you do to make the circuit work properly? A.1 Circuit not complete Link wire and bulb

Q.2 We measure the amount of current flowing through a circuit in amps (A). Suppose the circuit is made to work properly so that both bulbs light. Also suppose we measured the current flowing through the wire at P as one amp (1 A). What would you predict the size of the current to be at point Q? What would you predict the size of the current to be at point R? A.2 (i) 1 A at Q (ii) 1 A at R Current is not used up in a circuit

Q. 3 Assume you had built the circuit so that both bulbs were glowing Q.3 Assume you had built the circuit so that both bulbs were glowing. What do you think would happen if you connected a wire from P to Q? A.3 The bulb would go out. The wire from P to Q would have a much lower resistance than the bulb, so almost all the current would go through the wire and not the bulb. The other bulb would glow more brightly.

Q. 4 Imagine the circuit was working properly, with both lamps glowing Q.4 Imagine the circuit was working properly, with both lamps glowing. Now imagine you replaced the 9 V battery by a 90 V battery. Write down what you think would happen, and why it would happen. 90 V Battery A.4 The 90 V battery would drive a much greater current through the circuit (about 10 times as much). It is likely that so much current would ‘burn out’ the filaments of the bulbs, i.e., they would glow very brightly for a brief moment and then stop working.

Connections on a Breadboard Horizontal row No connection Vertical row One or more horizontal rows of holes at the top. All these holes are connected together by a metal strip running underneath. One or more horizontal rows of holes at the bottom. These holes are also connected together. Two sets of holes in rows of five holes each, separated by a gap. These holes are connected vertically only. So, for example, two holes side-by-side are NOT connected. There is no connection across the gap.

Electrical Components

Building Simple Circuits Supplies Breadboard Battery Electrical wire 2 lamps 2 LEDs Procedure 1 Build the circuit shown in the photo to make two lamps light. Session 4, Activity A

LEDs – Light-Emitting Diodes Special type of diode which gives out light when a small current flows through it (forward bias) Flat Lens REMEMBER The cathode must be connected to the – terminal of the battery

LEDs – Light-Emitting Diodes 6 V 330  LEDs usually require a voltage of about 2 V to light Anything higher and they will ‘burn out’ 6 V330  Ordinary LEDs are used with a protective resistor in series with them The LEDs in our investigations have built-in resistors for convenience

LEDs – Light-Emitting Diodes Procedure 2 Identify anode and cathode on LED Remove bottom lamp from breadboard Insert LED and note whether it lights Turn the LED around and note whether it lights Replace both lamps with LEDs Connected to –ve terminal of battery Connected to the +ve terminal of battery REMEMBER The cathode must be connected to the – terminal of the battery Session 4, Activity A

Uses of LEDs Digital clocks Torch DVD player Lights at the top of the millennium spire (Dublin monument –height 120 m) Digital clocks Torch Traffic lights Pocket lens with light Iron

Using Simple Switches - Push Switch Supplies Circuit from previous investigation 1 push switch Procedure Try connecting the push switch as shown in the photo Does it matter which way round the switch is put into the circuit? (Try it.) Uses of push switch - camera, flashlight, etc. Session 4, Activity B

Using Simple Switches - Micro Switch Attach 3 leads as shown in the diagram Lever can be used to ‘magnify small movements Micro switch is very sensitive Can be used, e.g., to sound an alarm if attached to a window with even the slightest opening. Session 4, Activity B

Using Simple Switches - Micro Switch Supplies Circuit from previous investigation 1 micro switch Procedure Try connecting the micro switch as shown in the photo Complete the table below Wires used What happens to the lamps before the lever is pressed? What happens to the lamps after the lever is pressed? 1 and 2 1 and 3 2 and 3

Using Simple Switches - Micro Switch Wires used What happens to the lamps before the lever is pressed? What happens to the lamps after the lever is pressed? 1 and 2 Light off Light on 1 and 3 2 and 3 Pins 1 and 2 are known as ‘normally open (NO)’ Pins 1and 3 are known as ‘normally closed (NC)’

Using a ‘Silicon Chip’ 4093 silicon chip – Quad, 2-input NAND logic chip This chip contains four logic gates, each with two inputs It has 14 legs (pins) Students use pins 1, 2, 3, 7 and 14 Pins 1 and 2 are inputs, pin 3 is the output, of one gate The output depends on the inputs

How the Output Depends on the Inputs Wire connects pin 2 to – of battery Cathode connects to – of battery Anode of LED connects to pin 3 To + of Battery Wire connects pin 14 to + of battery Wire connects pin 1 to + of battery Wire connects pin 7 to – of battery To – of battery Supplies Breadboard + Battery Electrical wire 4093 silicon chip LED Procedure Build the circuit shown in the photograph. Complete the table in the workbook. Input to pin ON - when connected to + of battery OFF- when connected to – of battery Session 4, Activity C

Input Pattern for the 4093 Pin 1 Pin 2 Pin 3 (output) OFF ON Input to pin ON when connected to + of battery OFF when connected to – of battery Pin 1 Pin 2 Pin 3 (output) OFF ON ON ON ON OFF Session 4, Activity D

Session 5: Electronic Engineering Il Reed Switches Two thin pieces of metal sealed in a vacuum in a glass tube When a magnet is brought near the two metal contacts they are brought together and connected

A Reed Switch Circuit Supplies Procedure As Session 4, Activity C Build the circuit shown in the diagram. Bring the magnet near to the reed switch and observe what happens. Swap the LED for a buzzer Session 5, Activity A

Making an LED Flash To do this you need to use a capacitor and a resistor Capacitors: Store charge and consist of two conducting surfaces separated by an insulator. When connected to a battery a capacitor charges up until it reaches the same voltage as the battery When a conductor, e.g., a bulb, is connected to the charged capacitor current will flow from one plate to the other The charging and discharging of a capacitor can be slowed down by placing a resistor in series with it in the circuit. -

Resistors Resistance of a circuit is how difficult it is to drive a current through it. The bigger the resistance the smaller the current that can flow for a given voltage across the circuit. Resistance is measured in ohms (Ω). When we want to reduce the current flowing in a circuit we insert a resistor. Some resistors are made of wire but most are made of carbon. The coloured bands tell us what the resistance of each resistor is.

Resistor Colour Codes Two series—4-band and 5-band Colour Value Black 4- band code Bands 1 and 2 = first two digits of the value band 3 = the powers of 10. Band 4 = the quality of the resistor Gold band = 5% Silver band = 10%. Band 4 is separated from the other bands, to tell us at which end to start counting from Colour Value Black Brown Red Orange Yellow Green Blue Violet Grey White 1 2 3 4 5 6 7 8 9

Making an LED flash Supplies Procedure Breadboard Battery Capacitor Resistor 4093 silicon chip LED The – leg of the capacitor goes here Resistor 1 has one leg to pin 1, the other to pin 3 Resistor 2 has one leg to pin 3, the other to LED Note the link wire connecting pin 1 to pin 2 For 4093BE chip an extra resistor - 1k (BrBkR) - is needed between pin3 and LED Not required on 4093BP chip Procedure Build the circuit shown in the photograph Investigate how the flashing rate changes if you change the resistor Session 5, Activity B See website-’Electronic Fixes’

Controlling a Motor Chip 2003 Pin 8 must be connected to the negative of the battery Pin 9 must be connected to the positive of the battery

Controlling a Motor Supplies Procedure Components from previous session Electric motor 2003 chip Procedure Build circuit as in diagram Use pin 1 to turn the motor on and off Connect the motor between the +ve of the battery and pin 16 Do not allow the motor to run longer than 10 seconds at a time Session 5, Activity C

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