1. Simple Output Devices TASK 1.Collect a set of Output Device cards. 2.Match each symbol to the correct name, energy change and type (digital or analogue). 3.Get it checked. 4.Complete the following table with the correct information: SymbolName Energy Change Device Type

2. SymbolNameEnergy ChangeDevice Type M bulbelectrical lightanalogue motorelectrical kineticanalogue buzzerelectrical sounddigital solenoidelectrical kineticdigital

3. SymbolNameEnergy ChangeDevice Type loudspeaker electrical soundanalogue relayelectrical kineticdigital

4. Relay Switch Relay A relay is a switch controlled by an electromagnet. A coil of wire: carrying a current = magnet with no current = non magnet Symbol:

5. Relay M 230 V a.c. Example of Relay Use A high voltage mains motor is switched on when switch S is closed. The small current in the 9V circuit makes the electromagnet become magnetic. This closes the switch and starts the motor. 9 V S

6. Reed Relay The reed relay uses a permanent magnet to open or close a switch. This type of relay is used in burglar alarm systems to detect when a door is opened.

7. :. :. to alarm S magnet Experiment When the door is closed the magnet is close to the reed relay and switch S is open. When the door is opened, the magnet moves away from the relay, causing switch S to close setting off the alarm.

8. Solenoid A solenoid is a coil of wire surrounding a metal rod. It is an electromagnetic device that moves a metal rod backwards and forwards. Examples of Solenoid Use car central locking safe locks steering on radio controlled cars railway points

12. Light Emitting Diode (LED) LED Symbol: Energy Change:electricallight Type:digital output device (only ON or OFF).

13. Wiring up an LED An LED only conducts when it is connected the proper way around in a circuit. LED lights (FORWARD BIAS) LED does not light (REVERSED BIAS) electrons flow into point of triangle to light LED resistor in series An LED is damaged if too large a current passes through. A series resistor limits the size of the current, protecting the LED from damage. ***

14. Q1.(a)Which LED’s in the following circuits will light? R LED 1 R LED 2 R LED 3 R LED 4 (b)What is the purpose of the resistor R in the above circuits? (c)When an LED lights it is said to be biased. LED’s are wired this way. (d)When an LED does not light it is biased. forward reverse protect the LED from damage 1 and 3

15. Calculating Size of Resistor The resistor and LED are in series. So the voltage across the resistor and the voltage across the LED must add up to give the supply voltage. V R + V LED = V SUPPLY VSVS 0 V VRVR V LED ** not on data sheet **

16. x ÷ Example 1 An LED can withstand a maximum current of 20 mA at 2 volts. Calculate the minimum value of resistor required when the LED is connected to a 5 V supply. V IR

17. Example 2 An LED can take a maximum current of 18 mA at 2.2 V. Calculate the minimum value of resistor required to protect the LED when it is connected to a 6V supply.

18. Q1.The maximum voltage allowed across an LED is 2.3 V and the current through it must not exceed 10 mA. The LED is connected to a 5 V supply. Calculate the value of the resistor R connected in series with the LED. 270 Ω Q2.An LED takes 10 mA and 1.5 V to work properly. What value of series resistor is required if a 6 V battery is used. 450 Ω Q3.An LED and resistor are connected in series to a 9 V supply. The maximum voltage across the LED is 1.8 V and the current through the LED must not exceed 12 mA. Calculate the value of resistor required to protect the LED. 600 Ω

19. d g 7 Segment Display 7 rectangular LED’s are arranged as follows to give a 7-segment display. a b e c f The number 3 is displayed by lighting segments a, b, c, d and g Energy Change:electricallight Type:digital output device (segment ON or OFF).

20. Experiment 1 – Making Numbers Using a 7-segment display, display each number from 0 – 9 in turn completing the table below. DigitSegments Lit 0a b c d e f 1b c 2a b g e d 3a b c d g 4f g b c 5a f g c d 6a f e d c g 7a b c 8a b c d e f g 9a b c f g

21. Experiment 2 - Making Letters Make as many letters as you can on the 7-segment display completing the following table. LetterAppearanceSegments Used Aa b c e f g

22. Which Output Device? Selecting Output Devices Here is a list of output devices: buzzer, lamp, motor, relay, solenoid Which output device could be used to: (a)indicate required cooking time for oven is complete (b)move conveyor belt at supermarket (c)stop and start movement of conveyor belt at supermarket. buzzer motor relay

23. Q1.Give a suitable output device for each of the following situations: (a)an audible warning when an incubator become too hot or cold (b)a power on indicator for a stereo (c)switch on a high current circuit using a small current (d)indicator of which TV channel is selected (e)to push chosen sweets to hatch in a vending machine (f)run a conveyor belt around a bottling factory. buzzer LED relay solenoid 7-seg. motor

24. Binary Numbers Binary numbers consist of a series of 0’s and 1’s. Consider the binary number 1101. 1 1 0 1 means 1 lot of 8 means 1 lot of 4 means no lots of 2 means 1 lot of 1 So we have as a decimal number:8 + 4 + 0 + 1 = 13 8421 continue to increase (double) just in same way as we represent decimlas by H T U 7 8 9

25. ** You must know the binary for numbers from 0 to 9 ** 8421 DecimalBinary 00000 10001 20010 30011 40100 50101 60110 70111 81000 91001

26. Q1.Copy and complete the table of decimal and binary numbers: DecimalBinary 00102 01117 111115 1001018 1011123 Q2.What decimal number is represented by the binary number: (a)0100(b)1001 49

27. Relay