SAASTE Technology/Activities/Electronic Circuits

Electrical System Grade 9 Electronics You will need the following component / Parts Resistors (all ¼ Watt 5% carbon) R1 - 680 Ohm R2 - 4,7 K Ohm R3 - 2,7 M Ohm (for activity 4) Semiconductor Q1 - BC337 (or equivalent) LED 1- 5mm LED 2 - 5mm infra red detector LED (for activity 4) A Resistor Colour Code Chart is available on the last page of this document. Connect / build the circuit shown in the diagram below: Note: The fly lead is simply a short length (approx. 10cm) of conductive wire (with both ends stripped of insulation) Activity 1: Attach the loose end of the fly lead to the negative (-) side of the battery and observe the output. Now remove the fly lead and attach to the positive (+) side of the output and observe the output. Activity 2: Disconnect the fly lead from the battery. Touch the end of the fly lead with your bare fingers. What do you observe? ........................................................................................................... ............................................................................................................ Activity 3: Connect another fly lead as shown in the circuit diagram below: Image:SA_NC_Saaste_Activities_3.png Insert both fly leads into a beaker containing water and observe the output. Activity 4: Use your original circuit and extend it by connecting LED 2 and R3 as shown in the circuit diagram below: LED 2 - 5mm. infra red detector LED R 3 - 2,7 MΩ Use any remote control (from a TV, Hi-Fi etc.). Bring it close to LED 2. Press any button on the remote control and observe the output. Note: An LED is a transducer: it converts energy from one form to another Component data: R1 - Blue, grey, brown, gold R2 - Yellow, violet, red, gold R3 - Red, violet, green, gold Note: 5%(gold), 10%(silver) or 20%(no 4th band) resistors may be used The colours for the 4, 7 KΩ resistor was worked out like this: Each number of the value of the resistor correspond to the three bands on the one end of the resistor. 4 in the first band = yellow 7 in the second band = violet K in the third band would be orange. Because there is a decimal place (comma) between the 4 & 7, we move one decimal place and now have 2 zeros which correspond to red. Try working out the colours for the following resistors: 47 KΩ, 50Ω, 330Ω , 100Ω , 560Ω , 390Ω. Semiconductors: Transistor Q1: BC 337: B-Base; C-Collector; E-Emitter Glossary= Resistor: An electronic component which slows or reduces the current and/or creates a voltage drop L.E.D. (Light Emitting Diode): A special diode which emits light when a current flows through it. Transistor: An electronic component which may be used as a switch or as an amplifier. They are broadly divided into PNP and NPN (the BC 337 used above is an NPN transistor) Infra-red: A narrow band of the light spectrum invisible to the naked eye. Anode: Positive Cathode: Negative Author: Ricardo Miller Contributions by Osman Sadeck Editor: Osman Sadeck