110.626 Electronic Tutorial Parts 1-3 Light Emitting Diode - Resistor - Diode - Transistor - Capacitor Contents - Notes on mounting the components - The Light Emitting Diode - The Resistor - The Diode - The Transistor - The Capacitor - Practical circuits - Parts list Please Note The OPITEC range of projects is not intended as play toys for young children.They are tea- ching aids for young people learning the skills of Craft, Design and Technolo- gy.These projects should only be undertaken and tested with the guidance of a fully qualified adult. The finished projects are not suitable to give to children under 3 years old. Some parts can be swallowed. Dan- ger of suffocation! E110626#1 1 !!!WARNING!!! Do not push the drawing pins into the board with your thumb or finger. Use a small pin hammer to drive them in. Notes on building the circuits Solder or clamp? The circuits are designed to be constructed on the base board. The choice is yours whether the components are held in clamps or soldered into position permanently. SOLDER: The parts can be soldered to drawing pins which are tapped in to the base. The heads should be lightly tinned before mounting any of the parts, so that a minimum of heat is necessary during further work. CLAMP: To clamp the parts into position, the springs can easily be mounted onto the base with the drawing pins. Then the springs only have to be bent back (see diagram). Base USING THE SPRINGS AS SWITCHES AND CONTACTS For a short contact bend For a long contact hook the springs together the springs together. Contact Switch 2 E110626#1 The LIght Emitting Diode The Light Emitting Diode (L.E.D.) is not a lamp or bulb. The light from a L.E.D. is from a small crystal electro- magnetic wave, which we can see. If you hold a L.E.D. up to a light source, you can see the crystal inside. Crystal The light from a L.E.D. is not as bright as that from a bulb. LEDs are used mainly as warning and control lights to display a particular function, e.g.in Hi-Fi units, cassette players, computers, digital watches and televisions etc. Nearly every place you see small lights in electrical items, they are normally LEDs. They are available in red, yellow, green and blue, plus many different shapes. The most common shape for a Light Emitting Diode (LED) is rounded. The advantages of LEDs over bulbs are their: - small power consumption - long life - vibration resistance - strength - their ability to fit in small places Like all electronic components the LED has an Electronic Symbol. Symbol The two arrows symbolise the light being given out NOTE: When you are using a LED, you should be aware of the following points: 1. The LED will only light if it is connected the correct way round. The polarity of the legs can usually be iden- tified as shown in the diagram. A denotes the anode and C the cathode connection. The LED is too small to print on, so the Anode (+) leg is usually longer the than the Cathode (-). Symbol A Anode (+) connetion (plus) A C C Cathode (-) connection (minus) 2. The LED should not be subjected to more than 1.6 volts otherwise it can burn out. However most circuits need a greater supply than 1.6 volts and therefore you must add a resistor connected in series to ensure that the current flowing to the LED is kept under control. The most important component here is the RESISTOR Differing power sources need different values of resistor. Here is a list of the most common power sources and the necessary resistor values. 130 Ohm 4,5 Volt 180 Ohm 6 Volt 390 Ohm 9 Volt 510 Ohm 12 Volt 1,2 K Ohm 24 Volt E110626#1 3 The resistor The resistor is an electronic component which restricts the current flow in a circuit.The most common resistors are made from carbon on a ceramic core. (carbon is a poor conductor). At either end of the resistor is a wire for connection to other components. Coloured rings show the value of the resistor. Resistance is measured in OHMs. These coloured rings are a code to show the differing values of each resistor and whether it will let a lot or litt- le current flow through. So a resistor with a value of 1.8 K Ohm (1800 Ohms) will let less current pass as one of 130 Ohms. The following table shows the different Ohm values of resistors. Ringcolour 1st. ring 2nd. ring 3rd. ring/ 4th. ring/ multiplier tolerance black 0 0 1 brown 1 1 10 1% red 2 2 100 2% orange 3 3 1000 - yellow 4 4 10000 - green 5 5 100000 - blue 6 6 1000000 - violet 7 7 - grey 8 8 - white 9 9 - gold 0,1 5% silver 0,01 10% no ring 20% resisistor symbols sample: 130 Ω with 5% tolerance fixed value adjustable resist (potentiometer) brown orange brown gold 1 3 0 5% 4 E110626#1 EXPERIMENTS USING A LIGHT EMITTING DIODE AND A RESISTOR + circuit diagram A C 130Ω 130Ω - drawing pin Experiment 1: Tap the drawing pins into the base to make the pattern as shown. Use the chart to identify a resistor with 130 Ohm resistance. Connect the battery as shown in the diagram. The LED lights BRIGHTLY !. circuit diagram + A 1,8kΩ C 1,8kΩ - Experiment 2: Exchange the 130 Ohm resistor for a 1.8 K resistor The LED now lights..................................... Why? Because the resistor is ........................................................... circuit diagram + C 1,8kΩ A 1,8kΩ - Experiment 3: Remove the LED and turn it around and place it back in the circuit. Does the LED light...................... Why? You can find the answer by making further experiments using DIODES. E110626#1 5 The DIODE The diode is also a widely used component in electronics. It is what is generally known as a semi-conductor device. Taking copper as a good conductor and plastic as a poor conductor, a diode is made from silicon, a material with properties in between these two. The silcon diode has a special character. The semi-conductor diode lets the current flow in one direction only and acts like the valve on a bicycle tyre which will let air in but not out. This means it has the flow direction and reverse closed direction. Due to this property diodes are used to convert alternating current to direct current by removing half of the in- coming wave. The diode can also be used to control the direction of current around a circuit. The diode has also an electronic symbol. This helps us to see how it functions. Looking at the diagram you must pay attention to the connections marked A = Anode (+) and C= Cathode (-). A C As diodes are also too small to print on, so the Cathode (-) connection is shown as a band. C A diode will only work when the correct connections are made to the battery. flow direction Anode + Cathode - If a diode is reversed the current cannot flow. closed direction Anode - Cathode + EXPERIMENTS USING A DIODE circuit diagram + A 130Ω C 130Ω - A C Experiment 1: Make up the circuit as shown in the diagram. Be careful to connect the diode with the cathode(-) ring towards the negative side of the battery. The LED will light up! 6 E110626#1 circuit diagram + A 130Ω C 130Ω - C A Experiment 2: Unsolder the LED and change it around, reconnect. The LED does................................ Why? The diode is.................................connected If the circuit is to work ...............................must be the correct way around. Even LEDS must be correctly connected, as they have a flow and a closed direction.! ! ! EXAMPLES OF USING A DIODE circuit diagram + T1 T2 T1 T2 A A C 130Ω C 130Ω - Experiment 1: Make up the circuit as shown in diagram 1. Imagine that you are making a intercom system such as in a wai- ting room. By pressing switch 1 LED 1 will light and by pressing switch 2 LED 2 will light. Now we can change the circuit so that by using switch 1 one LED can be lit and by using switch 2 both LEDs will light. + T2 Fix a wire to the two T1 switches A A Experiment 2: Now press switch 1 and then switch 2 ! What happens ? In both cases the two LEDs light. However we want the left hand LED to light by pressing switch 1. This means that current must NOT flow to the right hand LED. But by pressing switch 2 we want current to flow to both LEDs. How can we alter the circuit? Do you remember the characteristics of a diode? Use a diode to solve the problem. The following circuit diagram shows you how to build the correct circuit. If you are still stuck, look at the diagram on the front cover. T1 T2 circuit diagram 130Ω E110626#1 7 BUILDING SOME PRACTICAL DIODE CIRCUITS The following circuit diagrams show you how to make some practical projects using diodes. Use a wooden base to mount the components and build the circuit into a box. If you wish you can use an old soap holder or plastic box as a container for your circuit. Project 1: A POLARITY TESTER circuit diagram + 130Ω C A 130Ω - A C red black red black Function: if the red crocodile lead is connected to the plus pole and the black lead is touched on to the negative pole, the +LED will light. If you change the leads over, the - LED will light.