ALTER 8+ 24 thrilling experiments 24 projets passionnants 24 boeiende projecten: 24 progetti entusiasmanti 24 fascynujące projekty
Imprint © 2019 Franzis Verlag GmbH, Richard-Reitzner-Allee 2, 85540 Haar bei München • www.franzis.de Author: Burkhard Kainka Idea/concept: Michael Büge, Burkhard Kainka Copy editor: Richard Korff Schmising Art & design cover: www.ideehochzwei.de Layout & composition: Nelli Ferderer • nelli@ferderer.de ISBN 978-3-645-15062-2 2019/01 Picture credits Drawings created with http://fritzing.org/ All rights reserved, including the rights for photomechanical reproduction and storage of electronic media.
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Children’s electronic calendar 2019 LEDs, transistors and the piezo transducer Dear children, Running up to Christmas there are 24 electronic projects waiting for you. The focus is on transistors, light emitting diodes, a light sensor and a small speaker. You can build completely different things with these components. There is much to see, to hear and to experiment! And if you want, you can find the information you need here to learn more about how everything works.
has a shorter wire (cathode = negative pole) and a longer wire (anode = positive pole). Inside you can see a slightly larger holder on the minus side, which carries the actual LED crystal. Once you have finished setting up, compare your construction with the assembly picture. It’s a good idea to get help from an adult who checks the first experiment again. In the following projects, only a few modifications are carried out, so that it becomes easier and easier.
2 Secret light signals Behind door number 2 you will find a pushbutton switch with four connection pins. Install it in the circuit so that it turns on the power as soon as you press the button. Two of the connections are connected inside. If you have installed the push button the wrong way around, the power will always be on. When the LED lights up as soon as you press the button, it is correctly installed. Use the light button for Morse messages or for secret signs that no one else knows.
3 Red and green Behind door number 3 you will find a green LED. Integrate them into the circuit as shown in the picture. Then both LEDs will shine together, the red one and the green one. And switch 1 can switch both on and off at the same time. Series connection In series connection, the same current flows through two or more users. It’s an “unbranched circuit” because the current runs in only one way. This means that the amperage is the same at every point.
4 Green turned off Open the 4th door and remove the cable with two plugs. If you install it along with the push button as shown in the picture, you can switch off the green LED by pressing the button. If the button is closed, you have built a by-pass for the electric current. The current then no longer flows through the green LED, but through the switch. The green LED goes off, but the red LED becomes a little brighter at this moment. In fact, the switch briefly closes the green LED.
5 Colour selector Behind door number 5 you will find a second cable. Use it to convert your circuit so that the red LED is not switched on until you press the push button. At the same moment the green LED will go out. With this switch you can change the colour: pressed = red, released = green. Once the switch is closed, both LEDs will be connected in parallel. One might think that current would flow through both and that both would glow. This is actually the case when the same LEDs are used.
6 Stored Energy On the sixth day on your calendar, you will find new component behind the door: a capacitor. It is a small, light brown disc with two wires. On it you will find the inscription 104, which stands for 100 nF (100 Nanofarad). A capacitor can be charged and discharged. If you set the main switch 1 to ON, it is charged. You can then turn it off again, wait a little and press the button. This creates a small LED flash that discharges the capacitor.
7 Coloured flashes of light Behind the seventh door you’ll find another cable. Now build your circuit and insert the red LED. Pay attention to the direction of installation! The red LED appears to be installed the wrong way around, i.e. with the cathode towards the positive pole of the battery. Using the button, you can alternately charge (contact open) or discharge (contact closed). When charging, a green flash of light is generated, when discharging, a red light appears.
8 Electrical noises Open the 8th door and discover a small piezo speaker with two wires. The connecting wires are very thin and soft and must therefore be protected just like the battery cables. Make two more holes in the protective foil of the adapter board and guide the wires through from below. Then feed them through the holes provided, where they should stay until the last experiment.
9 Braked current Behind the 9th door you will find a new resistor with the colours brown, black and green. It has 1,000 kΩ (Kiloohm), so a 1 MΩ (Megaohm). This very large resistor provides a very small current that only slowly charges the piezo transducer. Open and close the contact several times. Both LEDs will clearly flash. But the piezo speaker only produces a crack when the contact is closed. Once again you can also use a wire or other metal object if the button is too loud.
10 Light flashes without battery Open the 10th door and remove another resistor. It is 2.2 kΩ and has three red coloured rings. Now build a circuit with the piezo speaker, the resistor and two LEDs. The battery is not connected and may be removed from the battery clip. The push button should be pressed for the first experiment. Now lightly tap the piezo disc. This will again result in weak red and green flashes of light. Attention! You must not use too much force, otherwise the ceramic disc could break.
11 Amplified current On the eleventh day you will receive an important component of your calendar: the transistor. The transistor has three connections which should not be confused with each other. They are called emitter (E), base (B) and collector (C). By the way, the abbreviation C comes from the English spelling (collector). The emitter should be connected to the negative terminal of the battery. The flat, labelled side of the transistor must point to the left.
12 Amplified light flashes Behind the 12th door you will find a resistor marked 330 kΩ (Orange, Orange, Yellow). Integrate it into this amplifier circuit using a transistor. If you now tap softly on the piezo disc, the red LED will emit a strong flash. But weak flashes of light also come from the green LED. Please note that the green LED is installed in a different way than normal, namely with the anode (long wire) at the minus pole of the battery.
13 Touch switch Behind door number 13, you will find a second transistor of type BC547. Along with the first transistor, it should now provide even more amplification. Both collector terminals are directly connected, and the emitter of the first transistor leads to the base of the second transistor. This circuit is called a Darlington circuit. With this a touch switch will be built here.
14 The light sensor There is a yellow LED behind door number 14. You could install it in your circuit instead of the red or green LED and try out another colour. But it can also perform a completely different task. In this experiment, the yellow LED is used as a light sensor. When illuminated, it delivers a very small current, similar to a solar cell. This is then amplified by two transistors and causes the other two LEDs to shine. Do not install the capacitor first. Test the experiment using a flashlight.
15 The motion detector Behind the 15th door you’ll find another cable. You will be building using an infrared motion detector. The actual sensor is the piezo disc. You already know that when the temperature changes, it generates an electrical voltage. And this also works without direct contact if you get close. It is even better if you darken the silver layer of the disc with a soft pencil. Your warm hand radiates infrared heat. When it hits the blackened sensor, it heats up a little.
16 One light amplifier Open door number 16 and take out a new component. At first glance, it looks like an LED in a clear housing, but in fact it is a light sensor; more precisely, a photo transistor. Install it along with a resistor and an LED. Make sure you install it the right way around. Unlike what you know about an LED, the long wire has to be connected to the negative terminal, because that is the emitter. The red LED lights up brighter when more light falls on the photo transistor.
17 Fototransistor/LED-Flipflop You’ll find another cable behind door number 17. Now you are going to build a circuit with an LED and a photo transistor that switches each other on or off. Bend the wires to fit so that the LED is mounted opposite the phototransistor and illuminates it directly. For this reason, the switchedon state is maintained even in the dark. But if you put a sheet of paper between them, the LED will turn off and won’t turn on by itself when you pull the paper out.
18 Key switch Behind door number 18 you will find another resistor with 1 MΩ (1 MOhm, brown, black, green). With this you’ll be building a button switch. Each press on the button changes the state of the LED to On Off - On - Off and so on. The last state is retained after release. Here, too, the speaker can remain connected. You will hear a click every time you switch. This circuit is also called toggle flipflop. If you press the button ten times, the LED is on exactly five times during this time.
19 Button switch Open the 19th door and remove the resistor with 4.7 kΩ (yellow, violet, red). Now build a flipflop that turns on the LED for a short time each time you press on the piezo disc and then turns off by itself. It is often enough to tap on the table next to the sensor. This time there are two LEDs in series at the output. A circuit like this is called a monostable flipflop. This means that there is only one stable state, in this case the off state.
21 A tone generator Behind door number 21 you’ll find a capacitor with 10 nF (overprint 103). Now build an electronic sound generator. You will hear a uniform sound from the speaker. Touch the condenser with your fingers so that it heats up a little. The tone changes very slowly. Touching the piezo transducer also changes the sound. with 10 nF with the larger one with 100 nF. The tone is now much deeper and more like a rattling. The sound can be changed by partially holding the sound hole of the speaker.
22 Flashing LED Door 22 hides a larger capacitor with 22 µF (22 microfarad). It is an electrolytic capacitor (electrolytic capacitor) that has a positive pole and a negative pole. Make sure you install it in the right direction. The negative pole has a shorter wire and is marked with a white line. A microfarad is 1,000 times larger than a nano-farad. 22 µF is therefore 220 times more than 100 nF. Put the electrolytic capacitor in the circuit of the last day.
23 Automatic colour change Open door number 23 and remove the very special LED in a clear housing. It actually contains three LED crystals in the colours red, green and blue (RGB) as well as a controller that switches the individual colours and fades them into each other. If you look into the RGB LED from the front when it is switched off, you can see the individual parts. Like a normal LED, the RGB LED also needs a resistor in series. The piezo speaker is also connected for this test.
24 Four-way flashing light Behind the 24th door you’ll find a resistor with only 1 kΩ (brown, black, red). It is used to achieve a larger LED current and more brightness. The circuit uses all LEDs together. All show a flashing flickering light controlled by the RGB LED and transistor. In addition, the photo transistor is built in to switch off the flickering at high brightness. With this, you can build a Christmas LED lamp that only becomes active in the dark.
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