The number of cycles per second is called frequency. The unit for frequency is the hertz (Hz). Figure 1. Wikipedia Contributors. Grundsätzlich gilt bei allen Messungen, die Sie vornehmen: immer den Messbereich so wählen, dass man eine vernünftige Anzeige erhält, mit möglichst vielen angezeigten Ziffern. In our guide we're using the Fluke 117, we chose the Fluke because they're a great all round multimeter and they have the symbols and settings that you'll find on 95% of the multimeters on the market. How can a crystal radio generate sound without being connected to a power source like a battery? Then, as now, the radio acted as a gateway to the world. Cut a segment of the enamel-coated magnet wire about 6 inches long. It is an electrical circuit that can pick up and play sound from AM radio stations. Take your crystal radio outside and hook it up to your antenna and ground rod. Wenn Sie es umgekehrt machen, erhalten Sie ein Minuszeichen vor dem Wert, den Sie ablesen. Tighten the screws to hold the capacitor in place. 2–3 ft. into the ground, preferably near the end of the antenna that has extra wire to attach to your radio. These wires are also used to form the circuit by connecting resistors, switches and other components together. Do not tighten the screws all the way yet. Fortunately, the current symbols on multimeters have been more or less standardized by one of the most popular brand of multimeters, Fluke. FM stands for, DIY Glitter Surprise Package with a Simple Circuit. If you have any comments (positive or negative) related to purchases you've made for science projects from recommendations on our site, please let us know. The diagram in Figure 2, shows the parts of a crystal radio: antenna, tuning coil, diode (labeled as "detector"), earphones, and a connection to an electrical "ground." You can also try using a different ceramic capacitor (see question below for details). Move the tuning rod all the way to one side of the coil. The tuning coil, showing exposed copper, after sanding off insulation where the tuning rod contacts it. Ask yourself a couple questions: Is there any correlation between location on the map and how loud/clear the stations sound on your radio? Figure 11. Auch wenn das Multimeter keinen Kontakt mit einem Stromkreis hat, kann, insbesondere im mV-Bereich, eine Spannung angezeigt werden, die durch ein Magnetfeld induziert wird. Wrap the capacitor, resistor, and diode leads around the screws under the appropriate clips, as pictured. Ein Zangenmultimeter hat fest angebaute Zangen. Every AM radio station transmits its signal at a given frequency, and the frequency band for AM radio stations in the United States is from 530,000 Hz to 1,710,000 Hz. Continue tightly wrapping the coil until you reach the set of holes on the other end of the cardboard tube. One of the best reasons to buy a clone is the fact they are generally less expensive than their official counterpart. Make interactive makerspace projects while learning to code and problem solve. Our top priority is student learning. Home Science Tools, Dieser geringe Strom lässt die Messung unverfälscht, zeigt aber auch Spannungen an, die schon bei kleinster Belastung zusammenbrechen würden. Radio stations send out waves, and the radios in our homes receive those waves. You may be wondering what an Arduino board can do besides blink an LED. When a capacitor and an inductor are combined in a circuit, it is called an LC circuit for short. For example, does your radio do a better job picking up stations that are closer to your house? You’ll find a link to “I Did This Project” on every project on the Science Buddies website so don’t forget to share your story! We’ve found that a lot of maker educators haven’t taken the plunge into coding or Arduino because they think programming is scary. Überprüfen Sie, ob sich das Multimeter im richtigen Messmodus befindet, bevor Sie eine Messung durchführen. The old-fashioned crystal radio in Figure 2 just relied on the capacitance of the antenna itself, but adding a separate capacitor allows for better tuning. But if someone whispers to you from across the room, the amplitude of that sound wave is very low. Um das Multimeter in den gewünschten Messmodus zu versetzen, drehen Sie den Wahlschalter auf die gewünschte Position. If you search the web, you will find there are hundreds of Arduino compatible clones and variations available but the only official boards have Arduino in it’s name. Attach the split ends of your audio cable to the two "HEADPHONE" Fahnestock clips, and plug the other end into the audio amplifier's "Input" jack. A: The capacitor helps determine the resonant frequency of your crystal radio circuit (see the technical note in the Background tab). A larger capacitor will. DCA). The last method would be to use a 9V AC power supply. Stellen sie am Multimeter die gewünschte Messfunktion (Gleichstrom oder Wechselstrom ein (siehe 3.1 Wahl der Messfunktion). This procedure is a suggestion, but you may need to modify it based on your location. In this example, we use a momentary push button switch to blink an LED. Figure 23. (Top) A 1-cycle wave, and (bottom) a 3-cycle wave. Using a breadboard allows you to create temporary prototypes and experiment with different circuit designs. Place your sandpaper between the brass rod and the coil wire, and pinch it around the tuning rod, as shown in Figure 13. Stations that transmit signals via amplitude modulation are called AM radio stations (as opposed to FM stations, which use frequency modulation, but these will not be discussed in this science project). Does this affect the reception of different stations? How does this affect the resonant frequency range of your radio, and your ability to tune in to different stations? (Nur in Sonderfällen, Stellen sie am Multimeter die gewünschte Messfunktion Widerstand (. Figure 19. Try using your radio at night — can you pick up any stations that you could not detect during the day, or vice versa? Attach the cardboard tube to the wooden base board using two #6 x ½ inch screws (these are the smaller screws that came with your kit; notice how the other types of screws are larger) and your Phillips head screwdriver. You can click on a station's call sign to bring up more detailed information, including the coordinates (, Use an online mapping program like Google Maps, Print out a paper map of your area, or use an online mapping tool like Google Maps or Google Earth. You can print and cut your own labels if you want. Achten Sie darauf, dass auch der entsprechende Bereich (10. You can learn more about some of the concepts listed below at the Science Buddies Electricity, Magnetism, & Electromagnetism Tutorial. More and more makerspaces around the world are looking to add coding and electronics to their maker education programs. Figure 7. A diagram of the various parts of an early crystal radio. Please enter a search term in the text box. Manche Instrumente verfugen uber eine spezielle Betriebsart mit der Bezeichnung Diodenprüfung. Daher muss der Stromkreis nicht aufgetrennt werden. Loop the stripped portions of the tuning coil wire under the top "HEADPHONE" and "GROUND" clips. Be sure to remove the insulation around the entire perimeter of the wire. One of the best ways to do this is by integrating an Arduino board into makerspace projects and lessons. Jameco Electronics. Zum Ein- oder Ausbau des Strommessgerätes muss der Stromkreis abgeschaltet und aufgetrennt werden. Now, begin to carefully and tightly wrap the magnet wire around the cardboard tube, starting just above the holes you just threaded. Verwenden Sie das Messgerät nur in Umgebungsbedingungen (Temperatur, relative Luftfeuchte und Höhe über dem Meeresspiegel), die in den technischen Daten des Multimters angegeben sind. Very high, Compared to a typical science class, please tell us how much you learned doing this project. If you purchased a ground rod, have an adult use a mallet to pound it at least Wenn die Messfunktionen auf der Wahlscheibe nicht nach Gleich- und Wechselgrößen unterschieden sind, erfolgt dies über eine Taste, die meist mit Select, Func oder AC/DC beschriftet ist. Much more. Connect the "ANTENNA" screw, the tuning rod screw, and the detector tie point screw with an extra piece of 6 inch wire. If someone yells at you from across a room, the amplitude of the sound wave is high. You may hear a buzzing noise from other nearby sources of radio waves, like TV stations or airport radar, but FM stations will not be heard at all. Modern radios use a diode instead of a crystal. Figure 18. Our top priority is student learning. Because of it’s flexibility and low cost, Arduino has become a very popular choice for makers and makerspaces looking to create interactive hardware projects. The direction of the capacitor does not matter. The following 15 second video gives you a quick idea of how a breadboard, Arduino, jumper wires and the sketch work together to perform a function. Hold Button. In reality, there are many variations of the official Arduino boards and then there are hundreds more from competitors who offer clones. How does changing the shape and orientation of your antenna affect your radio's reception? Connect the ends of the audio cable to the two "HEADPHONE" Fahnestock clips, as shown in Figure 18. Cut a segment of enamel-coated magnet wire that will be long enough to reach from your ground rod to your radio, with an extra 2 ft. to wrap around the ground rod. Legen Sie niemals eine höhere Spannung oder Stromstärke an die Messbuchsen an, als die in der Anleitung angegebenen Maximalwerte. void loop() – Contains the instructions that get repeated over and over until the board is turned off. Slightly bend the ends of the leads of the diode, and loop these around the screw for the "HEADPHONE" clip and the detector tie point screw, as shown in Figure 12. Can you use a multimeter to measure the current and voltage delivered to your audio amplifier from the radio circuit, and use them to calculate the electrical power of each radio station you receive? When radio stations transmit electromagnetic waves, they can vary or modulate the amplitude of the wave and that is one way we hear the different levels and frequencies of sound. Science Buddies, a 501(c)(3) public charity, and keep our resources free for everyone. Are you planning to do a project from Science Buddies? All rights reserved. Radio waves have energy associated with them. Be sure to sand off insulation in the appropriate spots first. Figure 9. This setting allows you to examine and test small electronic circuits, … Now, compare the stations listed on your map to the stations you marked on your strip of masking tape. A: Your crystal radio will only work to listen to AM radio stations. Do not tighten the screws yet. Write to us at What can I do? Historically, some prisoners of war had to be resourceful and do just that. Rather than rely on outside electrical sources, like a batteries or plugs, crystal radios get their power directly from the radio waves. The tuner coil in the circuit is also called an inductor. Optional: before you continue with the rest of the project, you can decorate your wooden base board using paint, markers, or other materials.