![]() ![]() To do this experiment you will need the following materials and equipment: HyperPhysics, Department of Physics and Astronomy, Georgia State University. These references have information on piezoelectricity and piezoelectric sensors:.This project is based on a website by Adam Kumpf, a former student in Media Arts and Sciences at the MIT Media Lab:.How does a piezoelectric device transduce mechanical strain into an electric current?.Understand the following terms and concepts: To do this project, you should do research that enables you to If you're interested in electronics and like to play acoustic guitar, this could be the perfect project for you. Or you could build a single pickup and compare the performance of the pickup when it is placed in different locations on the underside of the bridge, or with or without foam. You could also compare the performance of your homemade pickup with the performance of a professionally-designed piezoelectric pickup. For example, you could purchase several different piezoelectric elements with different specifications, and compare their performance as pickup devices. There are several different experiments you could try with this project. In this project, you'll learn how to make a piezoelectric pickup for an acoustic guitar, using inexpensive components that you can find at your local Radio Shack store. Unlike a microphone, with a pickup you will not record extraneous sounds from elsewhere in the room, just the sound of the acoustic instrument in which the pickup is mounted. With a pickup, the vibrations of the instrument are transduced into an electric current, which is then amplified and recorded. The piezoelectric effect can also be used in electronic pickup devices for recording acoustic instruments. A preamplifier in the phono cartridge of the turntable amplified these tiny currents, which were then further amplified by the stereo amplifier so that we could hear the music through speakers. The pressure transferred to this second crystal creates tiny electric currents due to the piezoelectric effect. The sides of the groove exerted pressure on the stylus, causing it to move a lever which is attached to a second crystal. To play the signal back and hear the music, the record was spun on a turntable, and a diamond stylus on the end of the tone arm would ride through the groove. The audio signal was recorded in grooves cut into the records. If you use a lower input resistance amplifier, you'll need to pad the output of the transducer with a capacitor to flatten the low frequency response which will cause a loss in amplitude response.Back in the day, before any of us had computers at home, we listened to music on vinyl records. Plus, making a step down transformer with a 100:1 impedance ratio (10:1 voltage ratio) will attenuate the signal which will degrade the signal to noise ratio (not good).Ĭonclusion: Stick with the preamp approach and use a preamp with an input impedance above 6.4 M \$\Omega\$. The magnetizing inductance calls for a primary inductance over 20k Henrys (magnetizing inductive reactance needs to be a few times higher than the transducer impedance). Using a transformer at this high impedance is not practical. Assuming you want a low-cut frequency of 50 Hz, Rin would need to be 6.4 Megohms \$ (1/(2 \pi\ f\ C) = 1/(2\pi\ 50Hz\ 500pF)) \$. ![]() Higher Rin will make the high-pass cutoff frequency lower and will also lower the input noise. The amplifier input impedance will determine the low frequency response of the system and also equivalent input thermal noise. Simulate this circuit – Schematic created using CircuitLab I couldn't find electrical data on piezo guitar pickups, but one source said the simple capacitance of typical guitar piezo pickup is around 500pF to 800pF. Near resonance (one source said around 4.6 kHz), the impedance is complex and the amplitude response will peak. At low frequency, a piezo transducer can be modeled as a capacitor and a voltage source as shown in the schematic.
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