This project uses a small, common electret microphone to convert audio to an electrical signal. These are the cheap microphones found in most PC headsets. The microphone output must be amplified and zeroed before it can be recorded with the MSP430. This is done with an operational amplifier, or op-amp. The op-amp amplifies the tiny, oddly centere
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d audio signal into a full range signal based on 0 volts. The diagram shows the original signal (blue) and the amplified, full range signal outputted by the op-amp (red). I`m not much of an analog designer, so may I refer you to any of these tutorials on op-amps if you need more info: wikipedia, a flash tutorial, opamp basics. The op-amp design I used came directly from TI`s digital audio recorder application note slaa123 [pdf!] (page 3). TI`s design uses a TI TLV2252 dual op-amp. We only need one, so I substituted a single channel TI TLV2221 op-amp. I used the circuit and values from the TI app note, but substituted the 2K/. 01uf low-pass audio filter I chose in part II. The TLV2221 is only available in a surface mount package. If you want to do an all through-hole version of this project, consider a TLV2252 based design. We`ll use the MSP430`s on-chip analog-to-digital converter (ADC) to measure the audio signal. The ADC is a pin that measures analog voltages. Measurements taken by the ADC are recorded as a fraction of a voltage reference (Vref). In the prototype, the voltage reference will equal that of the circuit - 3. 3 volts. The smallest voltage change that can be measured by the ADC is denoted in bits. An 8 bit ADC measures voltage on a scale of 0 to 255. A reading of 127 (127/255=50%) from the ADC represents ~1. 65 volts (0. 50 * 3. 3 volt reference). The diagram shows the relationship between bits, voltage...
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The circuit described here uses ultrasonic oscillations and operates based on the propagation velocity of these oscillations in the air. Thus, we can easily determine the distance of two points if the time within which the wave travels this distance is....
Sometimes the precious metals are hidden too deep and are not detected except with complicated devices. In many cases, however, small pieces of precious metal buried near the surface can be detected by relatively simple means. Everyone is very attractive to....
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In the past the sounding (sea bottom measurement) was done with the "bullet", that is, with a heavy lead object that the seamen plucked into the sea hung from a calibrated rope. As soon as the "bullet" reached the bottom, the depth appeared directly from the....
This Amplifier was designed to have the following specifications: Distortion less than 0.1% at full power of 100W even at 20KHz. Power has to be attributed to an extended bandwidth. The output transistors must be protected against short circuits. The power....
A series of LEDs serve to alert the gardener when plants need water. Using two conventional digital integrated LEDs and a series of LEDs, we make a very useful device for gardening. The device detects the amount of water in the pot and alerts the grower.....
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