The signal from MSP430 PWM pin isn`t quite ready to drive a speaker or amplifier. First, we can clean up the signal a bit by running it through a low pass filter. This clips the sharp edges from the PWM waveform to make it sound a bit more natural. You can calculate the ideal low pass filter for a given frequency with a calculator like this. I u
Click here to download the full size of the above Circuit.
sed an 8000Hz frequency because I eventually plan to play and record about 8000 samples-per-second with the digital voice recorder. Note that this is just a fraction of the 48000 samples-per-second used by CD players and PCs. At 8000Hz my ideal low-pass filter has a 0. 01uF capacitor (C1) and a2K ohms resistor (R1). Finally, it`s proper form to block any DC voltage from the signal path using an electrolytic capacitor (POL-C1). The capacitor allows only the AC waveform to pass out of the circuit. A value between 4. 7uF and 47uF seems to work fine. I didn`t notice a difference among the range of values that I tried for the quality of audio produced. This capacitor is usually not necessary, as most amplifiers have a similar capacitor at the audio input connection. Test program 1 (test1 in the project archive) creates a 50% `on` signal with the PWM. This generates a continuous tone from the speakers. See it in this short video clip.
This project fits more for custom made battery casing that can have more space to hide things inside. This switch with few alterations can be used for any other project as well but is designed based on e-bike needs! This project use a clever functionality of....
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....
Many times for various reasons we forget or can not water the plants that we have in our homes. And many humidity sensors units just notify us with a beeping sound or with a flashing light, that the pot needs watering. But what if we are away from home? This....
The principle behind a metal detector is really very simple. Proof of this is the circuit that follows, in which it proves that the construction of a metal detector can be done in the minute, with few components that we find very easily everywhere. With the....
The sub-harmonic bass generator is a sound producing unit for guitars. The sound it produces looks very much like that of the bass guitar. The octave generator is sometimes quite unusual since it does not produce any of the usual ways of coloring the sound,....
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.....
characters left: