This is one of my favorites. The LM386 is a low voltage audio power amplifier. It can provide 125mW to 750mW, enough for any project that uses audio. This circuit can work with batteries, requieres minimum external parts and works from 4 to 18 Volts (contact the manufacturer or read the technical info. Some versions works only with 5 to 15V.) The power output depends of the voltage. The power output is 125mW when the voltage is 6V. The voltage gain goes from 20 to 200 and the output is self-centering, so doesn't need dual voltage as other amplifiers. It can be used on battery radios, tape players, intercoms, also, as ultrasonic amplifier. This chip is the `555` of the amplifiers. Here is the typical application for this chip. Here are two schematics, the first one have a gain of 200 and the second one is only 20. You can use a switch for the 10uF capacitor to have the `boost` option.
Click here to download the full size of the above Circuit.
Click here to download the full size of the above Image.
The 10k resistor is used to adjust the sensibility if the electret microphone, the 100k resistor is used to adjust the volume. In theory, this circuit will not work because it needs a pre-amplifier. Supposedly, a 741 or any othe pre-amplifier is needed. As I said before, I don't follow the theory. I already verified that the pre-amplifier is not needed, just adjust the 10k variable resistor. In fact, You may not be able to get the circuit to work properly with a pre-amplifier. Warning: May be too loud The 220uF capacitor can be replaced by any other if that value is not available. Do not connect the speaker directly to the output pin. If you are using a tweeter (or piezoelectric) you can connect it directly. 7/9/2006 - UPDATE: This schematic can be used for almost ANY application that needs an amplifier. The switch labeled "Boost" activates the gain of 200 if the input signal is too weak.
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: