So the concept here is pretty simple. I wanted to mount a microphone on a stick with an LED and design a circuit that would react to a large amount of noise on the microphone input (blowing) to turn off the LED. As you might expect, the schematic for this thing is very straight forward. The device is powered by a CR2016 3V coin cell battery which
Click here to download the full size of the above Circuit.
always supplies power to the circuit (there`s no power switch). If left in, even when the LED is turned off, the battery will die, but I figure for something with such a limited one-time use, it was an acceptable requirement. The left side of the circuit is the familiar gain stage/envelope follower that you`ve seen in many of my sound reactive circuits. I left the low pass filter in (R6 and C7), though it`s not really necessary. The only difference this time is that there is no gain on the microphone. Typically, blowing on a microphone actually clips the mic which means you`re producing the largest electrical signal possible. I experimented with different gain levels until I realized that anything more than 0dB gain caused the candle to be too sensitive and made it blow itself out. Originally, I was hoping to flex my analog muscles and make a straight up FET gain stage, but I realized that with a CR2016 battery as my voltage source, there would be too much variability on the rail to set a good bias point. The second half of the circuit is a standard BJT flip flop. You probably saw a lot of these in my transistor clock posts. This is a "bi-stable" circuit which means it must always exist in one or two states. Specifically, either Q2 is on and pulling current down through the D2 (the LED) and keeping Q1 off, or Q1 is on which keeps Q2 off. If you try modeling a circuit like this, you might find that it can balance between...
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: