Building microphone preamp for microcontroller analog input

Microphone is another analog signal sensor which converts sound wave energy into electrical signal. Some microphones does this directly (dynamic microphones), some need additional electrical source like electret. Electret microphone is simply a capacitor which one moving diaphragm which by moving changes capacitance. It can be captured with simple RC circuit. But the signal is very low and barely detectable with microcontroller ADC. This is why normally there are microphone preamp used that gains microphone signal, filters it and gives a DC offset so it would fir perfectly to full rail of ADC input.


David actually have made two iterations of microphone preamp circuits. Previous was NPN transistor based which performed pretty good, but this time he wanted to bet even better signal and so he used operational amplifier. He selected TLC272 opamp which can work from single rail and down to 3V which makes it ideal choice for 5V and 3.3V microcontroller circuits. He found that this circuit performs pretty good even on low sound and produces lower noise than NPN version. Bellow you can see how he tested the circuit. Continue reading


Keep your plants watered with this watering system

If you like growing plants at home, then you know that they are restricted in space and climate. There are some things that you can do and there are that you can’t. You cant control the temperature and light much especially in areas where you live or work. It can be put near the window and temperature is mostly a room temperature. But there is one parameter that can and must be kept in mind – moisture. It is vital to almost any plant to keep soil at some moisture level and this is what you cannot ensure properly unless you keep checking it constantly. So why bother when this work can be done by putting a simple circuit.


Frank Donald built a really simple setup that works on Atmega16 based circuit. Microcontroller here is to read soil moisture sensor that comes as cheap module which includes comparator. So it gives high signal when soil is dry and low when wet. But to make it a bit smarter, he is reading analog signal from sensor, so microcontroller could read this signal and according to its level control a relay to water pump. By setting some thresholds he made simple hysteresis to prevent relay from chattering.

In other hand similar result can be achieved much simpler – you can connect sensor digital output directly to relay driving transistor and have similar result.


Phoenard is a great helper for Arduino beginners and pros

When you are just starting to learn electronics or program microcontrollers it is great to have a friend who knows how to do it properly. But hardly everyone can have such babysitter near by so you go to internet and try to surf for best tutorial that would be easy to follow. But Assen – the creator of Phoenard project thought that learning can be really fun with right tools. So he created a cool Arduino compatible gadget that can be used as hand-held gadget for learning prototyping.

The gadget is stuffed with lots of features controlled by Atmega2560 microcontroller (Arduino Mega). There is a large color display with touch screen so user could easily interact with programs. Phoenard is intended to have two major purposes – first of all to serve as prototyping platform, where it can be used to build circuits by following visual and audio instructions and then test it by plugging prototyping board to gadget for testing. Once you’re done with prototyping, then you can use it as everyday portable gadget. It can hold thousands of custom sketches that would do different task – just like aps in smart phone. It has graphical user interface which makes it easy to access programs, modify or even draw an icon. With GSM +GPRS it can be used as phone, with GPS as navigator, linked to other devices with blue-tooth or RF or used as MP3 or MIDI player. There are even more sensors added that we dont even try to mention.


Bringing emotions from outside with LUZ ring-light

Color and light can have a significant effect on human emotion. They can be used to set romantic feel with warm reddish light, or refresh when blue light is used. Following project seems to be really interesting and very useful in some areas. It is called Global Emotional Lighting. The idea was to build a lighting ring, that would bring emotions from outside weather conditions. One good use for this is in areas, where people lack of sunlight. For instance who are sick, or simply must work indoors all day.

Technically speaking, this project is built around Arduino which takes measurements from outside with light and temperature color sensor (Adafruit TCS34725). Then this captured data is reflected on RGB LED stripe ring. The ring and sensors can be located in different places, because they communicate through RF interface. As you can see in video this work is really scientific and really well polished so everyone could enjoy the result.