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 the 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 the Atmega16 based circuit. Microcontroller here is to read soil moisture sensor that comes as a cheap module which includes a comparator. So it gives a high signal when soil is dry and low when wet. But to make it a bit smarter, he is reading an analog signal from… Continue reading

Home made Geiger counter

Radiation is a harmful process which cannot be sensed by human. Normally you don’t need to measure radiation level but if you think there is a risk then it is worth checking. Changpuak have designed a homebrew Geiger – Müller counter using a counter tube from Distrlec. In order to use such tubes there is a high voltage needed (~500V). So he split his design in to two parts that evolved in to two separate PCBs. First one is dedicated to generating high voltage using standard chopper circuit using 555 timer chip. It rises voltage from 9V up to 400-900V. Second PCB holds Geiger tube, Atmega16 microcontroller and MX232 for USART communications. Also value is displayed on standard LCD screen. This counter is able to detect β and γ radiations that are deadly to human. Continue reading

A DDS function generator using an ATmega16

I can still remember the piece of rectangular box with lots of buttons labeled 1kHz, 10kHz, 100kHz, 1MHz and everything else in between. Oh it also has a knob connected to a dial dividing a sector into a hundred parts with a series of 7 segments changing dial every time a button is fired– just like old school radio we see at startrek. We commonly call it the function generator and its usually used to inject square waves into your circuits – what for? Mostly for clocking. Here’s a new implementation of the AVR DDS function generator 2.0 (, it has a different board layout and uses only through hole components for easy construction. It has two outputs one for a +-5V signal source the other is a 0-10V signal source, the voltage levels of the two outputs are reconfigurable using two separate potentiometers. Like the original version it incorporates a 2×16 LCD screen and push buttons for control – press a button to start and stop the signal generation. The circuit’s DAC is just a simple R-2R ladder controlled… Continue reading