555 timer is the most standard IC circuit, so I am going to skip its working, fundamentals and come straight to the point. 555 timer is mostly used as an oscillator. The frequency of oscillations is controlled by a RC circuit. A capacitor and resistor of known value are taken to make a RC circuit of desirable time constant. Enough of theory lets get to the fun part ( if you want to know the real mechanism of 555 then follow this link) . Below is the schematic of the circuit.


Check out how this circuit looks when its working:


A very basic experiment with Semiconductor Diodes


Diode is a two terminal electronics component which has low resistance to current in one direction but very high resistance in opposite direction. Today the most common type of diode is the one which has crystalline piece of semiconductor with a P-N junction connected to two terminals. Diodes do not follow ohm’s law. So its important to study their Current-Voltage characteristics (I-V curves). In this experiment we do exactly that. From these curves we find some important quantities like ideality factor and knee voltage. Ideality factor, also known as the quality factor  accounts for carrier recombination as the charge carriers cross the depletion region. The ideality factor ‘n’ typically varies from 1 to 2 (though can in some cases be higher), depending on the fabrication proce ss and semiconductor material and in many cases is assumed to be approximately equal to 1


Knee voltage is the voltage at which current through the diode is 1mA. It is a measure of how much energy is needed to push electrons through the diode. Temperature dependence of knee voltage is determined by placing the diode in thermal contact with hot water and allowing it to cool down. Knee voltage at different temperatures is determined and plotted in a graph (refer the pdf). From this graph we find out that knee voltage decreases with increasing temperature.  The equations used are written below and all data has been compiled in a pdf.

Laser Doppler Anemometry


This is one of my favorite experiment. In this experiment we take advantage of Doppler effect to measure speed of flow of liquid. A He-Ne Laser is used and laser beam is split into two parallel beams using a beam splitter and mirror. The two rays are then allowed to converge at a point in liquid where they interact with particles(silver-coated glass beads) in liquid. The diverging beams coming out of liquid are again converged at a point and a photo diode sensor is placed at that point to sense intensity. The intensity vs time pattern is analyzed and frequency is determined using Fourier transform. I have attached a sample Intensity pattern and its Fourier transform. Data and results are also included. You can view the actual documentation of this experiment here:




Although it’s a nice experiment to measure speed of liquid without actually disturbing it. It cannot determine direction of flow.


Hello, In the previous post, I mentioned the connections which should be made to use HD44780 16 by 2 LCD. In this project I will be exploiting some ideas from previous project to make  temperature sensor and displaying the temperature on the LCD. Also, I have incorporated a light intensity measurement cum theft detect device which Displays the light intensity of surroundings on the LCD and produces a beep sound whenever someone crosses the door(i.e. light intensity is close to(or is) 0). Now, I used LM335 sensor for measuring the temperature of the surroundings by exploiting the fact that any change in temperature will change the voltage of LM335( at 0 K Voltage is 0 Volts). And for the light intensity measurement(on a scale of 0 to 10) I used a Light depending resistance(LDR), whose resistance (therefore voltage) varies as per the intensity of light falling on it. When light of high intensity is falling on LDR its resistance is less and when light of low intensity is falling on LDR its resistance is more. I have uploaded the circuit diagram and the code(I have put some extra things in the code for example: the interface would ask options from user like whether you want to display temperature or light intensity which you may want to delete so make them as comments!).

The circuit diagram

in the circuit diagram i have connected ground of arduino board to 5v. Obviously its wrong, ground of arduino should be connected to the 0Volt line(the top one).

Click here for the code…

I have made a small instructive video. Hope you enjoy it!

HD44780 16 by 2 LCD DISPLAY…

Recently I was engaged in a simple but interesting little project i.e using 16 by 2 LCD DISPLAY through different microcontrollers like PIC16F877A and ATMEGA328(Arduino uno).


Here are some hints and the code which might interest some of beginners:

1.Make connections as follows:

  • LCD RS pin to digital pin 12.
  • LCD Enable pin to digital pin 11.
  • LCD D4 pin to digital pin 5.
  • LCD D5 pin to digital pin 4.
  • LCD D6 pin to digital pin 3.
  • LCD D7 pin to digital pin 2.
  • LCD VSS pin to ground.
  • LCD VCC pin to +5V.
  • LCD VCE pin to a 10K potentiometer(varying this resistance will vary the display).
  • LCD V+ pin to +5V or you can use a 100K potentiometer to vary the background led intensity)
  • LCD V- pin to ground.

2. Use the code(!245&authkey=!ADc69b5b17QKIjw) or create your own and enjoy!

LCD Hd44780


My name is Gagan and I am a  student at I.I.Sc. Bangalore. I am new to blogging and I have started this blog in my summer vacations(2013) to share some interesting electronics projects, programming projects. Expecting a lot of fun ahead!