Simple Arduino Capacitance Meter

Description:
This is a device to measure the capacitance.It is constructed using the arduino bord.It just consist of a fixed resistor and a capacitor whose value is to be measured.Its practical measuring range is limited to 200nF to 300uF due to various reasons.
Principle of working:

Its principle is very simple.The capacitor shown in the figure is is fully charged and then allow to discharge through the resistor of fixed resistance.The discharging equation is given by .So  initial voltage of the capacitor V₀ become constant.If we fix the V(t), it will also become a constant.Anyway resistor is fixed.So if we write the equation for capacitance from this equation, it clearly shows that the capacitance is linearly varying w.r.to time.It means if 1uF capacitor takes 1ms to discharge from 5v to 1v,then 2uF should take 2ms to discharge fro 5 to 1v.So we are measuring the time taken by a known capacitor,and using linear relationship we can calculate the unknown capacitor value.
Construction:
The pin 1 is connected to digital pin 7(d7),of the arduino.And the pin 2 is connected to the analog pin A0 (a0)in arduino.First we need to charge the capacitor fully.So configure d7 as output and give a high voltage,configure a0 as output and give a high voltage.Give a delay time to charge the capacitor fully.After the delay make d7 low and configure a0 as analog input.The capacitor will immediately start discharging and the reading will be measuring in a0.Start the inbuilt timer to calculate the running time.After the capacitor voltage decrease to certain value say 2v, stop the timer and calculate the time.At first time we should be knowing the capacitor value.Using this data the
C_unknown=(Time taken for unknown X known capacitance) /(Time taken for the known capacitor);
Use the lcd to display the output.For very smaller value of capacitors the dischage time will be in nanoseconds.So we are ending up with more error.By choosing the resistance of higher value the range can be increased.
arduino code:

#include <LiquidCrystal.h>
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);
void setup() {

TCCR1B=0x00; //stop timer
TCCR1A = 0x00; //normal timer mode
TCNT1=0x00;//initial value of the timer
pinMode(7,OUTPUT);
digitalWrite(7,HIGH);
pinMode(0,OUTPUT);
analogWrite(0,255);
delay(3000);//charging the capacitor
digitalWrite(7,LOW);//start discharging
pinMode(0,INPUT);
TCCR1B = 0xC3;//start timer
int x;
while(1)//wait in the loop until cap discharge to 2.5 volts.
{
  x=analogRead(0);
 if(x<=410)break;
}
TCCR1B=0x00; //stop timer
long k;
k=TCNT1;//final value in the timer
double c;
c=(10000*k/2348);// for 10000 nF it took k=2348.
lcd.begin(16, 2);//start timer (clock prescaler /64)
if (c<1000) {lcd.print(c); lcd.print(" nanoF");}
  else {lcd.print(c/1000.0); lcd.print(" microF");}

}
void loop()
{

}

Implementation In LabView

If u have any suggestion in improving this please feel free to comment.
Have fun....
Team members:
Dheeraj kumar C.
Kumar bharath
Darshan ramakant.

                                       Cellphone Operated Robot

Description:
It is basically a robotic car which can be controlled using mobile phone.The key component in this robot is DTMF decoder ic.It takes the dualtone frequency as input and produces output in binary form.In cellphones when we press any key we will listen different tones.That tone is a linear combinations of two sinosoids of different frequencies.Here is the table.

The dtmf decoder takes these frequencies and gives binary outputs.We will give the input tone to dtmf decoder using audio jack from phone 1. We call this number using phone 2 and press buttons,the tons will go to decoder through adio jack and the ic will produce different binary outputs for different key pressed.These binary output can be used to control the robot using microcontroller.
Circuit:

The tip is connected to the tip of the adio jack.ring is connected to the bottom ring of the adio jack.

The two other end points in right side of dtmf circuits  are connected to the 9v battery.The output will be taken from Q1 to Q4.The output buffers are not necessary.

Connect the other end of the jack to audio pin of the phone.Keep the phone in automatic answer mode.Call this number from other phone.As u press the keys the output starts coming.Put LED's to test.When u press 1 in mobile Q1=9volts,Q2=Q3=Q4=0.Similarly when u press 2, Q2 becomes high and so on.These outputs are taken and given to 8051 micro-controller.The output of the microcontroller is given to the H-bridge ic to control the motor rotation of the robot.
So we can control this robot almost anywhere in the world,if u can establish call from a mobile to the cellphone in the robot! The area of operation is same as the area of the service provider.
Not only this robot we can trigger any circuit by using this amazing ic.
You can see the final product video at this link

Team members:
Dheeraj kumar c
Kumar bharat
Darshan ramakant



Have fun..

My theme

Hello guys.This is my small attempt to do something in electronics.First of all let me tell about myself.I
am  from a small village in the Karnataka.Now i am doing engineering in PESIT Bangalore in electronics.                                                                                                                                                  
                What i have seen so far is most of the technical people are contributing to domain which is mainly  related to the entertaining field.For example many apps now available are to entertain the people and helping the people to pass the time.But we are forgetting the primary part... agriculture ,farmers who are feeding us.There are lot of problems in that field.Recently what i have seen is there is lot of shortage of manpower in that field.every one wants to get a job in an air conditioned office.No one is preferring to work in the field.As i am also in that traditional path i have no moral rights to force anyone to choose agriculture.But i want to help them through the technology.We can do something to help them.
        I will be uploading the projects we did.These projects may not entirely our own.We might have copied the circuits from the other sites.But the whole idea is to build something  from which we know.
You guys are always welcome to give suggestions...