Monday, 13 October 2014

Greatness of Indian temples...

I watched this video from facebook and after watching this we would come to know about the greatness of Indian temples both in culture and also technically...

https://www.facebook.com/video.php?v=811439958877010

Saturday, 16 August 2014

High Temperature Alarm using NI MYDAQ

Present days detection of high temperature is important in industrial applications and also in some of the daily home applications .For knowing temperature and give an alarm for high temperature of  water, welding purposes, furnaces etc. So here I present a high temperature alarm circuit using LM 35.
Let us first discuss on LM35 which I used in this application
 LM35  whose output voltage is varied linearly with repect to temperature, but inversely proportional to the temperature.
Detectable range:-55 deg.C to 150 deg.C.  

Apparatus:
1) LM35 temperature sensor.
2) NI MY DAQ.
3) connecting wires.
Circuit which is interfaced with NI MYDAQ:
Step:1
Here +15 is connected to +VCC of LM35 and, AGND of DAQ to ground and output terminal to AI +1 and AI-1 to ground





Step:2
First calibrate output voltage to the detected temperature using multiplier and adder.

Output displaying temperature:
Step:3
Using comparator set a reference value:
Example: reference is 40
Temperature is 30. Then led is off (Boolean).
Here I used green one. But it would be better if we use red for danger.
Output when reference is more than detected temperature:
Output of  buzzer when reference is more than detected temperature.
  
Step4:
Output when reference is less than detected temperature:
Example: if reference value is 20
Detected temperature is 30
If we observe here led is glowing.i.e., representing more temperature.


Output of buzzer when reference is less than detected temperature:
If any queries, post a comment as well as you can contact me at kamalmohan.m1994@gmail.com

Monday, 11 August 2014

AMPLITUDE MODULATION USING MULTIPLIERS AND SYNCHRNOUS DEMODULATION USING PHASE AND FREQUENCY OFFSET ERRORS

Task1:                                                                                                                                                                            
  Consider a single tone modulating signal m(t)= cos10^3*pi*t , and  carrier signal c(t) =cos10^4*pi*t     
      Given that  Am=1,fm=500,Ac=1,fc=5000   µ=Am/Ac =1
A.M signal in time domain description is

            
In the time domain  
   Sam(t)= cos(2 π*5000*t)+1/2[cos2 π *(4500)*t]+1/2[cos2 π*(5500)*t]
In the frequency domain
                S(f)=1/2[δ (f-5000)+ δ (f+5000)]+ 1/4 [δ (f-5500)+ δ (f+5500)]
                                                                 +  1/4 [δ (f-4500)+ δ (f+4500)]

MULTITONE SIGNLAS:
Task2:
        Let us consider a multi tone modulating signal
                                  m(t) = 2cos1000p t -sin1500p +1.5cos2000p
For the given multi tone signal Am1=2,Am2=-1,Am3=1.5 &Ac=1 for carrier signal which is used in task 1 .  
Now A.m signal in time domain & frequency domain  as shown below
In time domain
                           S(t)= cos ( 10000pt)+[cos(2 *p*4500 *t)+ cos(2 *p*5500*t) ]
                                -1/2[sin(2*p*250* t)+ sin(2*p*1250* t)]
                            +3/4[cos(2 *p*4000 *t)+ cos(2 *p*6000*t)]
In the frequency domain
S(f)=1/2[δ (f-5000)+ δ (f+5000)]+ 1/2 [δ (f-5500)+ δ (f+5500)+ δ (f-4500)+ δ +4500)]
-1/4 [δ (f-5750)+ δ (f+5750)+ δ (f-4250)+ δ(f+4250)                                                          + 3/8[δ (f-6000)+ δ (f+6000)+ δ (f-4000)+ δ (f+4000)]
 
 

 
TASK-3:
 
DEMODULATED SIGNAL:
 
 
 

 
 
 
 
PHASE DEVIATION ERRORS:        Φ=45˚,90˚,135˚
 

 
 
FREQUENCY DEVIATION ERROS: Df = 500hz,1000hz,1500hz
 

 
 
DEMODULATION WITH PHASE AND FREQUENCY ERRORS:
 

MAT LAB program:
clc;
clear all;
close all;
fc=6000;% carrier frequency
fs=50000;%sampling frequency
f=500;%tone modulation
Am=1;
Ac=1;
t=0:1/fs:((4/f)-(1/fs));
 
%Task-1--------------Modulating wave-----------------
     
M=Am.*cos(2*pi*f*t);
m1=2*cos(2*pi*500*t)-1*sin(2*pi*750*t)+1.5*cos(2*pi*1000*t);
figure(1);
subplot(3,2,1);plot(t,M,'linewidth',2);
plot(t,M);
axis([0 0.008 -1.5 1.5])
xlabel('Time (sec)');
ylabel('Amplitude');
title(['Message Signal']);
grid on;
f_M=abs((fft(M,1024)));
f_M=[f_M(514:1024) f_M(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,2);
plot(f,f_M);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of Message Signal');
%----------MULTITONE SIGNAL---------%
figure(6);
subplot(3,2,1);plot(t,m1,'linewidth',2);
plot(t,m1);
axis([0 0.008 -1.5 1.5])
xlabel('Time (sec)');
ylabel('Amplitude');
title(['multitone Signal']);
grid on;
f_m1=abs((fft(m1,1024)));
f_m1=[f_m1(514:1024) f_m1(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,2);
plot(f,f_m1);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of multitone Signal');
 
%---------------------------carrier wave----------------------
 
C=Ac*cos(2*pi*fc*t);
subplot(3,2,3);
plot(t,C);
xlabel('Time (sec)');
ylabel('Amplitude');
title(['Carrier Signal']);
%grid on;
f_C=abs((fft(C,1024)));
f_C=[f_C(514:1024) f_C(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,4);
plot(f,f_C);
xlabel('Frequen;cy in Hz');
ylabel('Amplitude');
title('Spectrum of Carrier Signal');
%-------------------------------modulated wave---------------------
sam=Ac*(1+M).*cos(2*pi*fc*t);
subplot(3,2,5);
plot(t,sam);
xlabel('Time (sec)');
ylabel('Amplitude');
title('Amplitude Modulated Signal');
grid on;
f_sam=abs((fft(sam,1024)));
f_sam=[f_sam(514:1024) f_sam(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,6);
plot(f,f_sam);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of Amplitude Modulated Signal');
 
 
%----------------------Demodulation signal--------------------------
 
XC1=Ac*cos(2*pi*fc*t);
demod=XC1.*sam;
figure(2);
subplot(2,2,1);
plot(t,demod,'r','linewidth',2)
xlabel('time');
ylabel('Amplitude');
title(' Amplitude demodulated Signal1');
f_demod=abs((fft(demod,1024)));
f_demod=[f_demod(514:1024) f_demod(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(2,2,2);
plot(f,f_demod,'r','linewidth',2)
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of Demodulated Signal1');
 
F=1000;s=15000;
x1=demod;
[b,a] = butter(3,F*2/s,'low');
y1 = filtfilt(b,a,x1);
subplot(2,2,3)
plot(t,y1,'r','linewidth',2)
title('Demodulated Signal1');
xlabel('Time');
ylabel('amplitude');
 
 
%----------------------1st phase deviation--------------
 
XC1=Ac*cos((2*pi*fc*t)+45);
demod1=XC1.*sam;
figure(3);
subplot(3,2,1);
plot(t,demod1);plot(t,demod1,'y','linewidth',2)
xlabel('time');
ylabel('Amplitude');
title('demodulated Signal1 with 45deg');
f_demod1=abs((fft(demod1,1024)));
f_demod1=[f_demod1(514:1024) f_demod1(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,2);
plot(f,f_demod1,'y','linewidth',2)
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of Demodulated Signal1 with 45deg');
 
 
%----------------------2nd phase deviation--------------
 
XC2=Ac*cos((2*pi*fc*t)+90);
demod2=XC2.*sam;
subplot(3,2,3);
plot(t,demod2,'y','linewidth',2)
xlabel('time');
ylabel('Amplitude');
title(' demodulated Signal2 with 90deg');
f_demod2=abs((fft(demod1,1024)));
f_demod2=[f_demod2(514:1024) f_demod2(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,4);
plot(f,f_demod2,'y','linewidth',2)
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of demodulated Signal2 with 90deg');
 
 
%----------------------3rd phase deviation--------------
 
XC3=Ac*cos((2*pi*fc*t)+120);
demod3=XC3.*sam;
subplot(3,2,5);
plot(t,demod3,'y','linewidth',2)
xlabel('time');
ylabel('Amplitude');
title(' demodulated Signal3 with 120deg');
f_demod3=abs((fft(demod1,1024)));
f_demod3=[f_demod3(514:1024) f_demod3(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,6);
plot(f,f_demod3,'y','linewidth',2)
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of demodulated Signal3 with 120deg');
 
%----------------------1st frequency deviation--------------
 
XC4=Ac*cos(2*pi*(fc+500)*t);
demod4=XC4.*sam;
figure(4);
subplot(3,2,1);
plot(t,demod4);
xlabel('time');
ylabel('Amplitude');
title(' Amplitude demodulated Signal4freq deviation 500hz');
f_demod4=abs((fft(demod4,1024)));
f_demod4=[f_demod4(514:1024) f_demod4(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,2);
plot(f,f_demod4);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of demodulated Signal4 of freq deviation 500hz');
 
%----------------------2nd frequency deviation--------------
 
XC5=Ac*cos(2*pi*(fc+1000)*t);
demod5=XC5.*sam;
subplot(3,2,3);
plot(t,demod5);
xlabel('time');
ylabel('Amplitude');
title(' Amplitude demodulated Signal5 freq deviation 1000hz');
f_demod5=abs((fft(demod5,1024)));
f_demod5=[f_demod5(514:1024) f_demod5(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,4);
plot(f,f_demod5);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of demodulated Signal5 freq deviation 1000hz');
 
 
 
%----------------------3rd frequency deviation--------------
XC6=Ac*cos(2*pi*(fc+1500)*t);
demod6=XC6.*sam;
subplot(3,2,5);
plot(t,demod6);
xlabel('time');
ylabel('Amplitude');
title(' Amplitude demodulated Signal6 freq deviation 1500hz');
f_demod6=abs((fft(demod6,1024)));
f_demod6=[f_demod6(514:1024) f_demod6(1:513)];
f=(-511*fs/1024):(fs/1024):(512*fs/1024);
subplot(3,2,6);
plot(f,f_demod6);
xlabel('Frequency in Hz');
ylabel('Amplitude');
title('Spectrum of demodulated Signal6 freq deviation 1500hz');
 
 
%-----------------1st phase error demodulation using filter-------------
F=1000;s=15000;
x1=demod1;
[b,a] = butter(3,F*2/s,'low');
y1 = filtfilt(b,a,x1);
figure(5);
subplot(3,2,1)
plot(t,y1)
title('Demodulated Signal1 with phase deviaton 45degrees');
xlabel('Time');
ylabel('amplitude');
 
%-----------------2nd phase error demodulation using filter-------------
 
x2=demod2;
[b,a] = butter(3,F*2/s,'low');
y2 = filtfilt(b,a,x2);
subplot(3,2,2)
plot(t,y2)
title('Demodulated Signal2 with phase deviaton 90degrees');
xlabel('Time'); ylabel('amplitude');
%-----------------3rd phase error demodulation using filter-------------
 
x3=demod3;
[b,a] = butter(3,F*2/s,'low');
y3 = filtfilt(b,a,x3);
subplot(3,2,3)
plot(t,y3)
title('Demodulated Signal3 with phase deviaton 120degrees');
xlabel('Time'); ylabel('amplitude');
 
%---------------frequency error demodulation using filter-------
x6=demod6;
axis([0 0.005 -1 1])
[b,a] = butter(3,F*2/s,'low');
y6 = filtfilt(b,a,x6);
subplot(3,2,6);
plot(t,y6);
title('Demodulated Signal1 with freq deviation 500hz');
xlabel('Time'); ylabel('amplitude');
 
x5=demod5;
[b,a] = butter(3,F*2/s,'low');
y5 = filtfilt(b,a,x6);
subplot(3,2,5);
plot(t,y5);
title('Demodulated Signal with freq deviation 1000hz');
xlabel('Time'); ylabel('amplitude');
 
x4=demod4;
[b,a] = butter(3,F*2/s,'low');
y4 = filtfilt(b,a,x4);
subplot(3,2,4);
plot(t,y4);
title('Demodulated Signal with freq deviation 1500hz');
xlabel('Time'); ylabel('amplitude');

Tuesday, 5 August 2014

MATLAB code for DSB-SC modulation

fc=167000;
fm=fc/100;
fs=100*fc;
t=0:1/fs:4/fm;
xc=cos(2*pi*fc*t);
xm1=2*cos(1000*pi*t)-sin(1500*pi*t);
xm2=1.5*cos(2000*pi*t);
xm=xm1+xm2;
figure(1)
subplot(3,1,1),plot(t,xm1);
title('mesaage signal 1');
xlabel('time (sec)');
ylabel('amplitude');
subplot(3,1,2),plot(t,xm2);
title('message signal 2');
xlabel('time (sec)');
ylabel('amplitude');
subplot(3,1,3),plot(t,xm);
title('total message signal');
xlabel('time (sec)');
ylabel('amplitude')
% DSB-SC MODULATION
z1= xm.*xc;
figure(2)
subplot(2,1,1),plot(t,z1);
title('DSB-SC MODULATION IN TIME DAOMAIN');
xlabel('time (sec)');
ylabel('amplitude');
l1=length(z1);
f=linspace(-fs/2,fs/2,l1);
Z1=fftshift(fft(z1,l1)/l1);
subplot(2,1,2),plot(f,abs(Z1));
title('DSB SC MODULATION IN FREQUENCY DOMAIN');
xlabel('frequency(hz)');
ylabel('amplitude');
demodulation
s1=z1.*xc;
S1=fftshift(fft(s1,length(s1))/length(s1));
figure(3)
plot(f,abs(S1));
title(' demodulated signal IN FREQUENCY DOMAIN before filtring');
xlabel('frequency(hz)');
ylabel('amplitude');

For information about DSB-SC modulation:
http://en.wikipedia.org/wiki/Double-sideband_suppressed-carrier_transmission


Wednesday, 30 July 2014

plz like this page in facebook,this page let world know about the problems faced by people of  Nalgonda due to excess fluorosis present in the water. So by viewing this page on facebook, government would come to know about problems faced by them and also these villages might get some funds to become free from that devil fluoride. https://www.facebook.com/pages/Fluoride-Nalgonda/344490329038536?ref=hl

Tuesday, 29 July 2014

Automatic bed light using NE555.(NI My Daq simulations are included)

This main components used in this circuit are Light dependent Resistor(LDR), NE555, and an LED.
The principle in this circuit is when the  light from tubelight falls on the LDR resistance of LDR is very less  and +Vcc  is appeared at the second pin of 555 which is operated in monostable mode. So as +Vcc appears at pin 2 then the output of the 555 is zero (Why output is zero?  for more information about 555 see this link).  When tubelight is switched off light does not fall on the LDR so  LDR offers high resistance so now at pin 2 it is grounded , so the output is one (in terms of Boolean).Note that this circuit is kept near tubelight where more light is falling on it and also more light due to daylight in the morning.

Output:When light is not falling on the LDR i.e.,LED is glowed .





Output of NI My Daq when light is not falling on the LDR.
Output:When light is falling on LDR.(LED is not glowing)
Output of NI My Daq during light is falling on LDR.

Wednesday, 23 July 2014

RPM Counter using 555 timer (Multisim and NI MyDaQ simulation Results included)


This circuit is an RPM counter. The main aim of this circuit is to count no.of rotations made in a minute by a simple wheel. This circuit is divided into 3 parts: 
1) Sensing of the rotations
2) generating the pulse signals
3) Display on the LCD


The circuit makes use of simple Monstable multivibrator[1] operation. It uses IC 555, capacitors, resistors and a battery. When the trigger input is low, then the output remains high. When the trigger is high, output remains low. The triggering is changed in this circuit by the help of a photo transistor. Let us consider a holed rotor all along its periphery. When the light falls on it, it acts as a short circuit and triggering is made low as it is grounded. Then the output is high. When the light is blocked by opaque part of rotor, the trigger is voltage divided from +VCC. Thus output remains low. Whenever hole comes, light falls on transistor and based upon this the output pulses are generated.
Again to make 5 pulses for 5 holes as one pulse, we use another similar multivibrator circuit by changing the width of the pulse by changing the resistance of second 555 multivibrator.

The display is done by Seven Segment display. To know about seven segment display, see this link[2].
Now we get number of cycles per second.We can calibrate it for Rotations Per Minute (RPM).Multiply the output from multivibrator-2 by a factor 60 by placing a multiplier (using an op-amp).After this give it to Seven Segment Display. 

Simulated circuit is below:

We can compare output of one multivibrator to output of the other.






Testing in myDAQ:

This circuit counts only single digit RPM. The same circuit can be further extended to count more RPM by making manipulations in seven segment display ( by increasing the number of seven segment displays) to know about how to increase the number of digits from one to two and more etc  see this link[3] .
References: