1. Author:-
IKJOT SINGH
MOHIT LAMBA
LDR CAMERA
A non conventional design
This is a low budget device. Use it as a camera, use it as a
touchpad or simply control your computer with your gestures.It
can be used as one like .

2. LDR CAMERA 1
Motivation
A WORKSHOP AT IIT DELHI
On 12th
January 2015, both of us attended a workshop in IIT Delhi, organized by
Texas instruments (TI) in Bharti building under Dr. C. P. Ravikumar
.there one of the presenter Mr. Mukul Bhanwar showed us, how a conventional
camera pixel is designed and fabricated by using diodes and other components.
He then went on to show us his first camera that he himself has designed in TI,
which was of 128x128 matrix of such pixels. We were simply amazed.
A SEMINAR IN OUR OWN COLLEGE
Back in our college, one month later, I was taking a seminar on ‘Digital Image
Processing (DIP)’ under IEEE. While demonstrating of how powerful tool
MATLAB is in DIP, especially its power of converting matrices into images and
vice versa, one of the student, IKJOT SINGH came up with a very bizarre idea.
IKJOT SINGH recalled that one can vary easily the voltage in a circuit as a
function of intensity of light falling on it, simply with the help of a Light Dependent
Resistor (LDR). He further argued if we take a matrix of LDR ( a similar thing that
has been done by Mukul Sir in IIT Delhi) then the values returned by each LDR
in that matrix can be treated as a pixel value of an image.

3. LDR CAMERA 2
The Concept
An image can be of class uint8, uint16, single, or double. Each pixel color is of a
value between 0 and 1 as depicted below.
A pixel whose pixel color is 0 is displayed as black, and a pixel whose color
components pixel color is 1 is displayed as white.
The setup of our project is as follows. In between a light source and an object
there will be a LDR matrix. This LDR should be as big as possible for best
results. However for our experimentation we have restricted it to a 10x10 matrix.
Now the voltage developed across each LDR is fed to an Analog to Digital
Convertor (ADC). This ADC is further connected to a computer, via shift register,
so that the MATLAB can use these values. However to simplify our task specially
when it comes to serial communication we decided to use an Arduino in place of
the ADC.

4. LDR CAMERA 3
Figure 1: Concept Diagram

5. LDR CAMERA 4
Hardware Required
Following hardware is required:-
 LDR (100 pc)
 1N4007 Diodes (100 pc)
 Dotted PCB (1)
 Arduino (1)
 Bug strips
 Connecting wire
 Bug strips connectors
 Soldering Iron and Soldering wires
Figure 2: Hardware Required

6. LDR CAMERA 5
Circuit Diagram
Following is the circuit taken from Mathworks documentation, a link to this has
been given in the references.
Here a 5V supply is used to power the circuit. Now as light intensity falling on the
LDR varies the resistance of the LDR varies. This variation in LDR resistance
causes a change in voltage drop across the 10 KΩ resistor. Now this voltage
difference is read by ADC.
Now to simplify our task especially to do away with the serial communication
problem, we decided to use an Arduino instead. Arduino has a predefined library
file for interfacing with MATLAB. A link to learn this interfacing has also been
provided in the references.
Figure 3: Test Circuit

7. LDR CAMERA 6
Next is the circuit diagram that we used for designing the circuit for our LDR
Camera. For sake of simplicity we initially considered only a 3 x 3 matrix.
The multiplexing used here is very similar to LED multiplexing.
When a particular column is set high and a particular row goes low, the circuit is
completed for the LDR present at their intersection. All the rest column are kept
low and similarly all the rest rows are kept high. Any other LDR other than the
selected one will be open circuited because the corresponding diode will be
reverse biased. All these column and rows pins are connected to the DIGITAL
PINS of Arduino. The reading across the 10 KΩ resistor is taken by the ANALOG
PIN of Arduino as shown in figure.
Now one can extend this circuit to a MxN matrix (here we have used a 10x10
matrix).
Figure 4: Prototype Circuit

8. LDR CAMERA 7
Finished device
Figure 5: Front side view
Figure 6: Back side view

9. LDR CAMERA 8
Figure 7: Complete circuit

10. LDR CAMERA 9
Testing
After making this hardware we just wanted to test the variations across a single
LDR just to check our connections. In this code we are not Multiplexing the
entire matrix but just concentrating on a single LDR. This is our code in MATLAB
for testing.
This code was repeated arbitrarily for 5 to 6 LDR in our matrix.
clc
clear all
a= arduno('COM5');
%creating arduino object in matlab
pinMode(a,41,'output'); %column pin
pinMode(a,40,'output'); %row pin
pinMode(a,3,'input'); %analog read
pin
digitalWrite(a,41,1); %column pin set
high
digitalWrite(a,40,0); %row pin set
low
i=0;
while(i<20)
val=analogRead(a,3);
val
pause(.5)
end

11. LDR CAMERA 10
Code
Here is our actual code for the device.
clc;
clear all;
a=arduino('COM3')
for k=13:22
pinMode(a,2*k,'OUTPUT');
digitalWrite(a,2*k,1);
pinMode(a,(2*k+1),'OUTPUT');
digitalWrite(a,(2*k+1),0);
end
pic=zeros(10,10);
for i=1:30
val(:,:,i)=zeros(10,10);
count=1;
for k=13:22
digitalWrite(a,2*k,0);
for j=13:22
digitalWrite(a,(2*j+1),1);
pic(count)=analogRead(a,k-13);
count=count+1;
digitalWrite(a,(2*j+1),0);
end
digitalWrite(a,2*k,1);
end
pic'
pic=mat2gray(pic');
val(:,:,i)=pic;
figure(i),imshow(val(:,:,i));
end

12. LDR CAMERA 11
In the following video we were moving our thumb over the LDR matrix. As we
moved our thumb following is the sequence of images captured by MATLAB
using the LDR matrix.

13. LDR CAMERA 12
References
1. To learn how to interface MATLAB and Arduino we referred this link.
http://www.instructables.com/id/Tutorial-6-MATLAB-and-Arduino-
part-1-up-and-run/
2. To learn how a single LDR is interfaced with MATLAB, refer to this link.
http://in.mathworks.com/matlabcentral/fileexchange/47605-creating-a-
motion-detector-using-an-arduino--a-photoresistor-and-
matlab/content/html/Photoresistor_Motion_Detection_Article.html
Figure-2 of our documentation was taken from this link.
3. For learning Digital Image Processing refer to the following books
a. Title : Digital Image Processing (English) 3rd Edition
Author : Richard E Woods, Rafael C Gonzalez
Publisher : Pearson
ISBN-10 : 8131726959
b. Title : Digital Image Processing using Matlab
Author : Richard E Woods, Rafael C Gonzalez,Steven L. Eddins
Publisher : McGraw Hill Education (India) Private Limited
ISBN-10 : 0070702624
4. To learn Arduino refer to this ebook
http://www.nfiautomation.org/FREE_Download/Technical%20Documen
ts/Arduino/30%20arduino%20projects%20for%20the%20evil%20genius.
pdf