Light Detector

In this project, we will build a light detector circuit using a NAND gate chip.

A light detector circuit is a circuit that can detect light.

When a bright light shines on the circuit, such as from a flashlight, the LED will turn ON.

1. Presentation
on
Light Detector
Dhaka International University
Date: 06-08-2017

2. Dhaka International University
Presented By-
1
Sl No Name Roll
1 Al- Imran 07
2 Md. Sahabuddin 08
3 Md. Arif Hossain 33
4 Bokul Ahmed 39
Department of EETE
Batch: 31
st
(eve)
Sem: 6
th

3. Content
 Objective of this Project
 What is Light Detector?
 Truth Table of NAND Gate
 Schematic diagram of the light detector
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 How Light Detector circuit works?

4.  Objective of this Project
 In this project, we will build a light detector
circuit using a NAND gate chip.
Dhaka International University
3

5. What is Light Detector?
 A light detector circuit is a circuit that can detect
light.
 When a bright light shines on the circuit, such as
from a flashlight, the LED will turn ON.
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6.  Truth Table of NAND Gate
 Each NAND gate has input pins and 1 output pin.
The following chart shows NAND gate logic, which shows
what output a NAND gate chip will produce for a set of
given inputs:
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7. Dhaka International University
Component Needed for light Detector:
6
Sl No Components Name Quantity
1 Bread Board 1 Pcs
2 IC (74#C00) 1 Pcs
3 LDR 1 Pcs
4 Resistor (6.8 KΩ & 330 Ω)1+1= 2 Pcs
5 LED 1 Pcs
6 Battery (5v) 1 Pcs
7 Jumper Wire Quantitatively

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 Schematic diagram of the light detector
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9.  How Light Detector circuit works?
•For this Circuit we use a voltage divider as an
Input of NAND gate.
•When a photoresistor is exposed to darkness,
it has very high resistance for this resistance
All the voltage will pass through the 6.8 K resistor
as a result NAND gate input will be High that means
‘1’ and as the NAND gate input is short
So basically it will get its input (1 1). So from the
Truth Table of NAND gate it means the output
will be ‘0’
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10.  How Light Detector circuit works? (Cont)
•Again when a photoresistor is exposed to
brightness it’s resistance will drop dramatically.
So the voltage will fall half across the
photoresistor. For this the NAND gate Input will
gate ‘0’. From truth table we will gate the output
as high. That means ‘1’
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11. Team Work

12. Finally we did it

13. Dhaka International University

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