Engineers Garage

  • Electronic Projects & Tutorials
    • Electronic Projects
      • Arduino Projects
      • AVR
      • Raspberry pi
      • ESP8266
      • BeagleBone
      • 8051 Microcontroller
      • ARM
      • PIC Microcontroller
      • STM32
    • Tutorials
      • Audio Electronics
      • Battery Management
      • Brainwave
      • Electric Vehicles
      • EMI/EMC/RFI
      • Hardware Filters
      • IoT tutorials
      • Power Tutorials
      • Python
      • Sensors
      • USB
      • VHDL
    • Circuit Design
    • Project Videos
    • Components
  • Articles
    • Tech Articles
    • Insight
    • Invention Stories
    • How to
    • What Is
  • News
    • Electronic Product News
    • Business News
    • Company/Start-up News
    • DIY Reviews
    • Guest Post
  • Forums
    • EDABoard.com
    • Electro-Tech-Online
    • EG Forum Archive
  • DigiKey Store
    • Cables, Wires
    • Connectors, Interconnect
    • Discrete
    • Electromechanical
    • Embedded Computers
    • Enclosures, Hardware, Office
    • Integrated Circuits (ICs)
    • Isolators
    • LED/Optoelectronics
    • Passive
    • Power, Circuit Protection
    • Programmers
    • RF, Wireless
    • Semiconductors
    • Sensors, Transducers
    • Test Products
    • Tools
  • Learn
    • eBooks/Tech Tips
    • Design Guides
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • Digital Issues
    • EE Training Days
    • LEAP Awards
    • Podcasts
    • Webinars / Digital Events
    • White Papers
    • Engineering Diversity & Inclusion
    • DesignFast
  • Guest Post Guidelines
  • Advertise
  • Subscribe

DIY : Short Range Optical Pulse Transmitter and Receiver

By Ashutosh Bhatt September 24, 2014

This project demonstrates how pulses can be transmitted from one place to another place wirelessly using light as medium. One LED is connected at the transmitter side that blinks at frequency of applied pulses. At the receiver side, Light Dependent Resistor (LDR) is used to receive light pulses. IC555 is used at both ends. At transmitter side it is used to generate continuous pulses with variable frequency output from 1 Hz to 10 Hz.  At receiver side it is used to generate same pulses as per the trigger input applied by LDR.   

Note – for visual effect (demonstration) the pulse frequency is kept low. The frequency can be kept high in terms of KHz also.


Transmitter

IC555 is connected in astable mode to generate continuous pulses. The max and min pulse frequencies are calculated as

Fmin        = 1.44 / (R1 + 2×(R2+R3max))×C1

Substituting values as per the circuit diagram 

                                                            = 1.44 / (4700 + 2×(4700+50000)×10×10-6

                                                            = 1.2 Hz

Similarly

Fmax       = 1.44 / (R1 + 2×(R2+R3min))×C1

                                                            = 1.44 / (4700+2×(4700+0)) ×10×10-6

                                                                                 = 10.2 Hz

These pulses are applied to super bright white LED. So it will blink at a rate of 1 Hz to 10 Hz.

Receiver – IC555 is connected in monostable mode. R5 and C3 are timing components. So output pulse time is

                                                            T = 1.1×R5×C3

As per given values

                                                             = 1.1×1000×0.1×10-6

                                                                                 = 1.1×10-4

 = 0.11 ms

That means output pulse time is very short and it tries to follow applied trigger input – which means till the time trigger input is low, the output remains high.

The LDR with 10K resistor is connected in such a way that when light pulse falls on it – it gives trigger pulse to IC555. The required triggering voltage for IC555 is Vcc / 3. If voltage at pin no 2 of IC555 is more than Vcc/3 then no trigger. But as the voltage falls below Vcc/3, the trigger is applied and output goes high.

Let us see how this happens.

In the room light the LDR resistance is 15K. When strong light (like light of super bright LED) directly falls on it, its resistance decreases to 1K. So in the room light when the LDR resistance is 15K the trigger voltage Vt is

Vt = (LDR / R6+LDR)×Vcc

                                                    = (15 / 15+10) ×Vcc

                                                    = 3/5 Vcc > Vcc / 3

So in room light IC555 does not get any trigger from LDR. But as light pulse from LED falls on it its resistance decreases to 1K. So the trigger voltage will be

Vt = (1 / 1+10) ×Vcc

                                                    = Vcc / 11 << Vcc / 3

So IC555 gets the trigger and its output goes high and remains high till the duration of light pulse. So the LED at receiving side also blinks at the same rate of transmitter LED.

Circuit Operation

·         First supply is given to the receiver because no direct light is falling on LDR, the receiver output is low and receiver LED is off

·         Next when the supply is given to the transmitter, the LED starts blinking

·         The transmitter LED is pointed towards LDR

·         So the LDR receives direct light and it generates trigger pulse to IC555

·         IC555 gives high output till the duration of the light pulse

·         So the transmitter LED and receiver LED blinks at the same rate with same frequency

·         As the blinking rate of transmitter LED is varied using pot R3, the blinking rate of receiver LED also changes

Circuit Diagrams

CIRCUIT-DIAGRAM_1

Project Components

  • 555 Timer IC
  • LDR
  • LED
  • Potentiometer
  • Resistor

Project Video


Filed Under: 555 Timers, Electronic Projects
Tagged With: 555 timer circuit, 555 timer IC, ldr, optical pulse transmitter
 

Next Article

← Previous Article
Next Article →

Questions related to this article?
👉Ask and discuss on Electro-Tech-Online.com and EDAboard.com forums.



Tell Us What You Think!! Cancel reply

You must be logged in to post a comment.

EE TECH TOOLBOX

“ee
Tech Toolbox: Internet of Things
Explore practical strategies for minimizing attack surfaces, managing memory efficiently, and securing firmware. Download now to ensure your IoT implementations remain secure, efficient, and future-ready.

EE Learning Center

EE Learning Center
“engineers
EXPAND YOUR KNOWLEDGE AND STAY CONNECTED
Get the latest info on technologies, tools and strategies for EE professionals.

HAVE A QUESTION?

Have a technical question about an article or other engineering questions? Check out our engineering forums EDABoard.com and Electro-Tech-Online.com where you can get those questions asked and answered by your peers!


RSS EDABOARD.com Discussions

  • ADS optimization cockpit window does not open
  • Voltage mode pushpull is a nonsense SMPS?
  • Will this TL084C based current clamp circuit work?
  • How to determine the maximum PAD frequency ?
  • Xiaomi Mijia 1C Robot problem of going backwards while working

RSS Electro-Tech-Online.com Discussions

  • Siemens large industrial PLC parts
  • Parts required for a personal project
  • Cant log in to Easy PC forum
  • Failure of polypropylene motor-run capacitors
  • Wideband matching an electrically short bowtie antenna; 50 ohm, 434 MHz

Featured – RPi Python Programming (27 Part)

  • RPi Python Programming 21: The SIM900A AT commands
  • RPi Python Programming 22: Calls & SMS using a SIM900A GSM-GPRS modem
  • RPi Python Programming 23: Interfacing a NEO-6MV2 GPS module with Raspberry Pi
  • RPi Python Programming 24: I2C explained
  • RPi Python Programming 25 – Synchronous serial communication in Raspberry Pi using I2C protocol
  • RPi Python Programming 26 – Interfacing ADXL345 accelerometer sensor with Raspberry Pi

Recent Articles

  • AC-DC power supply extends voltage range to 800 V DC
  • Infineon’s inductive sensor integrates coil system driver, signal conditioning circuits and DSP
  • Arm Cortex-M23 MCU delivers 87.5 µA/MHz active mode
  • STMicroelectronics releases automotive amplifiers with in-play open-load detection
  • Convection-cooled power controller integrates EtherCat connectivity

EE ENGINEERING TRAINING DAYS

engineering

Submit a Guest Post

submit a guest post
Engineers Garage
  • Analog IC TIps
  • Connector Tips
  • Battery Power Tips
  • DesignFast
  • EDABoard Forums
  • EE World Online
  • Electro-Tech-Online Forums
  • EV Engineering
  • Microcontroller Tips
  • Power Electronic Tips
  • Sensor Tips
  • Test and Measurement Tips
  • 5G Technology World
  • Subscribe to our newsletter
  • About Us
  • Contact Us
  • Advertise

Copyright © 2025 WTWH Media LLC. All Rights Reserved. The material on this site may not be reproduced, distributed, transmitted, cached or otherwise used, except with the prior written permission of WTWH Media
Privacy Policy

Search Engineers Garage

  • Electronic Projects & Tutorials
    • Electronic Projects
      • Arduino Projects
      • AVR
      • Raspberry pi
      • ESP8266
      • BeagleBone
      • 8051 Microcontroller
      • ARM
      • PIC Microcontroller
      • STM32
    • Tutorials
      • Audio Electronics
      • Battery Management
      • Brainwave
      • Electric Vehicles
      • EMI/EMC/RFI
      • Hardware Filters
      • IoT tutorials
      • Power Tutorials
      • Python
      • Sensors
      • USB
      • VHDL
    • Circuit Design
    • Project Videos
    • Components
  • Articles
    • Tech Articles
    • Insight
    • Invention Stories
    • How to
    • What Is
  • News
    • Electronic Product News
    • Business News
    • Company/Start-up News
    • DIY Reviews
    • Guest Post
  • Forums
    • EDABoard.com
    • Electro-Tech-Online
    • EG Forum Archive
  • DigiKey Store
    • Cables, Wires
    • Connectors, Interconnect
    • Discrete
    • Electromechanical
    • Embedded Computers
    • Enclosures, Hardware, Office
    • Integrated Circuits (ICs)
    • Isolators
    • LED/Optoelectronics
    • Passive
    • Power, Circuit Protection
    • Programmers
    • RF, Wireless
    • Semiconductors
    • Sensors, Transducers
    • Test Products
    • Tools
  • Learn
    • eBooks/Tech Tips
    • Design Guides
    • Learning Center
    • Tech Toolboxes
    • Webinars & Digital Events
  • Resources
    • Digital Issues
    • EE Training Days
    • LEAP Awards
    • Podcasts
    • Webinars / Digital Events
    • White Papers
    • Engineering Diversity & Inclusion
    • DesignFast
  • Guest Post Guidelines
  • Advertise
  • Subscribe