Distance Approximation Using IR LED, IR Receiver Photodiode And OpAmp

This project shows a simple way to estimate an object's distance using an infrared LED and a photodiode. It works by detecting the change in reflected infrared light, allowing us to gauge how near or far the object is. An OP-AMP is set up as a comparator to control LEDs, giving a visual cue of the distance.

Sub Executive, Fall2023, RND Team - AUST Robotics Club

Student | Department of Electrical & Electronic Engineering, AHSANULLAH UNIVERSITY OF SCIENCE AND TECHNOLOGY

An operational amplifier (OP-AMP) is a versatile electronic component used to amplify voltage signals. In this project, the OP-AMP acts as a comparator, comparing the input signal from the sensor to a reference voltage and producing an output based on the comparison. Its output is used to control other components, like LED, depending on whether the input voltage is higher or lower than the reference. Learn more

Pin configuaration and function of an OP-Amp

Pin configuration and function of an OP-Amp

Infrared transmitter diode (IR333C):

An infrared emitter is a source of light energy in the infrared spectrum. It is a light emitting diode (LED) that is used in order to transmit infrared signals from a remote control. Learn more

Infrared receiver diode (PD333-3B):

IR receiver diodes are used in object detection applications like line follower, obstacle detecting robots etc. along with IR emitter. Learn more

Setup And Operational Guide

Now that we’ve covered the basics of Op-amps and sensors, let’s look at the components you’ll need for this project.

Components for this project

1. Resistors (220Ω, 540Ω, 1kΩ, 10kΩ)

2. OP-AMP (UA741CP)

3. Infrared transmitter diode (IR333C)

4. Infrared receiver diode or photo-diode (PD333-3B)

5. LED (Green, Yellow, Red)

6. 9V DC Battery

7. Breadboard

8. Wires

Circuit Setup

Simulation Circuit of object distance detector circuit designed in tinkercad

Simulation circuit setup of object distance detector - circuit designed in Tinkercad

Object distance detector circuit diagram

Object distance detector circuit schematic

Actual Circuit Setup of Simulation object distance detector

How does the circuit work?

In the IR sensor circuit branch the resistors have been set in a way that maximum 8-8.5V can be obtained depending on the distance of the object from the IR emitter. The sensor circuit gives output voltage, Vr, depending on the distance from the object. It is to be noted that the closer the object the lesser the output voltage (Vr) will be obtained.

Three op-amps are biased with two distinct 9V batteries. The pin-3 (V+ pin) of the three op-amps was given three different input voltages from a 9V battery using a branch of resistors. Experimentally, Va = 7.4V, Vb = 5.1V, Vc = 2.5V. The op-amps are operated in comparator mode and compared with the various output voltages from the IR sensor circuit, Vr. Lastly the op-amps are connected to LEDs, so that saturation voltages illuminate the LED depending on the input voltage, Vr.

Now,

Va > Vb > Vc
If Vr > Va, two LEDs will be ‘on’, indicating maximum distance.
If Vr > Vb, three LEDs will be ‘on’, indicating medium distance.
If Vr > Vc, four LEDs will be ‘on’, indicating minimal distance.

Useful Information

The circuit was tested with different object distances, and the voltage readings from the photo-diode and OP-AMP outputs were recorded.

Table-1: Voltage reading from op-amp V+ (pin-3)

Table-2: Voltage for different distance from infrared LED

Troubleshooting

1. The sensor circuit was experimented with various resistors combinations to obtain the maximum voltage without crossing the rated voltages of the LEDs.

2. The op-amp model used had some issue where if negative biasing was not given, it gave a continuous positive output which introduces error. To solve this another 9V battery was used for negative biasing and the circuit was changed accordingly.

Summary

In electronics and robotics object detection and distance detection using infrared (IR) sensors are common applications. Basic circuit includes IR sensors and comparator. Sometimes amplification is also required to determine a wide range of distance. The infrared sensor basically sends and receives light energy as signals, these signals later converted to electrical signals to analyze and compare. These sensors are versatile and with proper implementation can be integrated into various projects to enhance functionality and automation.