Senior Design Lab 2
Noise-Robust Infrared Light Curtain Receiver with Buzzer and SMS Alerts
Introduction
The goal of this lab was to create a receiver that would detect an infrared signal from a transmitter provided. This receiver must be robust in the presence of noise, such as sunlight or ambient light from incandescent bulbs. The receiver is meant to function like a “light curtain” in that it should detect if the infrared beam is broken. If the beam is broken, a buzzer should sound and an SMS alert should be sent to a hard-coded phone number.
Design Process
- Analyzed provided transmitter to determine characteristics of the infrared signal
- Inspected many operational amplifier (op amp) datasheets to design and create a 2nd order Butterworth high pass filter using a Sallen-Key topology
- Designed circuit layout with components incl. infrared phototransistor, buffer, filter, amplifier, and voltage regulator
- Read voltage output from the receiver using the analog-to-digital converter (ADC) in Arduino Uno with C++
- Implemented logic to detect beam obstruction using Arduino Uno C++
- Connected Arduino to a computer using serial USB, then used a Python script on computer to send SMS alerts
Figures
Figure 1: A high-level view of major subsystems
Figure 2: Schematic of circuit design
Figure 3: The complete receiver circuit