SYS_MODULE // 03

Intruder Alert System

RF_SENS ANALOG_DSP OP_AMP

> Exec_Summary

This project was created in my Intro to ECSE course to explore potential interests within electrical engineering. The system utilizes a 40kHz ultrasonic sensor, an Arduino Uno, an LED, a relay, an Analog Discovery 2, and an op-amp to drive a speaker.

> Transmission_Logic

Ultrasonic sensors detect proximity by measuring the time it takes for a transmitted signal to reflect off an object and return, calculating the distance based on the speed of sound. The module consists of a transmitter, a receiver, and a control circuit.

The system works by transmitting eight 40kHz pulses and monitoring for a reflection. In the circuit, the microcontroller directly drives the ultrasonic transmitter.

> Receive_Chain_&_Amplification

[Image of LM324 op-amp circuit diagram]

The receiver's output must be carefully conditioned. The signal is isolated and amplified using an LM324 op-amp configured with an inverted gain of 9. This output passes through a bandpass filter to isolate the target 40kHz frequency. Finally, it is amplified once more with an inverted gain of ~16, yielding a theoretical total system gain of ~144.