This project demonstrates the design and simulation of an op-amp based alarm system using LTspice. The system detects input signals (simulating door/window sensors) and triggers an alarm using a comparator and transistor switching stage.
- The input signal is applied to the non-inverting terminal of the op-amp.
- A reference voltage is generated using a resistor divider network.
- The op-amp operates as a comparator.
- When the input voltage exceeds the reference voltage, the output switches HIGH.
- The output drives a PNP transistor, which acts as a switching device.
- The transistor activates the alarm (LED/load).
- Op-amp comparator operation
- Voltage divider for reference generation
- Transistor as a switching device
- Threshold-based detection
- Software: LTspice
- Input: Pulse signal
- Supply Voltage: 16V
- Analysis: Transient (.tran)
- Input: Pulse waveform
- Op-amp output: HIGH/LOW switching
- Alarm output: ON/OFF response
R. L. Boylestad and L. Nashelsky, Electronic Devices and Circuit Theory, 11th ed., Pearson, 2013.
- Door and window alarm systems
- Intruder detection systems
- Basic security circuits
Thangavikraman Ramachandran
B.E Electronics and Communication Engineering (Pre-final Year)
This project demonstrates practical analog circuit design and simulation using LTspice, focusing on comparator-based decision making and transistor switching behavior.