Temperature-controlled switches serve as critical automation components across industrial, agricultural, medical, and domestic applications. From manufacturing temperature monitoring to greenhouse climate management and medical equipment regulation, these systems play vital roles.

Traditional mechanical switches often suffer from low precision, slow response times, and mechanical wear. Electronic alternatives offer superior accuracy, faster response, and longer lifespans, making them increasingly prevalent. However, designing high-performance electronic switches requires careful consideration of multiple factors including sensor selection, circuit design, relay operation, and power stability. Achieving precise calibration and robust interference resistance present additional technical challenges.

The system comprises three core components: temperature sensing, control processing, and relay activation modules. Operational workflow follows these stages:

1. Temperature Sensing: The LM35 sensor converts ambient temperature to voltage (10mV/°C)
2. Signal Processing: An LM358 operational amplifier compares sensor output against preset reference voltages
3. Threshold Logic: Outputs high/low signals based on temperature comparisons
4. Relay Activation: Transistor T1 amplifies control signals to operate relay RL1
5. Load Control: Relay contacts manage external devices like fans or lighting systems

A stabilized 5V DC power supply is achieved through:

• Transformer X1 (230V AC to 9V AC conversion)
• Bridge rectifier BR1 for AC-DC conversion
• Filter capacitor C1 (1000μF) for ripple reduction
• LM7805 voltage regulator for stable 5V output
• LED1 for power status indication

The LM35 precision IC sensor offers:

• ±0.5°C accuracy
• Linear 10mV/°C output
• Low power consumption (<60μA)
• Direct ADC compatibility

The LM358 dual op-amp configured as comparator provides:

• Single-supply operation (3-32V)
• Low power consumption
• High gain characteristics
• Adjustable thresholds via potentiometer RP1

Key components include:

• NPN transistor T1 for signal amplification
• Relay RL1 for load switching
• Protection diode D1 for voltage spike suppression

The system requires precise calibration using standard temperature references. Threshold adjustment involves:

1. Determining target control temperature
2. Calculating corresponding reference voltage
3. Adjusting RP1 potentiometer to match calculated values
4. Validating relay activation at target temperatures

Key evaluation metrics include:

• Control Accuracy: ±1°C tolerance
• Response Time: Under 5 seconds
• Operational Stability: 72+ hours continuous operation
• EMI Resistance: Stable performance in standard interference environments

Implementation scenarios include:

• Automated greenhouse climate control
• Precision incubation temperature regulation
• Home appliance temperature management
• Industrial equipment thermal protection

Potential system enhancements include:

• Advanced digital temperature sensors for improved precision
• PID control algorithms for enhanced stability
• Wireless connectivity for remote monitoring

Through continuous technical innovation, temperature control systems will assume increasingly critical roles in automation applications across diverse sectors.