Temperature control system circuit design based on ATmega16L microcontroller

Introduction: Design a temperature control system based on ATmega16L microcontroller, and explain the hardware design of the system. Adopt modular design method and use incremental PID algorithm to make the temperature value of the controlled object tend to the given value.

main controller

The main controller of the system adopts ATmega16L, which is a high-performance, low-power 8-bit AVR microprocessor with advanced RISC structure, large-capacity ROM, RAM, Flash and EEPROM, integrated 4-channel PWM, SPI serial peripheral interface, and 8-way 10-bit A/D converter. For the data acquisition system, no separate A/D converter is required, which can save costs. In addition, the microcontroller provides a JTAG debugging interface, and a self-made simple JTAG emulator can be used for program debugging.

Temperature acquisition circuit

The figure shows the temperature acquisition circuit. The circuit is mainly composed of the temperature sensor AD590 and the differential operational amplifier AD524. The temperature sensor AD590 is a new type of two-terminal constant current device. The excitation voltage range is 4 to 30 V, and the temperature measurement range is -55 to +150°C. When the current of AD590 flows through a 5 kΩ resistor, the temperature rises by 1 K, and the voltage on the resistor increases by 5 mV, which is converted to 5 mV/K. Therefore, when the temperature changes between 0 and 100°C, the resistor voltage changes between 1.365 and 1.865 V. The operational amplifier AD524 is used to convert absolute temperature into Celsius temperature.

Temperature control circuit

The circuit is mainly composed of a photocoupler and a thyristor, as shown in the figure. The control signal (PWM) sent by the microcontroller controls the working state of the photocoupler after passing through the driver. When the photocoupler works, the trigger pole of the bidirectional thyristor is at a high level, and the thyristor is in the on state, thereby controlling the operation of the heating rod.