A temperature control system based on ATMEGA16L single chip microcomputer is designed, and the hardware design scheme of the system is described. Using modular design method and incremental PID algorithm, the temperature value of the controlled object tends to the given value.
The main controller of the system adopts ATMEGA16L. The single chip microcomputer is an 8-bit avr microprocessor with high performance and low power consumption. It has advanced RISC structure, large capacity ROM, ram, flash and EEPROM, integrated 4-channel PWM, SPI serial peripheral interface, and 8-channel 10 bit a / D converter. For the data acquisition system, there is no external a / D converter, This can save costs. In addition, the single chip microcomputer provides JTAG debugging interface, and the self-made simple JTAG simulator can be used for program debugging.
Temperature acquisition circuit
The figure shows the temperature acquisition circuit. The circuit is mainly composed of temperature sensor AD590 and differential operational amplifier AD524. Temperature sensor AD590 is a new two terminal constant current device. The excitation voltage range is 4 ~ 30 V, and the temperature measurement range is – 55 ~ + 150 ℃. When the current of AD590 flows through a 5 K Ω resistor, the temperature increases by 1 K, and the voltage on the resistor increases by 5 mV, that is, it is converted to 5 mV / K. Therefore, when the temperature changes between 0 and 100 ℃, the resistance voltage changes between 1.365 and 1.865 v. The operational amplifier AD524 is used to convert the absolute temperature into Celsius.
Temperature control circuit
The circuit is mainly composed of optocoupler and thyristor, as shown in the figure. The control signal (PWM) sent by the single chip microcomputer controls the working state of the optocoupler after passing through the driver. When the optocoupler works, the trigger electrode of the bidirectional thyristor is at the high level, and the thyristor is in the on state, so as to control the operation of the heating rod.