Application and characteristics of CNC DC power supply
This project studies the design of an intelligent, high-precision, and simple CNC DC power supply with a microcontroller as the core. Numerical control DC power supply is a common electronic instrument and one of the commonly used devices in electronic technology, widely used in fields such as circuits, teaching experiments, and scientific research. A new generation of CNC DC power supply designed with a microcontroller system as its core. It not only has a simple circuit, compact structure, low price, and superior performance, but also has the ability to calculate and control data using microcontrollers, which can eliminate and reduce errors caused by analog circuits. The output voltage and limited current are input through a keyboard. The appearance of the power supply is beautiful, easy to operate, and has high value. It also has dual overload protection and alarm functions, making it particularly suitable for various high-precision applications.
Design of hardware circuits
The composition of a CNC DC power supply is simple. The CNC DC power supply consists of five parts: a stabilized power supply part, a digital display part, an output part, a CNC part, and "+" and "-" buttons.
Design of Unit Circuit
The output circuit is composed of a three terminal fixed output regulator 7805, an operational amplifier A, and a DAC circuit. In this circuit, U23=5V, Uo=U23+U3. If the output of the DAC is -5V to+4.9V, then UO=0 to 9.9V. The voltage stabilization performance of this circuit is guaranteed to be 7805, and the step voltage is controlled by the digital input of the DAC. The accuracy of the output voltage of this circuit depends on the error of the 7805 output voltage; The tracking error of operational amplifiers and the integration nonlinearity of DACs. The error of the step value is directly related to the number of bits in the DAC.
The functions that the CNC part should have include: preset output voltage, and the ability to add (+) or subtract (-) in a "step" or "scan" working mode. The output of the numerical control part should directly control the various switches of the digital resistor network.
Microcontrollers (MCUs), also known as single-chip microcontrollers, refer to the numerical control circuit of the MCU. There are many types of MCU chips, and the selection of chips should consider factors such as price, mature software, and meeting functional requirements. Therefore, this design uses the 80C31 microcontroller.
Two BCD code dial switches input preset values to the MCU parallel port, and two LED display circuits send numerical values (output voltage) through the MCU serial port. The separately set "+" and "-" buttons are detected by the parallel port. The DAC receives data transmitted by the MCU data bus and determines the output voltage accordingly. Under the control of software, the MCU first reads the preset values after booting up, sends them to the display, and at the same time, sends them to the DAC to generate the same output voltage. Then continuously cycle to check if the "+" and "-" keys are pressed. If a key press is detected, it will cause the displayed value and output voltage to increase or decrease by 0.1V accordingly. If the button pressing time exceeds 0.5s, it is considered necessary to continuously increase or decrease, that is, in the "scanning" mode.
