The core LC of ad analog-to-digital conversion learning board uses 8-way 8-bit AD converter ADC0809 chip. The board can measure 8-way 0 ~ 5V voltage values and display them alternately or in a single way on the four bit led nixie tube. The minimum measurement resolution is o.019v and the measurement error is 0.02v. We can make it into a multi-channel digital voltmeter.
2. Basic principles
Adc0809 is a device with sampling frequency of 8 bits and analog-to-digital conversion based on the principle of successive approximation. There is an 8-channel multiplexer in it. It can gate only one of the 8 analog input signals for a / D conversion according to the signal latched and decoded by the address code.
Adc0809 requires the input analog quantity to be unipolar, and the voltage range is 0 ~ 5V. If the signal is too small, it must be amplified; The input analog quantity shall remain unchanged in the conversion process. If the analog quantity changes too fast, a sample and hold circuit shall be added before input. The learning board adopts STC89C51 single chip microcomputer to minimize the application design. Common positive Seven Segment LED display is adopted, P1 port outputs segment code data, and P3.0 ~ p3.3 is used as column scanning output. In order to improve the driving voltage of common positive nixie tube, 9012 is used as power supply driving output.
The resources on the board include 51MCU, 4-bit LED display, 4-bit key input, 8-way 8-bit AD converter ADC0809, one adjustable analog voltage input (0 ~ 5V), ISP download interface (downloaded through RS232 serial port, which is more convenient to use), LCD1602 LCD interface, one relay output and buzzer.