為了解決磁放大器性能測試過程中，需要對其供給不同數值恒定電流的問題，設計了一種基于DAC7512和單片機的數控恒流源系統。該系統采用AT89C51作為主控器件，將計算機發送的電流控制字命令轉換為D/A轉換器控制字，通過模擬SPI通信接口，寫D/A控制字到DAC7512，從而控制其輸出相應數字電壓值，經差動縮放電路、電壓/電路變換電路和功率驅動電路，最后輸出恒定電流。實驗結果表明，恒流源輸出電流調節范圍為-45~+45 Ma、精度為±0.1 Ma，分辨率達0.024 4 Ma，具有應用靈活，外圍電路簡單，可靠性高的特點。該數控直流恒流源也可為相關產品的測試系統研發提供參考。
Abstract:
In order to solve the need to supply different values constant current for the Magnetic amplifier in testing process， numerical control constant current source system was designed based on DAC7512 chip and microcontroller technology. The system used the AT89C51 as the Main chip， which can convert the current control word from computer into to D/A control words. And the system wrote D/A control word into the DAC7512 chip to control the output voltage value by the SPI communication interface， which can output corresponding constant current figures by scaling circuit， the V/I converter and power drive circuit. Experimental results show that the current source output current adjustment range is -45~+45Ma， accuracy is ± 0.1Ma， and resolution ratio is 0.024 4Ma
The PCA9670 provides general purpose remote I/O expansion for most microcontrollerfamilies via the two-line bidirectional bus (I2C-bus) and is a part of the Fast-mode Plusfamily.The PCA9670 is a drop-in upgrade for the PCF8574 providing higher Fast-mode Plus(Fm+) I2C-bus speeds (1 MHz versus 400 kHz) so that the output can support PWMdimming of LEDs, higher I2C-bus drive (30 Ma versus 3 Ma) so that Many more devicescan be on the bus without the need for bus buffers, higher total package sink capacity(200 Ma versus 100 Ma) that supports having all 25 Ma LEDs on at the same time andmore device addresses (64 versus 8) are available to allow Many more devices on the buswithout address conflicts.
The PCA9671 provides general purpose remote I/O expansion for most microcontrollerfamilies via the two-line bidirectional bus (I2C-bus) and is a part of the Fast-mode Plus(Fm+) family.The PCA9671 is a drop in upgrade for the PCF8575 providing higher I2C-bus speeds(1 MHz versus 400 kHz) so that the output can support PWM dimming of LEDs, higherI2C-bus drive (30 Ma versus 3 Ma) so that Many more devices can be on the bus withoutthe need for bus buffers, higher total package sink capacity (400 Ma versus 100 Ma) thatsupports having all 25 Ma LEDs on at the same time and more device addresses (64versus 8) to allow Many more devices on the bus without address conflicts.
The PCA9672 provides general purpose remote I/O expansion for most microcontrollerfamilies via the two-line bidirectional bus (I2C-bus) and is a part of the Fast-mode Plusfamily.The PCA9672 is a drop-in upgrade for the PCF8574 providing higher Fast-mode Plus(Fm+) I2C-bus speeds (1 MHz versus 400 kHz) so that the output can support PWMdimming of LEDs, higher I2C-bus drive (30 Ma versus 3 Ma) so that Many more devicescan be on the bus without the need for bus buffers, higher total package sink capacity(200 Ma versus 100 Ma) that supports having all LEDs on at the same time and moredevice addresses (16 versus 8) are available to allow Many more devices on the buswithout address conflicts.
