Overview: This paper introduces a digitally controlled DC stabilized power supply with high adjustment accuracy and easy operation. The AVR series MCU Atmega8 is used as the main control unit to set the output voltage of the D/A converter chip MAX522 through different digital inputs. The DAC output voltage is amplified by voltage and current through a two-stage op amp circuit composed of μA741 and an emitter outputter ZTX453. The 5.12V reference voltage for the DAC input is generated by the LM366 integrated regulator. The host computer communicates with the lower computer through the VUSB technology unique to the AVR microcontroller, and introduces the implementation of the USB device driver under the Windows platform. This voltage source realizes the visibility and controllability of voltage value reading and setting, and can be used as an embedded power module for some test equipment. The system composition framework is shown in Figure 1. It consists of 8 serial input DACMAX522, regulated output circuit, VUSB interface circuit, signal conditioning circuit, single-chip Atmega8 and other peripheral components. It can output 0~12V voltage, step accuracy. It is 0.1V and the current can reach 2A. At the same time, the output voltage value can be set by the host computer. Figure 1 Numerical control DC regulator source composition More about Atmega8: Integrated Circuit Query Network http:// (Please read the PDF for details) Advantages of EPON: Epon Olt,4 Ports Olt,EPON OLT 4PON port,4PON Ports Epon Olt,Uplink Port,Epon 8pon OLT,Electronic Port,Optical Port,2 PON Port OLT,EPON 2 PON OLT Shenzhen GL-COM Technology CO.,LTD. , https://www.szglcom.com
The digitally controlled DC stabilized power supply is one of the commonly used devices in electronic technology. Most of the current use of the rotary switch is to adjust the voltage value, the adjustment accuracy is not high, and often jumps, it is extremely inconvenient to use. The digitally controlled DC stabilized power supply sets the digital input to the DAC through the upper computer, and outputs the adjustable step voltage. The upper computer and the lower computer communicate through a software-simulated USB. Traditional MCU and computer USB communication requires a dedicated interface chip for USB protocol conversion, such as CP2101, FT232, CH342, PDIUSBD12, SL811, etc. Chips such as CP2101 and FT232 are simple to use, but their functions are relatively simple. PDIUSBD12 and SL811 are more powerful, but they are complicated to use. And the price of these dedicated chips is relatively high, increasing the cost of the system. VUSB is easy to use, low cost, and requires only a common low-cost AVR microcontroller and few external components to form a USB system. 
More about the MAX522 data: IC query network http://
EPON adopts a point-to-multipoint structure and passive optical fiber transmission mode to provide multiple services on Ethernet. EPON technology integrates low-cost, high-bandwidth Ethernet equipment and low-cost optical fiber network technology. Compared with other access technologies, it has unique advantages, which are mainly reflected in the following aspects.
Good compatibility: EPON uses Ethernet technology, which is by far the most successful and mature LAN technology, and it can be said to be the mainstream of user LAN technology. Because EPON is only based on the existing IEEE 802.3 protocol, and realizes the transmission of Ethernet frames in the user access network through minor modifications and additions, EPON is basically compatible with Ethernet technology. Using Ethernet as the access network has low cost and good versatility, avoids complicated transmission protocols and format conversion, high efficiency, and simple management.
Low construction and maintenance costs: The EPON system significantly reduces the number of optical fibers, optical transceiver modules, and central office equipment. As the cost of optoelectronic devices continues to decrease, EPON`s per-line equipment access cost is comparable to ADSL and CM, especially the current price of optical fiber is lower than that of cable. These conditions have become the basis for the development of FTTH. At the same time, the foundation of EPON is Ethernet, and related components and equipment of Ethernet are the lowest in price. Using EPON as the access network has low cost and good versatility, eliminating the need for IP data transmission protocol and format conversion. High efficiency and simple management. In addition, there are only passive optical components such as optical fiber and optical splitter between the central office (OLT) and the user (ONU). There is no need to rent a computer room, no power supply, and no active equipment maintenance personnel. Therefore, it can effectively save operation and maintenance. cost.
High bandwidth: EPON can currently provide a downlink transmission rate of 1. 25 Gb/s, a single-wavelength uplink rate of 125 Mb/s, and can be upgraded to 1 GB/s with the development of Ethernet technology. This is much higher than the current access methods, which can meet the bandwidth requirements of various services such as broadband Internet access, video on demand, online games, video phones, and digital high-definition televisions, and fully meet the bandwidth requirements of access network customers. And it can easily and flexibly allocate bandwidth dynamically according to changes in user requirements, which can be used as the user's ultimate access method.