The heart of the system is an Atmel ATmega328P AVR microcontroller with 32kB of Flash and 2k of RAM running at a whopping 16MHz. It interfaces an I2C 12bit DAC (the MCP47FEB21A1) and the LTC2992 dual power monitor chip.
The USB serial interface uses the MCP2221A bridge. The display is a classic 16×2 LCD.
On the analog part, 10mΩ and 0.2Ω shunt resistors are used, coupled with two W9NK90Z N-ch power MOSFETS. The heatsink was salvaged from an old graphics card. Attached are a 10k NTC and a generic fan (12v @ 200mA, 80mm). Current regulation is achieved through the help of a MCP6H02 opamp, and a carefully designed feedback network which guarantees the specified rise time with little to no overshoot.
The layout was done using the Eagle software (v9.5.2). Gerbers, Eagle project files, top and bottom views are available on the
pcb folder. PCBs were printed using JLCPCB service. The schematic is available in a pdf and Eagle
.sch format as well.
Several user-definable bi-color status LEDs are included, such as Load ON/OFF, TX & RX, acquisition blink, as well as a power LED.