Electronic Load

Devlog #04

Overview

Control board is now done as well!
There is a lot going on so I’ll break it down a little.

MCU

There is an STM32G431. It functions as the brain of the device. It handles everything: current regulations, communication with the user using the display and USB.

VRM

Board is powered from 24V DC and it is regulated to 15V and 5V with linear regulators. It powers the frontend and op-amps on power boards. There are 2 more rails: 12V for fans and 3V3 for entire digital section. Both are switch mode regulators, since both need to be high current and noise is not a big concern

Now I will wrap up the project and make it ready for funding. It looks great and I’m really proud of it.

Devlog #03

Overview

The first PCB is done! It is the power module in a 100x80mm format.

Traces

Each module is designed to handle 15A. There will be 4 of them for 50A so in reality it will be only 12.5A on each module. Still, traces need to be quite wide. I decided to remove solder mask on the traces that were too wide to route properly and needed to be made thinner.

Current measurement

2 INA180 current amplifiers are used to measure current. Why 2? Because I want to measure 2 ranges: 15A and 1.5A. And that’s also the reason why there are 2 shunt resistors on the screenshot below.

Next Steps

Now I will focus on the control board. There is a lot going on there so it may take a while

Devlog #01

Overview

So MCU board schematic is done. Nothing too crazy, but there are a few interesting things.

Fan connectors

I put 4 connectors for fans. Why? Well, I may not need that many but they might come in useful. I need 1 connector for a pump and 1 for aio fans. Maybe I’ll use 3rd one for chassis fan and 1 will be as a spare.

There isn’t a lot more to say about it. After all its just a PCB with an MCU just like any other. The difference between this one and any other lets say nucleo board is just in special connectors, eeprom and temperature sensor.

Devlog #01

I started working on the project and well… it’s a lot. The electronic part seems simple, but there is so much more.

Requirements

Before diving deeper intro the project I would like to set some basic requirements:
Max Voltage: 60V
Max Current: 50A
Max Power: 2kW

Architecture

I decided to split it into a few boards. To handle power up to 2kW I need to be very careful about it. There will be 12 IRFP250N power Mosfets split into 4 separate boards. All will be connected to control board and power management board. You can see schematic of the mosfet board below.

Cooling

And now the most important part. Mosfets can dissipate up to 2kW. That’s a lot. And I mean a LOT. My electric space heater has the same power rating. If cooling isn’t done properly the device will fry. That’s why I decided to use water cooling. The idea is to slap one of those big AIOs like in PCs to a copper block and mount 12 transistors onto the block. This way the heat will be quickly transferred away from the mosfets and with help of a few powerful server fans it should be good enough. (Well not for my ears, but I’ll accept it I guess)

Anyway, everything starts coming together. I will soon start designing control circuitry. It all looks quite nice and I am excited to continue this project!