Blog on Felipe Lira

PCB Design Part 1

Mon, 06 Jan 2025 21:43:00 +0000

Disclaimer

This project includes images of assemblies that use third-party components from Phoenix Contact. The electronic housing shown in the images is a product of Phoenix Contact and is used here for reference and demonstration purposes only. All product names, logos, and brands are property of their respective owners.

PCB Design

We’ve arrived at the part I like the most: turning this:

Into this:

Below, I explain the step-by-step process I used and how I organized my ideas.

Schematic Design Part 2

Sat, 28 Dec 2024 20:27:00 +0000

Now I’ve finalized the latest modifications to the schematic. The Modbus circuit was challenging to design in the most cost-effective way, but I believe I’ve found a good combo that still maintains the capabilities of an isolated RS485 interface IC.

Modbus RTU

I’m using a robust IC, the THVD1520, with additional protection, and the ISO6742 as a digital isolator. This setup is cheaper than using an isolated RS485 IC directly since the ISO6742 becomes more affordable when purchased in quantities of 10 or more.

Schematic Design Part 1

Sat, 14 Dec 2024 18:48:00 +0000

Microcontroller Selection

I’ll start the schematic by choosing the microcontroller.

Its selection is essential to determine power supply, analog circuit, and communication.

It must be supported by the Autonomy software, so let’s check which models are supported and study their availability and prices:

Arduino Opta - Uses the STM32H747 microcontroller at $20. No chance.
esp32 - More affordable, but I’m paying for Wi-Fi, which I don’t need right now.
esp8266 (node-mcu board) - A $4 board with everything I need and USB programming. However, it’s limited in terms of possible inputs and outputs.
Mega / Due - Has far more features than I need.
MKR Series - Wi-Fi and lots of features.
Nano Every - €15 for a single board.
RP2040 - A strong candidate, its board costs around $6 but has limited IO.
STM32F103CB (Blue Pill) - The best candidate so far. It has plenty of IOs, and I can buy it for $3 in Brazil.
STM32F411CE (Black Pill) - More expensive than the Blue Pill.
Uno, Leonardo, Nano, Micro, Zero - Atmel microcontrollers are usually more expensive with fewer features.

Therefore, I will use the Blue Pill’s microcontroller for the development of the Lira-CLP.

Project: Lira-PLC

Wed, 11 Dec 2024 22:25:00 +0000

Updated: 14 Dec, 2024

I was browsing Mercado Livre the other day looking for a USB-RS485 converter when I came across a mini PLC for panels. At that moment, I thought: this would be a great project to publish on this site.

And so, it is with pleasure that I begin my first public project: the Lira-PLC.

The idea is to make it a completely open-source project while showcasing the entire journey of developing a product like this, from conception to testing and improvements.