HOLY ESC

HOLY ESC

My effort to bring an open source, closed loop ESC to life.

From hardware to firmware.

This image was edited using AI to remove stickers that were bloating the image.

You can order the FULL BUILD in a couple of click right : (Todo : add link once project post is approved)

[!NOTE]
This ESC was featured in one of my youtube videos. You may be searching for the AtMega based firmware and perfboard BOM / Schematics. I did not put these here as the design worked but is not reliable. You can open an issue if you really want it and I'll add it to some "deprecated" folder in the repo.

THE PROJECT

The HOLY ESC is a BACK EMF based ESC, theorically able to be loaded up to 25Amps and more. But it serve educational purupses and has not be stress tested for any applications yet.

It was designed on KiCad 9 and aims at using cheap components to make the design accessible to all.

This design target drones and is planned to be tested on such applications soon.

Here are views of the PCB layers:

Usage

Hardware

The hardware folder contains the KiCad9 files that you can open and modify as you like for your own needs, as long as you respect the project licence at the root of this repo.

Software

The sofware part is a bit more tricky.

If you get the board manufactured, you will need to load a firmware on it. In this repo, I distribute AM32 binaries made specifically for this ESC.

Here is the procedure to start spinning a motor:

1. Connect the HOLY ESC to your host PC

First you'll need to connect the ESC's STM32 to a host computer.

So you'll need :

• A 15V or so power supply to power the board.
• A Stlink V2 (or any clone should work as long as it has SWD)
• Download STM32CUBE programmer software

So connect the ESC to your power supply on the dedicated pads (Labeled "+" and "-" on the back of the PCB), I suggest limiting max current to 1 Amp in case a fault arises. Red LEDS should turn on, indicating a good supply of voltage into the board.

Connect the ESC SWD headers to you STLINK

And plug it into you computer.

Launch STMCUBE Programmer, click connect and it should recognze the MCU on the ESC board.

At this point you can also connect a BLDC motor on the 3 phases pads using solder (labeled A; B & C on the back of the board).

2. Load the Firmware (EASY WAY)

Once everythoing is wired up correctly...

Use STM CUBE Programmer software (or st-flash fo cli) to prgogram the <repo>/software/holy_esc_firmware_am32.bin binary on the MCU (which is a STM32F051K8U6) @ base address 0x08000000.

This binary contains the AM32 build, along side the bootloading code and the eeprom.

2. Load the Firmware (DIY WAY)

If you decide to build the firmware from source to fit your need, asking a LLM to guide you through the AM32 targets.h modifs and from-source-building makes this process pretty easy.

Once you've got your build, you gotta flash it onto the MCU, alongside a bootloader and a eeprom data region.

The procedure to load these things is described there:

https://github-wiki-see.page/m/AlkaMotors/AM32-MultiRotor-ESC-firmware/wiki/Memory-Layout-for-flashing-with-a-St-link?utm_source=chatgpt.com

You can use STMCube's "Erasing and Programming" tab to select a binary and load it to a specified address. Just load each binary at the right address and you should be good to go.

To verify if you corecty modified a memory region, you can use the "Memory and File editing tab" to read a specific memory region, to check if it changed from the default values.

Bootloading and eeprom binaries are found in the page linked above. You will find the specific binary built for this specific board in ./software/

[!TIP]
If you are hardstuck on trying to lad a firmware, you can open an issue to get support.

Once the firmware is succesfully loaded, connect a BLDC motor to the phases pads (labeled A, B and C at the back of the PCB) using solder. Turn on your power supply (with STLINKV2 connected to PC or completely off the board to avoid asserting reset) and you should ear 3 beeps, indicating the motor is ready to armed !

Congratulations ! Now to spin a motor, you can use an arduino + voltage divider as a quick test, like I did in the video (use an LLM to write the arming sequence and speed command PWM generation) or use a servo tester / real flight controller.

[!INFO] Telemetry feedback and AM32 monitoring tools not tested yet

Future Work

• Replace the STM32F051 with a cheaper and more available package / version. (right now its 5+$ !!!! When I made the design it was like for 3-4$ MAX before going out of stock on LCSC)
• Add vias under the FETs as well. I did not initially did so to avoid assembly problems but adding a few vias on the mosfet pad should drastically increase Amperage tolerance.

Inspirations & Thanks

A big thank you to these actors, who were a great source of inspiration in my learning and designing process !

• The Engineering Techie
• Electronoobs
• 10x Aero
• AM32 Community and posts

Self Promotion

• The youtube channel which I featured this project on : BRH YOUTUBE
• My Blog : Blog Link