Brushless Motor and Driver Business Card Kit

Description

Designed for learning, this electronic business card PCB will guide your build of a brushless motor and provides the opportunity to experiment with control algorithms. Try delta and wye winding configurations and experiment with rotor and magnet designs as much as you want. The circuit is illustrated with test points on the front side, and the components are all placed on the back side.

Everything is open source and freely accessible via links shared below. Design tools used are KiCAD (electronics), Inkscape (graphics), and OnShape (mechanicals and motor).

Details

I've had this idea in mind for a while and the Hackaday Business Card Contest is the perfect motivation to bring this idea to life. I'm in a frantic scramble to finish the design and get a board running before the close of the contest!

Features

Built-in schematic with illustrated test points
Built-in motor with option to connect external motor and hall sensors
Adjustable winding configurations via solder jumpers
Simplified voltage feedback from the motor phases for position (using 328PB analog comparators with interrupt feature)
Optional connections to external motor and hall sensors
ATmega328PB - Arduino bootloader (via USB-FTDI cable)
Capacitive touch buttons (Mode, -, +, Select) to control mode, speed, and who-knows-what?
RGB User LED
QWIIC/Stemma I2C port
R/C connector input with tach output
ISP port
Power switch to select USB or battery power source
SAO port for an SAO OLED, of course!
Simple Arduino code for you to learn and expand upon

I've been inspired and learned a lot from these folks which I'm applying in this project:

Check out this playlist to learn more about brushless motors and controllers: https://www.youtube.com/playlist?list=PLgr0YZUR4CSVKWWj0__yitdxPeQSaBse1

This project has come to life in a hurry and is not optimized. These are some forward looking features I'd like to incorporate in a future revision:

Voltage regulator (5V) to allow 4x "AAA" or 1S LiPo power options
USB C port and built-in USB to Serial conversion, maybe a different MCU solution all-in-one
More LEDs to visually indicate which transistors are active, and coil polarity
Built-in single row header to easily connect to scope/logic analyzer such as Analog Discovery
A hall sensor (or a three) built-in to the PCB for feedback capability
More complete analog feedback capability
The rotor is easy to swap out with other pole counts, but other than the wye/delta configurations jumpers for the windings, they are not easy to change. Perhaps the windings could be a separate and removable PCB to enable experimenting with different windings all together?

I'd like to know your feedback and questions in the comments below!

Files

BLDC_BIZ_CARD_V0.1_Schematic.pdf

Schematic plotted from KiCAD, ISP port rotated to match PCBA position

Adobe Portable Document Format - 429.67 kB - 06/29/2024 at 18:31

Preview

BLDC_BIZ_CARD_V0.1_Gerbers.zip

Gerber package

Zip Archive - 215.29 kB - 06/27/2024 at 13:25

Download

Project Logs

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I2C and SAO OLED are alive!
Andy Geppert • 2 hours ago • 0 comments

Nice to make some relatively easy progress and confirm more of the board is working:

Time to get serious about installing the 3 half bridges and bringing up the PWMs and some open loop motor control!
NOTES:
1) The cable is a USB to 5V FTDI converter, for programming. No built-in USB capability on this first prototype. I'd like to add USB-C later on.
2) The yellow and black pair of wires is to power the logic side, when the FTDI cable is not used.
3) The red and black pair of wires is to power the motor driver side, and allows me to current limit that part of the circuit during bring-up.
4) There is an open solder jumper I can use to bridge logic and motor power so only one power source is needed.
On burning a bootloader to an ATmega328PB...
Andy Geppert • 3 hours ago • 0 comments

I'm trying to bring up the MCU on the board, but I cannot get an accurate or consistent MCU ID out of the chips. So, I'm set aside that struggle for later. Just swapped in a 328PB from an Arduino Uno, and it's alive and well at 16 MHz! RGB LED responds correctly, and the serial port is spewing data.
I've been able to burn a boot loader to a Poll A-Star 328PB with the AVR ISP mkII, but I'm missing something with the fresh 328PB's I bought from Digi-Key. Since a swapped in 328PB works fine, I think the basic circuit and connections are in good shape. I'm not going to try and re-burn the boot loader in the 328PB I swapped in now... maybe later.
On to bringing up the I2C and SAO port with OLED next.
The boards are here!
Andy Geppert • 2 days ago • 0 comments

Boards showed up today! Wrapping coils! Testing!
I abandoned the plastic mockup and have the coils wound. Continuity and wiring pattern seems good. None of the components are installed on the back of the board yet, so I'm using the three pin "alternate motor" header as in input to do testing.
The rotor moves a little bit with manual voltage pulses, but the small brushless motor driver I tested with can't get the rotor to turn. There is a lot of room for testing and optimization. Gaps, flux density, coil and magnet coils... guaranteed learning of one kind or another awaits me.
I'll resume tomorrow evening...
Roughing out the concept in CAD
Andy Geppert • 3 days ago • 0 comments

This is the board design concept, with the rotor shown in orange:

The CAD design is available in OnShape: https://cad.onshape.com/documents/f519e018cd04a070474f7458/w/7211a2b8f86f81003258f57c/e/c9c6c988519f346738a797cf?renderMode=0&uiState=667d5e72c0a2c30711b7db9f

The [3D printed] rotor will have 8 magnets that snap into it. The magnets are cylindrical, 1/8 x 1/8 inch length and diameter. Two small bearings press in to the top and bottom of the rotor. A fixed shaft is pressed into the rotor support base (light gray) underneath. It all comes together like this:

I don't have boards yet, but I can still make progress with all of the mechanical elements and the windings. On the right side in the "S" shape is the winding tool, also 3D printed. It serves to smooth out the wire, and provides drag on the wire to make it easier to wind. Surprisingly, it worked on the first try, and it's quite easy and fast to wind the coils. WAY FASTER than weaving core memory! So progress is very good on the mechanicals now. The rotor "spins like a low-end fidget spinner" and is just as fun. Even if this whole project doesn't work, I'm gonna have a great business card sized fidget spinner...

Some initial testing on the coil windings to evaluate current and torque:

The motor kicks! Less than 1 Ohm in the winding, .3V and .3A, and the rotor kicks into position to align with a coil. It's a beautiful thing. Look for more progress tomorrow night. I think I'll be able to get it spinning with an off-the-shelf brushless motor driver.
Brushless Motor Business Card Concept
Andy Geppert • 5 days ago • 0 comments

This is the first sketch I drew to capture the concept on paper:
My vision is to show the entire motor concept from the front side of the card, including the most relevant schematic elements. By having everything accessible from the front side, I can experiment and probe the different signals, along with making firmware changes, in one clean set-up.
Next I started to think about the structure and placement of headers:
Making the motor have an optional WYE or DELTA winding configuration through solder jumpers will allow even more experimentation. The winding configuration has the potential to change the performance characteristics significantly, so I wanted that option to be available.
Additionally, I have found that having four buttons enables easy access to more functionality in the future, so that needs to be part of the design. Furthermore, an SAO port lends itself to expandability and makes it easy to install an SAO OLED, which I've been making and using recently.
Of course, more fun ideas start to flow. I'd like to have LEDs which indicate which coils are energized, and the polarity. Or maybe add LEDs to the rotor itself to visualize the pulses of current in the coils through inductive coupling?! These ideas will have to wait until I get the basic functionality enabled.