After the old powerstep based motor controller i improved the idea of an open source force feedback interface for direct drive wheels and other simulation interfaces with high torque demand in a modular way
OpenFFBoard consists of a simple STM32F407VG based usb interface with defined pins for SPI, buttons, leds, encoder input, CAN bus and more.
Take a look at the full development story on hackaday.io
Firmware and hardware design ressources are available on Github
A TMC4671 based motor driver which is also developed in this project as a reference can drive 2 phase steppers, 3 phase servos and DC motors at up to 60V DC and over 20A. It has an active anti backfeed diode circuit for use with power supplies and a brake resistor mosfet included. It also features highly accurate current sense amplifiers and voltage sense dividers. An onboard 5V DC converter can supply the hardware directly from the motor power supply.
I was approached to provide a floppymusic setup for an upcoming show but the issue with my own setup is that it got so many changes over the last years and was never made to be stable that it would never survive shipping.
So i decided to make a new one an fix all the problems the old setup has. Most importantly the drives are now mounted with screws instead of velco and the power supply cables are much more reliable now.
Another important change is the addition of shift registers to enable each drive when playing a note and disable it when unused. This blinks the leds and reduces power consumption a lot when used with external stepper drivers
While working on SinCos encoders i made a quick test setup from an AS5115 encoder chip and a 2204 drone motor.
Once that worked well i got the idea to use it as a steering wheel and it actually is pretty high fidelity. About 1:8 to 1:10 scale and reacts insanely fast and precise. You feel the curbs and any movement. But if the torque gets cranked up too high the motor will definetly get very hot without cooling.
Recently i found some of these rare 5 digit 7-segment modules from the 70s.
Once found in calculators and watches these tiny GaAsP LED modules amaze with their tiny, crisp, deep red segments with a whole digit not even 3mm tall.
I have created a simple breadboard friendly interface board featuring current limiting resistors and 2 shift registers (one for anodes and one for cathodes) for simple interfacing with modern microcontrollers.
OHSC will be a hybrid stepper motor controller using foc techniques based on the modern powerstep01 driver and a powerful stm32f4 microcontroller.
The goal is to develop a stepper motor controller that can operate at stall conditions smoothly the same way expensive industrial servo motors can. A high resolution rotary encoder with sub microstep resolution is used to provide feedback.
The initial idea came from researching direct drive steering wheels for racing simulators. Servo motors are often used by simracing enthusiasts as they provide accurate and strong force feedback but also come with a hefty price tag. When sacrificing some smoothness a stepper motor can be bought for a fraction of the price but i had to realize that there are no cheap modern hybrid stepper drivers available at all that would be fit for the task.
Another use case of hybrid steppers can be in robotics and automation applications where projects like odrive already allow hobby 3-phase motors to be used. Sometimes a more powerful stepper might be the better or cheaper choice
The first goal is to design a driver able to create some smooth torque and a force feedback application based on usb hid/pid. This will certainly please the simracing community and hobbyists looking to get into force feedback for cheap.
The basic principle of the current prototype is a foc loop that permanently adjusts the current electrical position by sending bursts of step impulses in stepclock mode. This allows to prevent the motor from skipping full steps and always provide the maximum amount of torque.
Based on the popular DPS5005 Module i have created a 3D printed power supply (Thingiverse STL).
These modules can also be controlled via usb with modbus. A python example is available on my github.
This allows for automatic measurements and live readouts.
A 32V old kodak power supply is fitted in the bottom of the case. For the fan a standard DC-DC buck converter was used.
The temperature stays reasonably cool when used with a fan while running at over 100W . The limiting factor here is the power supply and the 5A limit of the module. These modules should not be used without a bit of thought about airflow as the switchig mosfets can get very hot in enclosed spaces.
I wondered why i have never seen anyone making music with a siren so i had to try it myself.
It was started when i browsed thingiverse and found a nice little siren model and i had all the parts i needed around.
The interface is based on an arduino micro as a midi interface to generate a ppm signal to use with hobby escs based on incoming notes.
If the esc and motor respond quickly enough and hold the speed well it can be used as a (probably terrible) instrument.
I was pretty surprised how well it actually workded and expected it to be much worse.
The speed is not really regulated other than by the calibrated esc and a fixed voltage source and the spin up and down time depends on the inertia of the rotor and how good the esc can brake.
Fast quadcopter escs and a strong motor are preferred for this.
Some escs offer closed loop speed controlling which would be even better.
I have used a cheap racerstar lite 20A esc running blheli and a spare 2204 multistar elite 2300kv motor.