No more boing!
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That's more like it! The R45 PCB Motor and the R45 PCB Motor Driver are working together to achieve the stiffness and accuracy I was after.
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R45 PCB Motor Driver mounted on the backside of the R45 PCB Motor.
Everything fits and, so far, the first tests with the R45 PCB Motor Driver look very promising!
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Square green PCB. The board integrates an onboard magnetic encoder, phase drivers, current sensing, built-in protections, and CAN communication.
Just received another package from @pcbwayofficial.bsky.social!
These PCBs are for the R45 PCB Motor Driver, a custom BLDC driver for the R45 PCB Motor.
Huge thanks to www.pcbway.com for supporting this project!
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Blender render of the R45 PCB Motor Driver PCB, a BLDC motor driver specifically designed to be used with the R45 PCB Motor.
Nothing like a blender render to better cope with the wait for the PCBs for the R45 PCB Motor Driver to arrive...
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Almost completely routed 4-layer PCB (all ground planes are shelved). Different colors show different net classes.
Nothing like a vacation day to make some progress! This is the PCB Motor Driver for the R45 PCBM.
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Render of the R45 PCB Motor with the motor driver (work in progress) on top, with the phases connectors aligned.
Started working on a driver for the R45 PCB Motor!
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Boing!
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Oscilloscope screenshot showing a clean sinusoidal waveform from a test of the R45 PCB motor stack.
After some oscilloscope and kitchen scale tests, I can confirm that the Kv of the four R45 motor stack is now 1/4 of the original and torque (Kt) is 4 times the original.
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Thermal image of 4 stacked R45 PCB Motors. A temperature increase of 55ºC from ambient can be observed.
As expected, the thermal performance of the stacked assembly of R45 PCB Motors is degraded, but not by a lot.
The image shows the results of 2.5A flowing through the Motor.
I wonder if adding thermal pads between PCBs would improve heat spreading and help avoid hotspots.
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Started tests stacking various R45 PCB Motor boards.
These are 4 boards stacked in a series configuration. Will I get close to 4x the torque for the same current? How will the stacked assembly perform thermally?
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Field Oriented Control is working on the R45 PCB Motor!
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Oscilloscope capture showing the sinusoidal line-to-line back-emf of the R45 PCB Motor while spinning.
Beautiful sinusoidal back-emf coming from the R45 PCB Motor!
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Thermal test results when 3 A are flowing through a single PCB of the R45 PCB Motor. The maximum reached temperatures are near 90 ºC.
A single PCB of the R45 PCB Motor can safely handle a continuous current of up to 3 A.
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First spins of the R45 PCB Motor!
Right now it's running in open loop mode (without an encoder).
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All the magnets have been glued.
Inspecting the fields with a magnetic viewing film reveals that the Halbach configuration behaves as predicted by the simulations.
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3D-printed rotor with rectangular neodymium magnets partially inserted into radial slots. The magnets alternate in orientation, forming a Halbach array. Some magnets are slightly lifted due to magnetic repulsion, highlighting the difficulty of assembly.
Placing the magnets in a Hallbach configuration is trickier than I initially expected, the magnets do not want to stay in place. Time for CA glue!
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3D-printed rotor for the R45 PCB Motor, with 40 slots arranged radially for magnet placement. Below the rotor, 40 rectangular neodymium magnets are lined up, each marked with a white dot to indicate polarity.
Today I received the magnets for the R45 PCB Motor.
The magnets have been marked and now it's time to place them one by one in a Hallbach configuration.
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Spreadsheet showing various stackup options from JLCPCB and PCBWay, prices and copper percentages.
In order to achieve high torques in a PCB Motor the amount of copper plays a major role.
The following spreadsheet has been used in order to evaluate what some of the best available options are.
PCBWay's 10L 6oz stackup looks very promising but it's expensive for low quantities...
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FEMM simulation showing the magnetic field lines and flux density of the Halbach magnet array used in the R45 PCB Motor.
The R45 PCB Motor uses a Halbach magnet configuration, which gives it two key advantages:
1. It concentrates the magnetic fields to one side, like having a back iron.
2. It produces a more uniform field even with rectangular magnets instead of arcs (cheaper).
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Round green PCBs stacked. The phases of the motors can be appreciated.
New package from @pcbwayofficial.bsky.social !
These PCBs are for the R45 PCBM, an evolution of the Comb PCB motor with higher torque capabilities.
The PCBs are 0.6mm & 4 layers. One of the things I want to test is to stack them.
Thank you www.pcbway.com for sponsoring this project!
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Thermal image of the Comb PCB Motor during testing with 1.6 A of current. The copper windings on the PCB appear hot, with the highest recorded temperature shown as 98.4 °C.
Performed some thermal testing on the Comb PCB Motor.
As a result, its rated current has been found to be 1.6 A.
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Side view of the Comb PCB Motor, the new bearing holder is much taller than before.
With the addition of a second bearing the Comb PCB motor is certainly not as sleek, but the mechanical play has been reduced by a lot.
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CAD view of the next revision of the Comb PCB Motor.
Started designing the next iteration of the Comb PCB Motor. This time I'm going for torque instead of cuteness. Bigger, more copper, more poles, more power.
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Trying out position control on the Comb PCB Motor!
A more agressive loop could be achieved with more pole pairs or the addition of an encoder.
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Closed-loop speed control on the Comb PCB Motor!
Using feedback from the hall sensors, the motor tracks the target speed. Not perfectly tuned yet, but already doing a pretty good job.
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Oscilloscope screenshot showing the differential voltage between two phases of the Comb PCB Motor during free spin. The waveform is a trapezoidal back-EMF signal with a peak-to-peak amplitude of ~900 mV and a period of ~10.3 ms, used to estimate the motor’s Kv.
More characterization tests for the Comb PCB Motor! This time I measured the Kv by spinning the motor and measuring the back-emf.
These are the results:
- KV_measured = 6450 RPM/V
- Kt_estimated = 1.48 mNm/A
- Kt_simulation = 1.55 mNm/A
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Oscilloscope screenshot showing a decaying sinusoidal waveform used to measure the inductance of the Comb PCB Motor. The waveform indicates a resonant frequency of 250.89 kHz, from which the phase inductance is calculated to be approximately 2 µH.
Continuing with the Comb PCB Motor characterization, I ran some tests to estimate the phase inductance.
The result: 2 µH per phase.
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After the rework the Comb PCB motor is spinning beautifully! Next step closing some loops.
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Close-up of the Comb PCB Motor showing a rework.
That’ll do it! The Comb PCB Motor has been successfully reworked to swap the two misplaced hall sensors.
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