My open source PCB motor is an attempt to build a smaller, cheaper and easier to assemble micro brushless motor.
What unique about this motor design is that the stator is printed on a 4-layer PCB board. The six stator poles are spiral traces wounded in a star configuration. Although these coils produce less torque compared to an iron core stator, the motor is still suitable for high-speed applications.
The current prototype has a 3d printed rotor with a 16mm diameter.
My PCB-Motor is made from a 6-pole stator printed on a 4-layer PCB and a 4-pole 3d printed rotor. Its has an outer diameter of 16mm and is rated at 1 watt.
I had this idea when I was trying to design a small compact drone. The PCB motor is much cheaper than other micro brushless motors and also easier to assemble. My goal is to make the rotor part of the BOM and mounted just like any other component on a PCB.
I have finally finish my PCB Motor with the integrated ESC! Made this quick video showcasing it:
The PCB was hand soldered. It took me a little while to get it to work because I had some soldering flux residue on one of the motor driver chip that was acting as impedance. This was triggering the driver's on-board protection circuit. But after removing the chip and clean its pads, it was up and running.
I have managed to fit the ESC in such a small area by soldering parts on both sides of the PCB and using the smallest footprints I could find! Both the MCU and motor driver have a 3x3mm qfn package and most of the other discrete components are 0201s!
I'm currently making another video explaining how i design this driver and what were the challenges involved! So I will be releasing its schematics and gerber files in the next few days :)
I love designing electronics that fit in very tiny space. My 4-layer brushless PCB Motor is currently 16mm in diameter. So how can I make it smaller?
This 16mm design is already pushing the limits by having 4mils (0.1mm) track width and clearance. Using thinner pcb traces is possible, but would make its price (for prototyping) explode. My intent is to make this open source motor accessible to others, so it doesn't makes much sens to go in this direction. So I'm sticking to 4/4mil traces.
My motor has around 40 turns, so going much lower than that would make the coils too inefficient and the pcb would heat up way to much. Based on a my pcb coils tests the minimum number of turns for 4mil should be 40 turns and for 5mil it should be 60 turns, not to exceed 70°C with a constant (100% duty cycle) supply.
The only remaining option to try and make it smaller, is to increase the number of layers to decrease the number of turns per layer. The current design has 10 turns per layer, so for this tiny 6-layer motor I decided to go for 6 turns per layer, having a total of 36 turns. Setting a tight clearance of 4mil, the total diameter of the motor end up being 11mm.
The extra two layer, increased the number of vias in the middle of each coil to three. This naturally formed the spiral to have a triangular shape which use the area of the magnetic field more efficiently.
Another natural advantage of using a 6-layer pcb, is that the thickness between each layer is much smaller which increases the magnetic field strength.
For this design I had to make some changes on the rotor, because I couldn't find a bearing small enough to fit at the center of the pcb (smallest bearing available is 2mm). So what i decided to do is extended a stationary-shaft from the pcb, and connect the bearing on the rotor. I'm still designing the 3d-printed part, so I will post more info on that soon.
I have just ordered this 6-layer pcb motor from JLCPCB which were kind enough to sponsor this design.
This is the drone concept that gave me the idea of trying to create the PCB motor and spherical folding propeller! Both of these projects need a lot more work and improvement to make this drone feasible but at least now I have a starting point :)
I finally ordered a new PCB motor with an integrated ESC. I have managed to package the circuit in a very small space, 30x16mm including the stator. For now I have ordered the same star winding configuration that i've used in the first prototype. I'll be ordering more configurations soon.
The circuit basically consists from:
Hall Sensor (US1881) to detect the magnets inside the rotor.
MCU (PIC16F1503) - I have shifted from the DSPIC33EP128 to the PIC16F1503. This MCU has less computational power (not much is required since I am no longer considering sensorless control) but is packaged in 3x3mm chip and is around $2 cheaper
3-Phase Motor Driver (STSPIN230) - which is rated at 1.3Arms, and has several types of fault protection build-in.
A filtering circuit to supply the micro.
I will upload all the source code and gerber files once the PCB arrives and verify its functionality. Keep tuned!