[kreutz]

Hello:

Yesterday I received one BLDC motor and controller set. I ordered it a few days ago ($90.00 + tax) just to find out how to modify it for my own purposes.
(Tried to post the photos but they are to large and I will have to reduce their size)
The idea is to use, if possible, some or most of, the original components in order to make it do what I want, without having to completely redesign the controller board and user interface. But, it all depends on having access to each individual component's data sheet and finding out how the circuit works, before deciding what to change.

Specs known so far:
550W on the motor label.
110Vac line input
500 - 4500 rpms controlled by a hall sensor-magnet contraption. (yes, it is one of the myriad "servo controllers" for a sewing machine floating around the internet) Not a real servo, of course.
Real BLDC motor specs are completely unknown. We will have to measure them, but first, I have to reverse engineer the main board and the user interface board. Apparently not a difficult task.

What I want it to do:

Isolate my control signals from the controller which is not isolated from the power line.
Controllable by step-direction, or -10V/10V signal in CNC mode
Manual Switch for forward-off-reverse, and a Potentiometer for speed control in Manual mode
Emergency stop (both remote and manual button)
Motor tuned by isolated usb connection to PC, if possible, using auto-tuning for the PI gains of the speed and torque control.

I know that some of you will tell me to use the magnetic contraption as seen on you-tube videos, and forget about all of the above, but that is where the fun is!

Stay tuned....


kreutz

[kreutz]

Photos:

[kreutz]

SPEED CONTROL USING POTENTIOMETER

all resistors 1/4 W

Potentiometer 4.7 k or 5 kOhms 1/2 W or bigger (due to shaft Isolation issues), I used RV24YN20S 5K Potentiometer, you might have to alter the values of R1 and/or R2 depending on tolerances.
Enjoy!!

kreutz

[kreutz]

The controller board has:

line voltage input connectors, fuse, bridge rectifier, 2x 680 uF/250Volts capacitor bank, 1 dc/dc converter ic (Viper22a-E) and associated circuit for +15Volts power supply, and a 5 volts regulator ic.
3 channels IGBT driver IC (ID7T6036), 6 x 20A/600V IGBTs (Xiner XNF20N60T)

1x 0.015 ohms 3 Watt sense resistor for motor current overload measurement, 1 x 510 ohms 1 Watt resistor (seems to be part of a soft start circuit to charge the capacitors bypassed by one of the relays when the 15 volts is present).

1 x 32 pin microcontroller IC (MM32SPIN05PT 32-bit Micro controller based on ARM Cortex M0 , 32K flash, 4k Ram) the only thing I know so far is that it is supported by Keil.

The heatsink is pathetically thin.

[kreutz]

For a faster 0 - Vmax (approx 2 seconds) response replace R2 by 4.7 Kohms and R4 by 180 Kohms resistor (when using 5 Kohms potentiometer). The original circuit in the Rev 001 schematic has a response time of about 3 seconds from 0 to Vmax. I don't recommend too fast settling time because of the lack of a "non-destructive" maximum current limit on the original controller. I don't like to put my luck to test doing sudden accelerations and decelerations, as it was programmed from the factory, don't compare a lathe spindle to a sewing machine's inertia.

I am also working on a PWM (isolated) speed control and On/OFF, I will be testing it in the next few days.

Note: If you are using a 4.7Kohms potentiometer keep R2 value at 4.3Kohms.

[kreutz]

Photo with labeled components. Bottom left are the two relays.

[kreutz]

This is definitively not the time to do new projects, still most of the parts, that come to mind when planning a new design, are out of stock. Even the development boards. I will continue to work with the ones I have and after getting a solid prototype, working as I want, I will sit and wait for the semiconductor industry to get back to what it was a few years ago.

I was evaluating the ST motor control SDKs, I had to go back to the previous generation (SDK5.4) since the latest MC-SDK6 is a joke. No examples whatsoever, almost no choices of microcontrollers for the motor control workshop, the information on the internet is for older SDKs not compatible to the CubeIDE, no new video tutorials for the newer MC SDK6 nor information on "how to". The same applies to MATLAB, the new 2022 simulink embedded support package for STm32 controllers is not compatible with the new StcubeMx version, the same for Ti C2000's. We are frozen in time to the times before covid in the software side, but not even near comparison on the hardware side.

Rant off!

[Al_The_Man]

Seems to be a little bit of a masochistic task
If you intend to modify the board, I would have thought that a program listing of the 32-bit Micro would be needed.
It may have been easier to design from scratch, Incidentally, what pole count does the motor have?

[kreutz]

6 magnets, 3 pole pairs.
I don't think the program listing will be available, Looking at the microcontroller's datasheet, there is little chance they are doing anything else than 6 steps commutation, using the 3 hall effect position sensors mounted on the stator, trapezoidal PWM speed control or in the best case sinusoidal commutation, . So, starting writing code from scratch would be better than to wait and pray for the source code.

Resistance measured between two phases (Y connection) = 5.1 ohms (including cable and connector resistance), Inductance @ 1khz between two phases = 35-36 mH, inductance changes with rotor position.

Regards,
kreutz

[kreutz]

WHAT IS FIELD ORIENTED CONTROL (and how to control Permanent Magnet Synchronous Motors (AC permanent magnet servos and BLDC) ?

Here is an explanation:

https://training.ti.com/field-orient...-magnet-motors

[kreutz]

Found another guy trying to reverse engineer a similar BLDC controller, possibly an older model of the one I have. Look at: https://www.candrian.gr/index.php/re...or-controller/

I am currently trying to reverse engineer the PCB and produce an schematics, also connecting test points for testing the gate driving signal waveforms. For anyone trying to do the same, please, remember to use an isolation transformer (1000VA minimum) to feed the controller, there is a potentially lethal line voltage present at the pcb ground otherwise!! Protect yourselves and your test equipment!

[kreutz]

The relay to the right on the pcb (top side) is used for the voltage doubler function for 120Vac operation, the voltage doubler raises the filtered rectified voltage to approx 310-320 Vdc, the two big capacitors are in series connection across the 320Vdc bus. In case of 220Vac line input the relay on the right is not populated, and, of course, there is no need for voltage doubling.

Here is a photo of the bottom side of the pcb:

[kreutz]

The documentation on the micro controller's manufacturer page is mostly in chinese, no english translated useful documents on their page, apparently they have their own ISP programmer, MMlink emulator and programmer, but I wan't able to get more info, not even a user's manual. So, the option of replacing the firmware on the original pcb's micro-controller is closed, so far.
I have a few ST Semiconductor's evaluation boards at hand, as well as their high voltage motor evaluation board, maybe that is the way to go and let's forget about modifying the original board for the moment. I checked on the internet and the ST micro controllers, on the evaluation board I have (STM32G474RE), are "out of stock" . So it will take time to make prototyping boards and populate them unless I desolder the micro controller from the evaluation board to test my prototype pcb. I am retired, so there is no hurry at all.

I'll keep you posted, on the status of the project, from time to time.

Regards,

kreutz

[kreutz]

Here is the photo of the controller's front panel. I just realized that there are many of this sets for sewing machines around but there are differences between them.

[kreutz]

Here are the ST evaluation boards I was talking about, I will be starting to write software for this project in a little while, just waiting for parts to repair my 400Vdc/5A lab power supply to start testing step by step. Most probably the first try will be Field Oriented Control of the BLDC motor, will try "sensored", using the 3 Hall sensors present in the motor, or "sensorless" and probably use the sensors for rpm display only. There is time to also try the 6 steps commutation, similar to the actual implementation, just to compare them. I also need to test my low voltage lab power supplies, more than 10 years without use won't make them any better, don't want to risk damaging the eval. boards.

[kreutz]

I was prepared to give a large speech about why "NOT ALL THE PERMANENT MAGNET BRUSHLESS MOTORS AND CONTROLLERS ARE CREATED EQUAL" and describe the different method of "Conmutation Control" available for BLDC motors and their advantages and disadvantages. Terms I already used on the prior posts, such as "6 Steps Conmutation", "Trapezoidal Commutation", "Sinusoidal Conmutation" and "Field Oriented Control" (FOC) need an explanation so you all can follow this thread without overloading your brain with unknown expressions. I will, in the following posts, keep out all the mathematical part and try, as much as possible, to make it easy to understand what is involved in the development of a controller for BLDC motors, in Positioning, Velocity and Torque applications, as required by CNC machines.

Many will think that having a BLDC motor and the cheapest controller in town is a step in advance compared to the induction AC motors employed traditionally, or DC brushed motors which became a trend 10-15 years ago, there are many marketing promises as: "high torque at all speeds", "variable speed advantage without changing gears", which are not always what yo get when you replace your AC induction motor by a DC brushed or BLDC (Brushless DC) motor. Maybe after reading my prepared speech you will be able to understand that different controllers cost have a correlation with different performance as servo axis motor or spindle motor in your machine, and how to analyze, based on the controller manual programming options, if the vendor is inflating the cost but giving you an inferior product disguised as a servo or "idealized" spindle marvel.

I gave up on my speech when I saw the following video, it saved me a lot of time, and it saved you from a lot of reading and photos. It is important for CNC users to understand the implications of a term used in the video: "Torque Ripple" , since it influences the finished surfaces of the machined parts and the vibrations induced in the machine tool. Here is the video:

https://www.youtube.com/watch?v=InzXA7mWBWE

[kreutz]

Let's start with a block diagram description of the future BLDC motor controller.
It will need:
- Power cord receptacle
- Line EMI and common mode noise filter
- Bridge rectifier
- Inrush current Limiter
- Capacitor bank (could be only one capacitor, Two capacitors in series connection, or a real capacitor bank composed of more than two capacitors in series/parallel) depending on the final output power limit for our design.
- Output 3 phase bridge (discrete IGBts, or Integrated power module)
- Phase voltage sensing (resistor dividers, filtering and ESD protectors)
- DC link Voltage sensing (resistor divider, filtering ). Having a DC link voltage sensor allows us to compensate (in software) for the line ripple voltage (which affects "torque ripple") and also protection against DC link over-voltages due to sudden braking an inertial load by using freewheeling or synchronous/quasi-synchronous rectification in the output 3 phase bridge. we will discuss this situation later. This software compensation will allow us to reduce the total DC link capacitance a 20-25% with respect to the traditional designs which calculate the total capacitance based on a 5% - 10% voltage ripple at the output. Dc link capacitance will also be influenced by the motor braking method employed in our design.
- External interface to an external brake resistor (optional)
- 3 phase bridge gate drivers (either individual half bridge drivers or integrated 3 x half bridge drivers.
- Motor coil(s) current sensing and amplifier(s) (could be one or two sensor/amplifiers)
- Microcontroller (requirements depend on the commutation method(s) employed in our design)
- External control interface(s) and the need to electrically isolate the interface from the board's ground, including also the PC communication interface for setup/tuning.

All of the above will be calculated based on our BLDC motor and the data sheets of the components used, Motor parameters will be previously identified using the evaluation boards. So at the time of designing the final pcb those parameters will be known to us. They are required for both, the software and hardware design.

[kreutz]

No news, my daughter is moving and all the clutter got its way into the workshop.

[kreutz]

Merry Christmas and a very Happy and Prosperous 2023 for everyone!!!
All my work is on hold, still have many unfinished projects but they will be left for 2023. My workshop is a real mess and there is still some water damage left from the last hurricane. Luckily is only cosmetic, but some sheetrock boards from the ceiling will have to be replaced as soon as the clutter is gone.

Best regards!
kreutz

[dmderev]

Hello,
Does anyone have the schematics or at least pinout of the connectors? This one has a good "contactless" voltage control on the pedal (based on analog Hall effect sensor), but are there any other active pins on the 6-pin pedal connector?