DIY BLDC / DC Motor Servo Drive - ARM MCU (STM32F103C8T6)

[jimmkaz]

KOC62,

There are literally thousands of people using the Gecko G540 with steppers very successfully. Why squander money if you don't need to?
By the time you build what Websrvr is promising you might be out of business. Right now it's just conjecture with no proof of concept.

I currently have 4 steppers, nema23, -- http://www.automationtechnologiesinc...kl23h286-20-8b and a Gecko G540 that is working just fine.
What would be the equivalent in a BLDC motor of nema23 size? It appears to me that any BLDC is going to cost a lot more with little return in my scenario. Or do you see a significant benefit?
Maybe I just need to add an encoder to my stepper and get good results, as a wannabe BLDC?

[jfong]

I currently have 4 steppers, nema23, -- http://www.automationtechnologiesinc...kl23h286-20-8b and a Gecko G540 that is working just fine.
What would be the equivalent in a BLDC motor of nema23 size? It appears to me that any BLDC is going to cost a lot more with little return in my scenario. Or do you see a significant benefit?
Maybe I just need to add an encoder to my stepper and get good results, as a wannabe BLDC?

It would be very difficult to choose a BLdc motor without knowing your machine specs. You need to know

All leadscrew pitch
Machine weight for each axis. If you have a gantry cnc, how heavy is it. This is used to calculate your required acceleration.
Do you want pulley reduction or direct drive. If pulley reduction, what ratio.
The required maximum feedrate.
How much cutting force is required for each axis. Cutting metal usually requires more than wood.

Probably a few things I forgot to list but there really isn't some easy way to say that this servo motor is equivalent to that stepper. A servo motor of equivalent size to a stepper will have lower torque but run at much higher rpm. This usually requires some kind of gearhead or pulley reduction to utilize a servo motor to its fullest potential.

[websrvr]

I spoke to the motor specialist this morning, he says DC induction motors exist, in one design considered to be the most commonly used, the use of an exciter coil to start the flux conversion process is required because the transfered flux generated by the electromagnetic energy from the stator is insufficient to start the motor turning but sufficient enough to keep it turning.

Some require a separate excitation power source and others use the existing stator power source and generate/create the excitation power source, he also says this common type typically operate at a voltage of 400VDC to 600VDC, he further explained that unless your looking for massive power and minimum on times of > 1sec without direction changes such as conveyor systems and this type of motor is not really suitable for servo applications used in machining equipment.

Another design not so common has it's own flexible PCB inside which contains the components to take a lower stator voltage and create a higher voltage for excitation which is constantly applied but is also not suitable for servo applications due to the high starting current requirements, I have one of these motors and I was hoping to convert it to a servo motor so that's now out the window cause he said it wont work as a servo motor.

This kinda sucks cause I was thinking it would be nice to make a small induction motor specifically for this driver but he says without major changes and a costly motor design it wouldn't be possible in such a low voltage application to do it efficiently or inexpensively.

He also told me that some of the other motors I have which are AC/DC motors have both a squirrel cage and magnetic material but are not considered induction motors because of the magnetic material and operate at much higher RPM but induction is used at the higher RPM (above 4000) to offset the flux loss due to gravitational magnet force loss and this confuses me because magnet force I thought was constant based on it's material so how can it be affected by rotating it, not as simple as I thought it was.

On the weekend when I'm assembling my asynchronous servo spindle motors he'll have some drawings I can examine that shows the internals of a DC induction motor made for Georgia Pacific (I think they're a lumber company) and I'll get a more detailed explanation of the principles and technology involved.

[KOC62]

OK, here is where I'm at.

I don't have a BLDC motor nor the parts to make mihai's controller. I have minimal code skills, but can learn the missing pieces.
For me to invest in this kind of project, I would want at least a BLDC motor size to replace a nema23 425oz-in stepper motor.
Currently it doesn't look like I can get all this stuff (parts, board, motor) for under $100 to tinker with so I'm inclined to just watch this thread.

[websrvr]

This topic is about an inexpensive open source motor controller to drive a BDC or BLDC motor, what good is the motor controller if there is no inexpensive motor to drive so a discussion abut motors is relevant, just wish I know more about what is the appropriate type and specifications and not having to rely on others to determine this.

Fortunately I have access to someone who is producing a suitable motor and he tried to help develop this project but it didn't work to yours or anyone else's favor because he's been denied permission to be here to work on it so he developed for his own use which means pretty much everyone except a small select few can't benefit.

I know him and I'm not on any bad terms and he wont share his code with me and I can understand his reason why, it's commissioned work so it's not available.

I tried to assist in developing this open source project here and YOU didn't want me to and mainly your efforts seem to only be in derailing the project, stopping/preventing development and attacking people.

Now I've got a driver and access to BLDC servo motors and my cost is about $95.00 an axis, since I'm making drivers for myself I thought I would look at the possibility of making an inexpensive motor to go with it and share it if I could do it cheap enough, I was thinking "be different" and do DC induction however, this has been deemed a poor choice for the application for many reasons and as I look further into producing a motor, it is doubtful I can produce one for less than dwalsh62 does cause I can't do his quantity so I'll be buying them from him unless a cheaper source becomes available because I can't see an open source project that isn't being openly and publicly developed require a motor that can only be produced cheaply in volume when the project doesn't appear to be under any public development.

When I look at the cost of cheap Tamagwa copy encoders starting at $25.00, I can't see how dwalsh62 makes a motor using a real Tamagawa encoder because they start at $75.00 for a non quadrature A/B type to $300.00 for a 10K RPM quadrature A/B/Z + HALL U/V/W/A/B/C.

You can't make less than three boards and the cost is $90.00 plus shipping from OSH Parks, you can't get a stencil for less than $75.00 and I advise against the non metal type so think more like $100.00, you can't buy the parts for three boards for less than $179.00, retail pricing sucks and parts for 100 board is considered a joke in a quantity purchases.

You can start development on a breadboard but eventually you're going to need to make a board to complete and finalize the development and these usually come at the expense of the developer.

Yes, $35.00 without fets for a small board sounds expensive to some but this is still way less than the cost of the included parts when making 50 boards, I'm told that a normal production run of typically 10,000 boards, the cost could be reduced to less than $20.00 a board and this sounds really great but where would I get $200,000.00 to make this run and where would I store 10,000 boards.

To think that Mihai will return if you ask him nicely enough is a fantasy, what I've read in this thread and his responses to me indicate it to be true that it was a school related project, for him this project was an educational exercise to gain a credit or two, the quality about the design wasn't as important as making something work to gain the credit, it's served it's purpose and he's moved on, unless he gets an additional credit for making it work right he has no interest in revisiting the project as it's served it's purpose and he's now on to bigger and better things and I wish him luck.

I'm personally glad he started it, it gave me a foundation to take it to the next level, on my own I probably wouldn't have tackled such a project but with 75% of the work done and an update electrical design done by the MCU manufacturer I concluded it was worth the effort to learn what I needed to which took about four or five weeks.


Sensibly thinking I hope you choose to rise up to the challenge, with bias I hope you don't and wish only to see you go splat as you hit the pavement hard from the failure, a real dilemma you have placed me in, wish the project well or wish you failure, if I wish for your demise the project dies as no one is jumping in to get it back on track and promote it's development including you.


I'll go one step further and increase your chances of success as a real leader but think the offer will be rejected unless you've grown a backbone or decided to make the best of a bad situaiton you have placed yourself in.

The serious offer, for the cost of shipping, I will send an STM32F103TBU6 developer board (I have a small supply I no longer need since I'm done developing that I can send to a couple of developers) so that the developer(s) has the target MCU platform to do the development work on, all you need to do is find him/her.

I wont even question if this is a task you're capable of or if you will offer excuses that you're not the project leader and further hurt your credibility because you represented yourself as the project leader when you made some critical decisions that had a serious impact on the project, your decision or lack of, will be a deafening response that says everything about you and your character and will have a great affect on how people will perceive your future contributions as worthy or wasteful so I advise you to take the time to seriously consider what is being offered and in the best interest of the project before making any decision.

So, it's really on you now, what do you want to do with this project because everyone considers you to be the project leader (for reasons stated) and they are waiting on you to find out where it's going.

[jimmkaz]

websrvr,

Are you asking me or the group if your contribution to this thread is productive?
Are you asking me or the group if the thread needs a project leader?

[ger21]

This thread is about 1 more post away from being closed. If I had to bet on it, I'd say it has about 6 hours left, max.

[jimmkaz]

websrvr,

If in fact you fail at anything it will be no fault of mine.
If the group wanted a leader don't you think by now they would have spoke up and elected someone other than Mihai.
Why is the belief that Mihai is returning a fantasy?
Maybe the reason he is not here is because he believes your presence is polluting the thread.

[websrvr]

If Mihai thinks I am polluting the thread and my presence unwelcome he has had plenty of opportunities to inform me of this.


Brad43, I advise you not to argue or respond to anyone, you don't need to be anyones white knight and certainly don't need to become involved in any bickering when it's decision making time.


jimmkaz, don't you get it, you assumed this role role of leadership, you made decisions you claimed were in the best interest of the group and project, everyone believes you are in charge because you represented yourself this way.

I see two potential people who would be willing to work on the code, one I would probably go out of my way to aid because I see he's trying and a third who would probably join in if/when he sees that it's worth his time and the circus show is over.

ger21 has made a valid decision regarding his potential action with respect to this thread, the bickering needs to end and to that my offer stands, act like a leader and make decisions in the projects best interest or do nothing and let it die but at least be a man and make your decision publicly known to the group because they are counting on you.

Bottom line, everyone is looking to you to continue the leadership role you assumed, surely you didn't take control just to get rid of me then quickly discard it leaving it in a bad state.

I'm not part of this group or project, I think it's a valid project and I may choose to contribute to specific individuals as I see fit but no one has the right to contact me demanding I post my source code claiming it belongs to the project, I worked on no project with anyone, I'm not distributing any code to anyone, it belongs to me and is mine to use as I see fit and don't owe anyone anything except acknowledgment that Mihai was the original creator and I thank him for his contribution.

It is unfortunate you didn't consider this when you assumed the role of leadership you unjustly claimed so stop trying to shift focus from your self appointed leadership to one in which the group needs to be consulted, you claimed control, you made a decision which you publicly stated was in the best interest of the group and project without actually consulting the group so don't claim the group now needs to be consulted, they all think you're in charge, start making decisions in your attempt to keep the project alive or make decisions and take actions to find suitable leadership that can, the group is relying on you as their leader, if you're not willing to do this then at least have respect for those in the group and request ger21 close the thread.

[jimmkaz]

websrvr,

What does leadership have to do with contributing to this thread?
Maybe whoever is contacting you for firmware believes you stole or misappropriated it.
The moderators are threatening to close the thread because it may no longer be contributing to the Open Source commitment to which it serves.
Your posts offering to sell untested incomplete products are not benefiting anyone here except yourself.
You should be a man and start your own thread, using your own work instead of riding on the back of Mihai.
Your claims have done nothing but slander and belittle Mihai.
Why not stop pretending and man up?

[Khalid]

Ger21,
Unfortunately, it seems to me a great conspiracy in regard to closing this valuable thread. Better the thread remains open but the guys who are troublemaker (including me if i am responsible) to be banned.

[mcm_xyz]

Hello guys

This thread has become a really nice mess... However, I have to state again, I can not work on this project anymore, I do not have time for this. The source code and schematic I made are free for everyone to use as they think is fit to them, they can modify and not publish it, they can build commercial things if they want.
My only regret is that I did not see real progress on this project.

Mihai