trying to get a 3 pin brushless motor going

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trying to get a 3 pin brushless motor going

Postby Harry Dalek » Sun Oct 13, 2013 11:01 am

Bit of a pain with my last pc power supply dying spent the last 2 days converting it to a transformer version arrr i have a dual power supply again ....
But on the 555 timer i have been working on a circuit Hard drive brushless motor they have a nice amount of speed if you can get them going seeing if i can use that for the current project.

My clock is once again a 555 it works for a while then stops had me beat then i saw i had forgotten the cap on pin 5 to ground you got about a minute or 2 of it working fine then it slows down and stops .

I will report back if i have any luck with it .

BTW i did end up buying that laser printer Gary i have not tested it for NBTV but the wife is sure happy with it.....lets hope it'll put a smile on my face when i get around to printing out an encoder .
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just needed a quick classic dual power supply
took me 2 days track down parts and solder away
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The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby M3DVQ » Sun Jan 12, 2014 4:23 am

bizarre coincidence!

I just logged on to mention that I've been playing with a hard drive motor today!

(my motor is three coils in wye configuration which seems to be the most common - I also have a floppy drive motor that I've wired up leads directly to the coils so I can play around trying bot wye and delta with that)

I have the motor running reliably at 12.5 revolutions per second, off pulses generated from an atmega attiny, switching power transistors or a big dual H bridge chip (just used as three power transistor outputs not as an 'H').

With no closed loop feedback and just connecting the drive pulses to the motor it obviously isn't self starting. What I have gleaned from the internet is that in a hard drive the motor control just ramps up the speed of the rotating magnetic field at power on and there is no feedback. How true this is I don't know, but I implemented that in my quick and dirty microcontroller code and can indeed spin the drive up to 750rpm from stationary. :D

I confirmed that everything was running stable at the right speed by sticking a bit of sticker to the hard disk platter and looking at the output of a reflective opto sensor on the 'scope. Touching the centre of the spindle to slow the motor slightly it returned locked back to exactly 750rpm within two or three seconds (a little hunting either side) :D

Once I had all this working I printed off a nipkow template on some A4 card and attached that, and with a spare output on the microcontroller pulsed an LED to shine through. This way I could find a black/white transition and see how stable the speed was visually.
The answer unfortunately was not very. By adding a floppy cardboard disk and more than doubling the diameter the motor is more reluctant to start, heats up more, and just moving or breathing near the disc makes the image wobble back and forth. :?
This would be improved a bit by a more accurate and stiffer disc as I expect running the disc in an enclosed cylinder like the hard disc itself would.


The last thought on the subject before I switched everything off for the evening though is the issue of synchronising the rotation to the frame.

The way my particular hard drive motor is constructed the coils have to be pulsed round in sequence four times for one rotation of the motor, so in other words if instead of just a rough square wave my driver produced three sinusoidal waves 120 degrees out of phase it would take four cycles to complete one revolution.
If we generate the three phase waveform synchronised to frame sync pulses obtained from the video input the motor will be running locked to the correct speed but phased either 0, 90, 180, or 270 degrees from the frame sync.
To determine this phase would require some feedback pulses from the disc and to do anything about it the disk must be allowed to run at the wrong speed and drift around until in phase at which point you're back to all the same problems of a DC motor and closed loop speed control. :roll:
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Postby Harry Dalek » Sun Jan 12, 2014 1:40 pm

M3DVQ wrote:bizarre coincidence!

I just logged on to mention that I've been playing with a hard drive motor today!


I was playing with the idea a little while back try and make some use of the things ,i never got back here but i did get it going but i was not happy with the speed and some times i had to kick start it .

(my motor is three coils in wye configuration which seems to be the most common - I also have a floppy drive motor that I've wired up leads directly to the coils so I can play around trying bot wye and delta with that)


I am pretty sure what i was playing with was a 3 wire one too.
I just tried the old Hard drive type .

I have the motor running reliably at 12.5 revolutions per second, off pulses generated from an atmega attiny, switching power transistors or a big dual H bridge chip (just used as three power transistor outputs not as an 'H').


I used the old 555 then 4017 then a H bridge chip was well it sort of worked ,not as good for me as using the same sort of idea for a stepper motor ...i can't remember how fast it went but i recall changing the pulse width on the 555 helped as well if you haven't tried that yet .

With no closed loop feedback and just connecting the drive pulses to the motor it obviously isn't self starting. What I have gleaned from the internet is that in a hard drive the motor control just ramps up the speed of the rotating magnetic field at power on and there is no feedback. How true this is I don't know, but I implemented that in my quick and dirty microcontroller code and can indeed spin the drive up to 750rpm from stationary. :D


Thats much better than i have never tried and thats something i have never done or looked into .
I can only think with no feed back control you are increasing the frequency and pulse widths via that code.

I confirmed that everything was running stable at the right speed by sticking a bit of sticker to the hard disk platter and looking at the output of a reflective opto sensor on the 'scope. Touching the centre of the spindle to slow the motor slightly it returned locked back to exactly 750rpm within two or three seconds (a little hunting either side) :D


Wow thats spot on that idea with come in useful ! that will make one good Nipkow motor .

Once I had all this working I printed off a nipkow template on some A4 card and attached that, and with a spare output on the microcontroller pulsed an LED to shine through. This way I could find a black/white transition and see how stable the speed was visually.
The answer unfortunately was not very. By adding a floppy cardboard disk and more than doubling the diameter the motor is more reluctant to start, heats up more, and just moving or breathing near the disc makes the image wobble back and forth. :?


OH I was going to say what would a smaller disk do if it has something to do with the extra mass but sounds like it is a tiny disk ..the old HD platter would make a great disk ..wonder why it heats up with such a small extra mass on it ? should be able to handle more than that .
I didn't like having to kick start mine

This would be improved a bit by a more accurate and stiffer disc as I expect running the disc in an enclosed cylinder like the hard disc itself would.



When i ever used them i kept them in the case and used the platters ,...before i tried driving them i just used a pulley system to a dc motor just used them to hold the platters and or record nipkows

The last thought on the subject before I switched everything off for the evening though is the issue of synchronising the rotation to the frame.


ARRR interesting idea

The way my particular hard drive motor is constructed the coils have to be pulsed round in sequence four times for one rotation of the motor, so in other words if instead of just a rough square wave my driver produced three sinusoidal waves 120 degrees out of phase it would take four cycles to complete one revolution.


I might get mine out again and look into that more than likely a good idea for a normal stepper motor



If we generate the three phase waveform synchronised to frame sync pulses obtained from the video input the motor will be running locked to the correct speed but phased either 0, 90, 180, or 270 degrees from the frame sync.
To determine this phase would require some feedback pulses from the disc and to do anything about it the disk must be allowed to run at the wrong speed and drift around until in phase at which point you're back to all the same problems of a DC motor and closed loop speed control. :roll:
[/quote]

Well they are always going to be a pain trying to sync but getting them going to the point you have is more than half the battle ..Nice experiments !
When i get around to getting mine out again see if i can convert it .
Again great work :wink:
Last edited by Harry Dalek on Tue Feb 09, 2016 5:33 pm, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby M3DVQ » Mon Jan 13, 2014 2:49 am

Harry Dalek wrote:I used the old 555 then 4017 then a H bridge chip was well it sort of worked ,not as good for me as using the same sort of idea for a stepper motor ...i can't remember how fast it went but i recall changing the pulse width on the 555 helped as well if you haven't tried that yet .

same sort of thing but using the microprocessor just makes it quicker to throw the circuit together then experiment in code rather than re-calculating the components for a 555 circuit :)

Thats much better than i have never tried and thats something i have never done or looked into .
I can only think with no feed back control you are increasing the frequency and pulse widths via that code.

Yes, I start off with something like 50 milisecond pulses and loop round decreasing the delay length by 200 or something each time until the delay is at 6666 microseconds iirc
It's all very quick and dirty code with values for the acceleration just pulled out of thin air, what seemed to work.
If you start too slow it just sits there bobbing about for ages before it starts to spin, and if you ramp up too fast it gets left behind and rolls to a stop.

OH I was going to say what would a smaller disk do if it has something to do with the extra mass but sounds like it is a tiny disk ..the old HD platter would make a great disk ..wonder why it heats up with such a small extra mass on it ? should be able to handle more than that .
I didn't like having to kick start mine

The disc is something like 7" diameter so it's at least doubled the diameter and only being printer card it's not very flat so adds loads of air resistance.
The heat is probably because I just have the motor blue tacked to the desk, it's not bolted to a big lump of aluminium any more - having said that I've known hard drives get uncomfortable to touch when run up constantly too.
I would want to reduce the load on before I tried to use it for a televisor though.
As I say, I imagine a stiff metal disc inside suitable airtight enclosure would run very smoothly but that's beyond my fabrication abilities.


Well they are always going to be a pain trying to sync but getting them going to the point you have is more than half the battle ..Nice experiments !
When i get around to getting mine out again see if i can convert it .
Again great work :wink:


Before I really looked into hard disk motors I had it in my mind that a synchronous motor solves all our problems. Just generate power waveforms based off the incoming syncs and voila, the disk just has to run at the correct speed and phase.
No doubt this would be true for a motor with just six coils and a 2-pole magnet but alas using floppy drive or hard disc motors it's not as simple as all that.

What I do have as I mentioned is a floppy drive motor (which are larger) already disassembled. What I may try is removing the ring magnet and making a rotor with just two poles, then re-wiring the stator and building a six phase power supply :shock:

I also suspect that the floppy motors are much more powerful than hard drives (hence the larger size) because they have to run against the drag of heads on the floppy disk unlike a hard drive motor that has almost no load to speak of.
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Postby M3DVQ » Mon Jan 13, 2014 3:23 am

just hooked a floppy motor up to my driver with no changes and my suspicions are correct. It's vastly more powerful than the hard drive motor at these low speeds.
It's spinning my 7" card disc just helf on with blu-tak and I can blow on it, touch things against it, etc and it really doesn't want to lose lock. I wish I could demonstrate it, but I doubt I could hold my camera and the LED still enough to capture the edge of the pulse I'm seeing through the nipkow.

Still the same phase problem of course as this motor is the same configuration as the hard drive motor, just physically larger.
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Postby M3DVQ » Mon Jan 13, 2014 4:57 am

here's where I am right now:
Floppy motor running at 12.5 revolutions per second with a floppy card nipkow disc.

Image

and a wobbly video: http://www.taswegian.com/NBTV/forum/fil ... or_193.mpg

The 'scope is displaying the output of a reflective opto sensor positioned so that it 'sees' a bit of sticker on the rim of the disc go past on every revolution. This confirms that the disc is running at the right speed.

The LEDs are flickering in time with one of the motor drive pulses and thus provide a pattern which simulates a video signal locked to the motor control.

In the video I touch the disc a couple of times to slow it down and let it re-lock.
Attachments
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Postby Harry Dalek » Mon Jan 13, 2014 7:16 pm

M3DVQ wrote:
same sort of thing but using the microprocessor just makes it quicker to throw the circuit together then experiment in code rather than re-calculating the components for a 555 circuit :)


Thats one place this harry has never gone before never tried that side of electronics at all ...perhaps i am stuck in a rut i do like that 555 timer .
BTW i did see a circuit that just got all the pulses to drive one of these things with one 555 circuit looked a bit iffy to me .


Yes, I start off with something like 50 milisecond pulses and loop round decreasing the delay length by 200 or something each time until the delay is at 6666 microseconds iirc
It's all very quick and dirty code with values for the acceleration just pulled out of thin air, what seemed to work.
If you start too slow it just sits there bobbing about for ages before it starts to spin, and if you ramp up too fast it gets left behind and rolls to a stop.


It drove me nuts how fussy it was starting up and the old stepper motor problem trying to do it to quick rotten thing stops .
I wonder if i should of had a dual pot with frequency and pulse width adjustment on the same shaft as a primitive way to copy your modern ways :wink:


The disc is something like 7" diameter so it's at least doubled the diameter and only being printer card it's not very flat so adds loads of air resistance.


Oh yes i see it in your video and thanks for posting btw it every little bit of information helps ...So that was a floppy motor test .
I was going to try and just cheat and use the HD drive electronics but they cut out after a few seconds of start up .
I could not be bothered trying to track down via all that electronics what would over ride it to keep it running ....i should think if you could there might be one of 2 ways to try and control the speed ...but like you i would rather start from scratch and use my own electronics .

The heat is probably because I just have the motor blue tacked to the desk, it's not bolted to a big lump of aluminium any more - having said that I've known hard drives get uncomfortable to touch when run up constantly too.


Well thats a good reason and its some thing i never thought about much so there is a reason hard drives are in that metal case !

I would want to reduce the load on before I tried to use it for a televisor though.
As I say, I imagine a stiff metal disc inside suitable airtight enclosure would run very smoothly but that's beyond my fabrication abilities.


Why don't you just use the Hard drive's case ? and a platter you have the motor going the hard part is done...do you have a Dremel tool ? you get little tools for it like tiny grinder disks .
I have cut the case of a HD many times you could cut or just use a normal drill for a hole behind the case so you could use the platter as a Nipkow ,the image will be pretty tiny with a disk that size but with magnification it will work.
Even better a out of focus laser and you can project it to a nice size .


Before I really looked into hard disk motors I had it in my mind that a synchronous motor solves all our problems. Just generate power waveforms based off the incoming syncs and voila, the disk just has to run at the correct speed and phase.
No doubt this would be true for a motor with just six coils and a 2-pole magnet but alas using floppy drive or hard disc motors it's not as simple as all that.


Its much harder using these motors for sure but you have a leg up on the rest of us, i have not heard of any one really using them might be wrong but not on the forum any way.

What I do have as I mentioned is a floppy drive motor (which are larger) already disassembled. What I may try is removing the ring magnet and making a rotor with just two poles, then re-wiring the stator and building a six phase power supply :shock:


Oh it might work if you do it do show us,i am a bit lazy to pull motors to bits .
A lot of these motors will be gone in the years to come mechanical storage devices will soon be dead ,i expect a few years of junk shop finds then who knows .

I also suspect that the floppy motors are much more powerful than hard drives (hence the larger size) because they have to run against the drag of heads on the floppy disk unlike a hard drive motor that has almost no load to speak of.
[/quote]

More than likely right there but the other does go faster ....wonder how fast floppy disks went .

I like the idea of the Hard drives just because of the speed they can do may be one day i can learn to drive them like you ,show us any other tests i find it interesting .
Last edited by Harry Dalek on Tue Feb 09, 2016 5:34 pm, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby M3DVQ » Tue Jan 14, 2014 12:30 am

Harry Dalek wrote:Why don't you just use the Hard drive's case ? and a platter you have the motor going the hard part is done...do you have a Dremel tool ? you get little tools for it like tiny grinder disks .
I have cut the case of a HD many times you could cut or just use a normal drill for a hole behind the case so you could use the platter as a Nipkow ,the image will be pretty tiny with a disk that size but with magnification it will work.

If you can devise a way to accurately make a nipkow from a hard drive platter I'll take two ;)

Harry Dalek wrote:Oh it might work if you do it do show us,i am a bit lazy to pull motors to bits .

I am reluctant to spend too much time on rewiring a motor because it veers away from the ideal of re-purposing a useful scrap motor part.
If I could create control electronics to overcome the phase issue then that's less soldering. :)

Harry Dalek wrote:A lot of these motors will be gone in the years to come mechanical storage devices will soon be dead ,i expect a few years of junk shop finds then who knows .

Well I'm amassing quite a stockpile, same with CD drives :)

Harry Dalek wrote:More than likely right there but the other does go faster ....wonder how fast floppy disks went .


300 rpm. They seem to have plenty of power left in reserve at 750 though as I demonstrated.
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Postby Harry Dalek » Tue Jan 14, 2014 3:19 pm

M3DVQ wrote:If you can devise a way to accurately make a nipkow from a hard drive platter I'll take two ;)


Bit harder to make the holes but the old trick of using a bigger hole and having a movable tiny hole on something easier to make hole on for the size and glue it over the big hole ,move it around and test before its left to dry in place...might be a way i think Andrew tried that years ago ?
Does not matter if its not a laser hole cut disk i think its more impressive doing your best than buying accuracy theres no pride in that .

I am not sure of the size difference but a cd or dvd just off hand now might be a touch bigger i am guessing ,might be an idea to grind them to size to fit in that case or cut a slot in the case perhaps , well they are easy to convert to a nipkow ....a hot pin will make a hole like a hot knife in butter.
i have used cd or dvds on hard drives many times .



I am reluctant to spend too much time on rewiring a motor because it veers away from the ideal of re-purposing a useful scrap motor part.
If I could create control electronics to overcome the phase issue then that's less soldering. :)


Its a good idea it might work but yes if it doesn't there gos the motor,i am not good at that sort of thing so i would not try it


Well I'm amassing quite a stockpile, same with CD drives :)
[/quote]

Might be an idea to collect a few while you can floppy drives are hard to find like 5inch ones with the steppers are long gone my way .

Btw dvd players come with a very nice little DC if you ever come across those i like the dvd clipping on part makes using changes Nipkows easy .
Last edited by Harry Dalek on Tue Feb 09, 2016 5:34 pm, edited 1 time in total.
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby AncientBrit » Wed Jan 15, 2014 7:04 pm

I recently scrapped a lap top and wanted to disable the hard drive.
I opened it up and tried to use a screw driver to bend the platters.

What I didn't realise is that the platters were made of glass with a thin deposit of magnetic material.

Bits flew everywhere, I was lucky they missed my face.

The point I'm making is that to drill Nipkow holes may not be possible if the larger hard drives use the same construction.

Regards,

Graham
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Postby Harry Dalek » Wed Jan 15, 2014 10:50 pm

AncientBrit wrote:I recently scrapped a lap top and wanted to disable the hard drive.
I opened it up and tried to use a screw driver to bend the platters.

What I didn't realise is that the platters were made of glass with a thin deposit of magnetic material.

Bits flew everywhere, I was lucky they missed my face.

The point I'm making is that to drill Nipkow holes may not be possible if the larger hard drives use the same construction.

Regards,

Graham


Thats a new one on me Graham !
Every Hd i have a platter from is metal no glass ,you would think thats a bad idea to make them from glass...suppose they saved on metal but yakes !
The electromagnetic spectrum has no theoretical limit at either end. If all the mass/energy in the Universe is considered a 'limit', then that would be the only real theoretical limit to the maximum frequency attainable.
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Postby AncientBrit » Wed Jan 15, 2014 11:34 pm

Hi Harry,

The laptop was fairly ancient, mono plasma display.

I suppose about 20 years old.

Cheers,

Graham
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