New Drum monitor build

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Postby gary » Wed Feb 15, 2012 7:57 pm

harry dalek wrote:Gary its one resistor for the stepper yes not a resistor for each coil ? i did it wrong if so .


Harry I had to think about this one because when I built my circuit I had a BIPOLAR arrangement whereas you are using a UNIPOLAR arrangement, in which case the arrangement is slightly different.

In any case the answer is that the resistance has to be in series with each coil. However, as only one coil of a pair are energised at any one time the resistor can be in the common of that pair. Hence only two resistors are needed.

I will have to refer to my notes to double check there are no other issues pertaining to unipolar arrangements
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Postby Harry Dalek » Thu Feb 16, 2012 12:28 am

gary wrote:
harry dalek wrote:Gary its one resistor for the stepper yes not a resistor for each coil ? i did it wrong if so .


Harry I had to think about this one because when I built my circuit I had a BIPOLAR arrangement whereas you are using a UNIPOLAR arrangement, in which case the arrangement is slightly different.

In any case the answer is that the resistance has to be in series with each coil. However, as only one coil of a pair are energised at any one time the resistor can be in the common of that pair. Hence only two resistors are needed.

I will have to refer to my notes to double check there are no other issues pertaining to unipolar arrangements


OH ok i have not tried that !

I will give that a go gary thats something i have not tried thanks for that.

I will have to look into my light modulation circuit i can see its failing more than likely due to the little transistor i am using i am driving the luxeons i can just see a slight modulation now so i will look into that tomorrow .

Due to this i can not tell how well the motor and stepper idea works with am image but i did the test tonight ..i can tell you that clogging still happens even with the DC motors help which might be the frequency its working at i'd be interested to see what happens at a frequency that it couldn't run at what effect it has with the DC motor ,i was thinking it would be the other way around but it looks better to adjust the dc motor to correct the stepper speed ,i really have to see an image before i can tell how well either motor control adjustment works best but so far i like the dc speed controlling the steppers .

So a little frustrating results with the modulation problem .
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Postby gary » Thu Feb 16, 2012 9:14 am

I do think that you will probably always get cogging using this kind of driver circuit although I had hopes for the DC motor arrangement. I, as previously discussed, used sine waves rather than rectangular pulses to drive a bipolar stepper. This is easy enough to arrange as a test as you can use your PC to generate the required waveforms. It is not quite so easy, however, to amplify these waveforms unless you have access to a suitable power amplifier or can construct one.
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Postby Harry Dalek » Thu Feb 16, 2012 3:24 pm

gary wrote:I do think that you will probably always get cogging using this kind of driver circuit although I had hopes for the DC motor arrangement. I, as previously discussed, used sine waves rather than rectangular pulses to drive a bipolar stepper. This is easy enough to arrange as a test as you can use your PC to generate the required waveforms. It is not quite so easy, however, to amplify these waveforms unless you have access to a suitable power amplifier or can construct one.


Hi Gary

I suppose its ok up to a limit but trying to better this does cause it to fail and you need to reset.

Yes theses stepper motors are tricky sounds like you just about need a PC to control the things right.

i was thinking before hand it wouldn't clog with the dc motors help but it still does when you push the speed DC motor or not .

funny reverse didn't effect it as i was expecting either i was expecting it to brake the dc speed but it tends more to be no real effect to the dc's speed but when you change to the same direction of the dc motor it does help speed....as far as being useful i am not sure yet .

I expect there to be less drift with an image and seems to control speed in a spread out way where as just using as you know a dc motor speed control is tight.

The dc seems to have a nice speed but any more on the above i need to see something so on to checking out the luxeon circuit today .
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Postby gary » Thu Feb 16, 2012 3:40 pm

harry dalek wrote:I suppose its ok up to a limit but trying to better this does cause it to fail and you need to reset.


Sorry Harry, what does that refer to? Is that the result of your test?

harry dalek wrote:Yes theses stepper motors are tricky sounds like you just about need a PC to control the things right.


Well there would be very few applications of a stepper where a computer or microcontroller isn't involved. Having said that, you only need a source of mains AC (through a transformer of course) and a capacitor and you have a stepper turning at 250/300 RPM. It couldn't be simpler. The problem is you are trying for 1500 and with these little floppy steppers it's a big ask - but I didn't say impossible!
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Postby Harry Dalek » Thu Feb 16, 2012 6:59 pm

gary wrote:
harry dalek wrote:I suppose its ok up to a limit but trying to better this does cause it to fail and you need to reset.


Sorry Harry, what does that refer to? Is that the result of your test?

harry dalek wrote:Yes theses stepper motors are tricky sounds like you just about need a PC to control the things right.


Well there would be very few applications of a stepper where a computer or microcontroller isn't involved. Having said that, you only need a source of mains AC (through a transformer of course) and a capacitor and you have a stepper turning at 250/300 RPM. It couldn't be simpler. The problem is you are trying for 1500 and with these little floppy steppers it's a big ask - but I didn't say impossible!
[/quote]


Gary Yes when you run the stepper and dc together it seems to me to be about the same place the stepper fails clogs at in the adjustment but it must be going faster due to the the DC speed looks like it helps in speed when stepper is going as well .....both speed adjustments control each other but i find the Dc one is better ,its a slow or nice spread out controlled braking .

Normally when you cut back a DC motor you sort of over shoot because its hard to control but seems very controlled when the stepper is going ..so i like that part ...Just the stepper clogging thing which mostly happens pushing top speeds.....

I might just be better to run a stepper slow and gear or pulley it up to the right speed ...but as i found out gearing for us is a no no ....my simple pulley would need something small single record sized which would give at least around 10 times the speed ,1500rpm is hard with a stepper but as you say not impossible.
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Postby gary » Thu Feb 16, 2012 7:12 pm

Hi Harry, the way I would have thought you would do it is to run the DC motor up to just above synch speed. The stepper would be unpowered up to that point, and then you would cut the stepper in at the sync speed rate. It's control signal, ideally, would be derived from the video sync stream.
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Postby Harry Dalek » Thu Feb 16, 2012 8:35 pm

gary wrote:Hi Harry, the way I would have thought you would do it is to run the DC motor up to just above synch speed. The stepper would be unpowered up to that point, and then you would cut the stepper in at the sync speed rate. It's control signal, ideally, would be derived from the video sync stream.


Gary i was sort of trying to do that but my modulator has failed the transistor that drives the luxeons so i was more looking number of lines because of that since i couldn't do the other yet it led to working out a problem .

Frustrating while testing and something i should of known better since working it out on the last one ,i need to also redo the small drum slits ,i was forgetting i need them to match the length of the slanted slits in distance between the small drums straight slits ....i just copied my last drum slit number without thinking of size problems ,i could slap my self :evil:
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Postby Harry Dalek » Sun Feb 19, 2012 5:12 pm

First free time i have had since last test ...Well today Fixing my mistake this should work now ...start and end of scan match now that should help ,next step is another slanted slit drum replacing the straight lines of this drum if not !

I did a bit of a photo construction of the small drum rebuild ..and you always change things with a better idea you have learnt.

If any thing its a lot neater now to,i am more happy with the way i did the line slits the old way it was hand adjusted this is now just done with a stanley knife which gives a nice thin line.

Its also a full 12 lines now which i suppose means my stepper can run slower.

Now on to replacing the luxeon driver transistor and another test and as always fingers crossed :roll:
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All done and back for testing ; )
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Postby Metallica Man X » Mon Feb 20, 2012 6:14 pm

Very nice

What are those 9 little things attached to that board in picture 366? ...I don't think I've ever seen anything like them before...
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Postby Harry Dalek » Mon Feb 20, 2012 11:56 pm

Metallica Man X wrote:Very nice

What are those 9 little things attached to that board in picture 366? ...I don't think I've ever seen anything like them before...


Thats the light 9 Luxeon LEDS all one watt so 9 watts in total.

Thinner the drum slits more light you need and its going passed 2,,,, twice the light loss i expect .

I will play around with it again midweek when i have a bit more time .

Thanks for the interest

:wink:
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Postby Harry Dalek » Thu Feb 23, 2012 5:05 pm

Well my Diffuser rebuild on the out side of the drum was a dud ! i was getting double lines which i didn't when it was before the line slit mask so rebuilt it again So sorry about that post it was a mistake for sure !:oops:

I am getting my first images after my rebuild rebuild now, bit crappy for a start but there they are first go's today .

So Its crude but a proof of concept at least .

Since i was trying the NBTV standard onit and the NBTV test card its on its side as this things more a Telehor i suppose .

You will notice you can adjust the image size again when you adjust the small drum speed ....with the letters ...

OH well getting there.
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Postby AncientBrit » Thu Feb 23, 2012 6:32 pm

Harry,

For the slits in the card do you make just a single cut and rely on the gap opening when you curve the card?

If so, how consistent is the slot width from top to bottom when assembled?

Keep up the good work, excellent instruction course as others have already said.

Kind regards,

Graham
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Postby Harry Dalek » Thu Feb 23, 2012 8:59 pm

AncientBrit wrote:Harry,

For the slits in the card do you make just a single cut and rely on the gap opening when you curve the card?

If so, how consistent is the slot width from top to bottom when assembled?

Keep up the good work, excellent instruction course as others have already said.

Kind regards,

Graham


Hi Graham

Yes its sort of like that for the slanted slits after you make the cut even flat the cut is fine enough for the light but it does spread a little as you are thinking as its wrapped inside the dvd drum lid ...
As you saw in the passed post i made one like that for the little drum but i have not used it for this test because of light loss having 2 very fine slits ...so i went back on my word and did it the old way for 2 reasons ...

First most if not all plastic drums have are tapered ,the small drum is 2 or 3mm from one end to the other so..if i use the paper slits partly cut into the paper and wrap it inside or out side of the drum theres a gap at one end ...not so bad or important for the large drum but i need space with a diffuser, thats the second reason i need it close as to the drum for room between it and the luxeons .

I cut out my paper 2.4cm wide 8cm high pasted these to the inside of the small drum as it tapers up theres a slight v to the line after all the paper slits are made i use another smaller thiner cut out rectangle of paper paste these from where the small bottom line starts and keep it that width and that fixes the tapering problem ....i sort of kept this drum slit width 2 or 3 times the size of the large drums for no other reason but for increase light level ,i think i could make it thiner for testing later on from doing the same from the out side of the drum ....just to see its limits .
The good thing about having the paper glued to the drum tight i can now do the same for the diffuser via a hot glue gun ..and that worked
i can just still see the 9 leds when bright so i might try another layer of that plastic .

Thanks Graham i know its all nice to make something and show it working with a nice picture but i think it helps no one else really you have to see it evolve..mistakes and all ,i'm ok with a red face from time to time if it helps ,i know i fail too but trying is the point of all this.
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 » Thu Feb 23, 2012 10:50 pm

Thanks Harry,

Graham
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