New Drum monitor build

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New Drum monitor build

Postby Harry Dalek » Sat Jan 21, 2012 7:35 pm

Using what i have learnt from the last one i am having a go at a new monitor,its still at the early stages working things out ,the drum is going to be the 50 dvd drum holder .
i am toying with the idea of using 2 trying to do it a little differently so i will see how that gos ,have been playing with the optics side of it to see if the new idea would work and seems ok.

Started with the simple L shaped case idea many a home made CRO must have started as so that makes it easier .

I scrapped the viewfinder bit from a old photo enlarger ,it fits some glass between .

I would love to use 2 stepper motors this time as well but i don't think i can get the speed with direct coupling for the nbtv vertical so i will have to think about it and check my other stepper motors perhaps gearing ,this large PC fan has me interested but if all thats not up to the job just go for a normal DC.
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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 Metallica Man X » Sun Jan 22, 2012 2:10 pm

Interesting.

I wonder how well that lid will be able to handle the RPMs....
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Postby Harry Dalek » Sun Jan 22, 2012 6:41 pm

Metallica Man X wrote:Interesting.

I wonder how well that lid will be able to handle the RPMs....


Hi MM10

I don't think i will have a problem with the speed on the drum lid as my last one was about the same but bigger cut in half and the last thing it did was hold Lettuce Leafs...it would of been doing over 1500rpm i also had no problems at full speed of the motor what ever that was 2000 or so rpm .

Its more how well you connect the drum to the direct drive motor ,it was easy on the last one as it was from a 80s video disc player had a large flat plate and screw on connections .

I hope to use a stepper motor on this but they tend to be to slow for the use and clog at higher speeds but i will see if i can increase the speed with gearing or pulleys.....see whats in my junk box !
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 Harry Dalek » Sun Jan 22, 2012 10:37 pm

I have been working out a way of speeding up my stepper motor what you see in the pictures 1 turn of the large drive turns the small 3 times so i will see how that gos .

Between the HD platters i have a thick platter of steel its a bit like a fly wheel might help stop clogging it will be interesting to see ...
my other stepper motor sort of uses a small one which i think was used to do the same thing .

I just picked a stepper motor out of my ebay win collection see how this one go's another unipolar.
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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 gary » Mon Jan 23, 2012 2:07 pm

What speed do you need Harry?, I have successfully driven a Nipkow disk with a stepper at 750 RPM and I wouldn't think doubling that would be a problem. Somewhere on this forum I have an overview of how it is done (I think). You need a decent (not tin-can type) stepper and constant current RL driver. I found that I had to ramp up the speed to overcome resonances etc - no big deal.
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Postby Harry Dalek » Mon Jan 23, 2012 4:16 pm

gary wrote:What speed do you need Harry?, I have successfully driven a Nipkow disk with a stepper at 750 RPM and I wouldn't think doubling that would be a problem. Somewhere on this forum I have an overview of how it is done (I think). You need a decent (not tin-can type) stepper and constant current RL driver. I found that I had to ramp up the speed to overcome resonances etc - no big deal.


Hi Gary

:)

Thats good to know ! i wasn't sure anyone had tried it for those speeds ..i think i do or want it for double speed 1500 rpm or so i am just seeing what i can do before i work out the number of lines on the drum .

I will have to try and find your stepper messages ...when i was working out the last one i worked on i read bipolar ones 4 wire ones are the newer type and do run at faster speeds ,i have been more lucky with unipolar bit of a rut i am in .

The ones i have tested all run at different speeds before clogging seemed to me to be a bit of pot luck ...i am not sure what you mean about other than tin can types ,the ones that i think of like that are small flat printer types ?.

I am trying for 32 line again but 60 line would be nice but again depends on what happens when i test my motor .
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 Harry Dalek » Tue Jan 24, 2012 8:28 pm

Yesterday i attached the drum to motor ,had to adjust the drum a little cutting off the bottom lip to the dvd drum and middle theres was a round plastic protrusion that i cut off to...needed the drum flat on the top HD platter to stop wobble ...

Now all workable with also removing the metal rings that separate the Hd platters i should get a little more speed.

Have to do some speed tests now .
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Postby gary » Tue Jan 24, 2012 9:04 pm

harry dalek wrote:i am not sure what you mean about other than tin can types ,the ones that i think of like that are small flat printer types ?.


Well, they are commonly found in (modern) printers, yes. The "tin-can" types are those with thin walled, pressed metal enclosures. The stepper you show in the images is a nema type of lowish torque, commonly found in floppy disk drives I think, it may work but the chances of success would be greater with a stepper of, say, 35-50 oz-in torque.
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Postby Harry Dalek » Tue Jan 24, 2012 10:16 pm

gary wrote:
harry dalek wrote:i am not sure what you mean about other than tin can types ,the ones that i think of like that are small flat printer types ?.


Well, they are commonly found in (modern) printers, yes. The "tin-can" types are those with thin walled, pressed metal enclosures. The stepper you show in the images is a nema type of lowish torque, commonly found in floppy disk drives I think, it may work but the chances of success would be greater with a stepper of, say, 35-50 oz-in torque.


Hi Gary

Learn something every day as they say !
I got about 10 off ebay 1 dollar a stepper so i have a few spare to try a few will still fit the gearing if this one fails...i will see when i test.
I gather from what you say bigger the size of stepper the better ? This ones a 6 wire type i think they can be wired to work with either biploar or unipolar drivers....
Without the HD platter holder rings i am now getting nearly 4 and a half turns to one turn of the stepper ,it doesn't take much to turn it so i am hopeful ,i don't think it will take much torque but seeing it working is what i need to do next.
Thanks for the info there gary always appreciated.
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 Harry Dalek » Tue Jan 24, 2012 10:17 pm

gary wrote:
harry dalek wrote:i am not sure what you mean about other than tin can types ,the ones that i think of like that are small flat printer types ?.


Well, they are commonly found in (modern) printers, yes. The "tin-can" types are those with thin walled, pressed metal enclosures. The stepper you show in the images is a nema type of lowish torque, commonly found in floppy disk drives I think, it may work but the chances of success would be greater with a stepper of, say, 35-50 oz-in torque.


Hi Gary

Learn something every day as they say !
I got about 10 off ebay 1 dollar a stepper so i have a few spare to try a few will still fit the gearing if this one fails...i will see when i test.
I gather from what you say bigger the size of stepper the better ? This ones a 6 wire type i think they can be wired to work with either biploar or unipolar drivers....
Without the HD platter holder rings i am now getting nearly 4 and a half turns to one turn of the stepper ,it doesn't take much to turn it so i am hopeful ,i don't think it will take much torque but seeing it working is what i need to do next.
Thanks for the info there gary always appreciated.

Since writing this i have tested the motor it sure works but what a noise !at top speed YAKES no wonder the geared mechanical tvs of the early 30's never caught on ...Apart from that :shock: it sure works i think by the top speed i think i could do 1500rpm ...i will have to look into if the noise problem can be fixed but i am sort of thinking the drum is amplifying the sound which is not good ! playing around with it a bit more it really has to do with the speed over a point its rattles ,the caps on the clock 555 astable that i change for speed cause this at different speeds so i have to look into this on my scope perhaps its the pulse width...mmm
Oh well least it go's
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Postby Harry Dalek » Thu Jan 26, 2012 11:28 pm

Big redesign of the pully system today i could not stand the gearing noise !

So i have given it another go this time i am direct driving the stepper motor to the HD this seems to work better also changed the belt for a thiner one ,i have tested 2 other steppers and the other in the photo connected to my stepper board i will might replace the one attached seems to run a touch faster.

The new adjustments have slowed it down a bit i think from the geared version but rather the peace !

Should at least do 750rpm so i will keep that in mind .

Gary if you read this i have been reading your stepper motor posts and found them very helpful very much so on the bipolar side of things ...found your experiments using sine wave via pc to stereo amp pretty interesting ,the link to the home made turntable was pretty interesting too.

Sort of given me hope reading the posts seeing the same sort of ideas i am trying with the stepper ...

Yes these ones look like they are from a 5inch floppy drive ,i do still have a stepper from my 2000 teletype machine its pretty big hadn't thought of using that i might rip it out and test it since i know who to get it going now.

One thing i read about increasing speed voltage must go up well my drive seems to die if i use 12v to uln 2003 driver , pretty warn at 5v so i must of pushed it ,should work at 12v but the steppers must killing it with back emf.
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Postby gary » Fri Jan 27, 2012 9:44 am

As a rule of thumb, if you are using the LR form of controller, you need about 10 times the steppers rated voltage. A lot of these steppers are rated at 2 volts or less (BTW when I say rated it has nothing to do with the breakdown voltage it is the voltage needed to bring the current up to the rated value), so a supply of around 20 volts is best but I am pretty sure I got up to 750 RPM on less than that.

BUT! above all remember that the rated current must not be exceeded (at least for any length of time) and so a series limiting resistor is mandatory - this form of controller is the least efficient (in terms of energy) of all the stepper controller methods, but it is also the easiest and cheapest by a country mile.

It is normal for a stepper to run warm, in fact very warm - the good ones are built to handle that.

Note also that with a bigger stepper the current will go up to a level where the ULN2003's are no longer viable (from memory they are about 1 amp - whereas the stepper I used required 2.5 amps). But don't forget when running in bipolar mode you just need 2 sine wave inputs (90 degrees out of phase).

To power it I used (to compare) a number of methods:

A power amplifier (very good but expensive, also reaching the required voltage can be a problem in some circumstances).

A push pull power transistor amplifier (good but was tricky to get going)

A class A amplifier pair using LM317s believe it or not (I never quite got this going at least to my satisfaction but is a plausible solution but requires hefty output capacitors).

I had intended to experiment until I had a cheap but effective controller that included ramping (essential) but got distracted and I will be more-or-less out of electronics design until I build my new shed which is a few months down the track I fear.

If someone else wants to pick the ball up on that all that is required is two power sine wave generators (and they can be pretty rough sine waves) with a common variable frequency - I was using a PC to generate the sine waves but it should be fairly trivial to use a cheap PIC or other micro controller. I think a simple push-pull amplifier will be the best solution but others may have further ideas - my main criterion was it to be cheap and simple.

PWM rather than LR may also be explored.
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Postby Harry Dalek » Fri Jan 27, 2012 12:29 pm

gary wrote:As a rule of thumb, if you are using the LR form of controller, you need about 10 times the steppers rated voltage. A lot of these steppers are rated at 2 volts or less (BTW when I say rated it has nothing to do with the breakdown voltage it is the voltage needed to bring the current up to the rated value), so a supply of around 20 volts is best but I am pretty sure I got up to 750 RPM on less than that.

BUT! above all remember that the rated current must not be exceeded (at least for any length of time) and so a series limiting resistor is mandatory - this form of controller is the least efficient (in terms of energy) of all the stepper controller methods, but it is also the easiest and cheapest by a country mile.

It is normal for a stepper to run warm, in fact very warm - the good ones are built to handle that.

Note also that with a bigger stepper the current will go up to a level where the ULN2003's are no longer viable (from memory they are about 1 amp - whereas the stepper I used required 2.5 amps). But don't forget when running in bipolar mode you just need 2 sine wave inputs (90 degrees out of phase).

To power it I used (to compare) a number of methods:

A power amplifier (very good but expensive, also reaching the required voltage can be a problem in some circumstances).

A push pull power transistor amplifier (good but was tricky to get going)

A class A amplifier pair using LM317s believe it or not (I never quite got this going at least to my satisfaction but is a plausible solution but requires hefty output capacitors).

I had intended to experiment until I had a cheap but effective controller that included ramping (essential) but got distracted and I will be more-or-less out of electronics design until I build my new shed which is a few months down the track I fear.

If someone else wants to pick the ball up on that all that is required is two power sine wave generators (and they can be pretty rough sine waves) with a common variable frequency - I was using a PC to generate the sine waves but it should be fairly trivial to use a cheap PIC or other micro controller. I think a simple push-pull amplifier will be the best solution but others may have further ideas - my main criterion was it to be cheap and simple.

PWM rather than LR may also be explored.


Hi gary thanks for the very informative reply ...thats very helpful putting me on to the bipolar ideas i find very interesting and i want to try out some ideas here.

I had not noticed the stepper getting hot yet gary as i am just running the circuit + diver ic and stepper off the same 5v power supply.

I have noticed the 2003 driver ic getting very warm but driving this on a higher voltage i have killed 2 other 2003's so i have been keeping it at 5 volts /// i do have a better driver ic but i had more of these to test with ..

I was using a H bridge for the L293 for bipolar idea but i think i should of just used a jk flip flop to feed it from the sounds of it ...

I had not thought of using sine waves for steppers i wonder if it matters so much at higher speeds if its a square wave or sine wave but i am sure you are right that they run smoother on a sine wave....i am going to look into this .


Yes cheap and simple is the way to go gary its no point if the thing costs to much it defeats the purpose ....i like trying what i handy .


I just got my large 6 wire 70's stepper out for testing a Sagem 20pp50 51 04 what ever they mean...i think its a stepper due to the wires but i can not feel the steps or they are very fine.......


Good luck with the shed yes takes a lot of time up the building projects i will play around with your stepper ideas for sure .
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 » Fri Jan 27, 2012 6:41 pm

Keep up the good work Harry.

I always look to reading the results of your latest kit.

How do you find the time??

Cheers,

Graham
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Postby gary » Fri Jan 27, 2012 6:42 pm

My apologies Harry I thought you meant the stepper was getting warm.

But careful with your terminologies Harry - it is not the higher voltage that is killing (or warming) your 2003s - it can handle up to 50V - it's the commensurate rise in current (V/R) due to the higher voltage - by all means use a higher voltage but include a limiting resistor in each of the stepper windings to limit the current below .5 amp (or 1 amp if you have two outputs paralleled).

If you use square waves the risk of cogging will be greater than when using sine waves - it may not be significant at the higher speeds but I suspect it may well be.
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