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USB Turntable

What do you think is the best way to control a turntable?

USB
15
88%
Microcontroller
2
12%
Other
0
No votes
 
Total votes : 17

Re: USB Turntable

Postby Bongobat » Thu Jul 30, 2009 3:23 am

Hi again,

Well I guess I am just too impatient :oops: I just got an email informing me the bug in WcCtrl is fixed: http://www.burri-web.org/bm98/soft/wcctrl/index.htm
This should make things a lot easier but I now need to rewrite a few things.

Using my wcctrl copy hack I did a quick automation test on a bottle of correction fluid. This was a completly automated scans with texture shots. :wink: This was scanned with the room lights on. The software will switch on an LED light but I havent made it yet.

Greg
Attachments
45.jpg
45 degree scans arranged in David
meshlab.jpg
Fused result rendered in meshlab
meshlab.jpg (29.35 KiB) Viewed 5549 times
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Re: USB Turntable

Postby Khalid Khattak » Thu Nov 05, 2009 6:29 am

Greg, thanks for sharing the bright ideas and implementation in a ingenious way.. One question to ask you, Your circuit shows controlling of One stepper Motor and I think you are using to turn the TURNTABLE only.. How can we add another stepper motor to control the Laser?... Also can you please show us How you will light the LIGHT to take the Texture Snapshot...
Can you please share your latest software work with us? Also kindly can you snap some pictures of your Hardware setup?.. You are using amega8 how you interfaced it... some more details please..

Best Regards
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
CAMERA:
David CCD Mono USB
LASER:
David 5mW Green line laser
PROJECTOR:
3D LED Mini Projector 250lumens, Native 1024x600
[b]http://free3dscans.blogspot.com/
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Re: USB Turntable

Postby Khalid Khattak » Fri Nov 27, 2009 12:33 pm

Greg what programming software you are using to make the GUI ?... I like it..Can we make a GUI in visual BAsic?
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
CAMERA:
David CCD Mono USB
LASER:
David 5mW Green line laser
PROJECTOR:
3D LED Mini Projector 250lumens, Native 1024x600
[b]http://free3dscans.blogspot.com/
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Re: USB Turntable

Postby Bongobat » Sat Nov 28, 2009 6:47 pm

Hi Khalid,

I used Visual Studio C++ 2008 Express. You can download it for free here: http://www.microsoft.com/express/default.aspx

Im now planning on redesigning things a bit. I have tested simply plugging the turntable circuits into two arduino digital outputs and I made a test sketch that runs the sequence and It seems to work fine. In this way it becomes a universal turntable for computer or microcontroller. :wink: I need to add this to my old sketch though when I find time.

Greg
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Re: USB Turntable

Postby Khalid Khattak » Sun Nov 29, 2009 1:23 pm

Thanks Greg for insight.. I started planning to pseudocode Visual Basic using Mscomm32.ocx... I wonder How com0com work?... Can you help me in showing the visual C source code if possible..or if you can email me
engr_khalid_khattak(@)yahoo.com

I have some questions in mind...

1- Can we pass the 'Variable value' into arduino function from the GUI?.. Like i want to send the 'motor steps' value from a textbox to arduino hard coded sketch...( this will ease many here..some using 48, some using 200 and many using gearboxes with stepper)

2- How the David and Arduino communicate at the same time..i think you are using com0com.. and if i have Laser, Light and David..then i have to use three ports??? How will i arrange them in Com0Com?... I will study the com0com stuff later today...

Thanks and Best Regards
PC: Dell Inspiron i3, 2.27GHz,4GB RAM,64 bit windows 7
CAMERA:
David CCD Mono USB
LASER:
David 5mW Green line laser
PROJECTOR:
3D LED Mini Projector 250lumens, Native 1024x600
[b]http://free3dscans.blogspot.com/
Khalid Khattak
 
Posts: 942
Joined: Thu Apr 23, 2009 1:30 pm
Location: Pakistan

Re: USB Turntable

Postby Bongobat » Tue Dec 01, 2009 2:15 am

Hi Khalid,

Im just a little reluctant to post this stuff because it is not the conventional way of doing things and it is experimental and may be a bit confusing. However here is the release version of what I am currently using. I need to find the time and get everything in order but I dont know when that will be sorry. Basically this just sends out an "S" to start the easydriver and a "T" to stop and rewind it. The arduino sketch is responsible for the counting and the rewind. The turntable buttons just run a turntable made like the one on this page. The light/ laser buttons are experimental and have not been tested. A lot of stuff that I wanted in it are still not in it like pulse sync and being able to send the arduino a variable speed value although Gunter found a way that looked promising. The automation works well enough for me. Here it is to play with until I can refine this rough sketch. :oops:

P.S I have uploaded the source code of the simple turntable software to the first post. That may get you started.

Greg
Attachments
Slingshot2.zip
Slingshot2 laser/turntable automation software (bridge application)
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Re: USB Turntable

Postby Bongobat » Mon Mar 01, 2010 7:26 am

Hi,

Someone may have already had this idea so sorry if this is old news but I came across a nice cheap turntable bearing that should be widely available. It is called a lazy susan mechanism: http://www.lowes.com/pd_71060-255-46506 ... logDisplay When I get a chance I am going to pick one up and direct drive it with a small stepper and see how much weight I can move. In the meantime does anybody know how to calculate this mathmatically? How big of a stepper motor would I need to direct drive something like 50 lbs?

Greg
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Re: USB Turntable

Postby Marko » Wed Mar 10, 2010 10:51 pm

hey, that mechanism is used to turn TV's on a table if im right? those things are usually assembled by small cylinders on which both halves rotate, not really a good bearing, since they are made from soft metal and they deform under load. required power to rotate something that weights 50 pounds depends on the moment of inertia of that item and losses in the mechanism, since the scanning action is fairly slow process, that inertia isn't much of a problem ,

it would be a problem if you needed to spin a 50 pound item from a standstill to 1000 rpm in one second. speed is not an issue in a turntable.

so its up to losses in the mechanism , in normal rolling element bearings losses are around 1% per bearing pair(or axle) . the problem with those lazy susan mechanism's is how well are the bearing elements made, if its made from some stiff materials like 2 plates of glass with steel rollers in between the required power to turn that 50 pound item will be low, if they are from soft mild steel and you overload the mechanism, the rolling elements will digg themselves into the "bearing races" and the required power will be high.

why dont you get a industrial grade ball bearing and place a plate(white plywood, or something cheap) on it , that way you get a turntable that will have low mechanism losses. you can suspend the bearing on the inner race, and set the plate on the outer race, and connect the stepper via friction drive or a belt to the outer race.

as far as the calculations of the stepper motor ,as is said its all up to losses in the bearings, just calculate the friction on the radus of the bearing , that is equal to the required torque of the stepper motor times the angular velocity ( power = torque* angular velocity) and the required power turn the turtable with 50 pound item is force of friction that you already calculated times the speed of a point at the circumference of the bearing, that is the point on which the friction of the bearing acts ( power=force*velocity ) , this is at steady state rotation , to accelerate and decelerate more power is required, but since the mechanism is so slow as i said before that can be ignored. in that case it all depends on the max velocity you want to drive your turntable, that is you can drive it with the weakest stepper that you can find if you have the adequate reduction in drive. principle of the levers . you just need to chose the speed

since english is not my native language some technical terms could be wong, but i think i used them all right.
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Re: USB Turntable

Postby Bongobat » Wed Mar 10, 2010 11:36 pm

Hi Marko,

Marko wrote:hey, that mechanism is used to turn TV's on a table if im right? those things are usually assembled by small cylinders on which both halves rotate, not really a good bearing, since they are made from soft metal and they deform under load. required power to rotate something that weights 50 pounds depends on the moment of inertia of that item and losses in the mechanism, since the scanning action is fairly slow process, that inertia isn't much of a problem ,


Well it's a hardware part so it can be used for anything your imagination requires but technically this was intended for food service: http://en.wikipedia.org/wiki/Lazy_Susan Specs say it can rotate up to 500 lbs. Not sure I need to rotate that much. It has ball bearings sandwhiched between two plates. Quite sturdy and smooth. Because of the way it is made you can have very widely spread loads as opposed to a regular bearing which is balanced best if the weight is evenly distributed over the axis. You can also get them in even bigger diameters than this one. I think its the same bearing principle that is used on turntables able to move cars and trains :wink:

I have already tried a direct drive with a small stepper and it was not sufficient as suspected. Yes with gearing it will work but I was trying to eliminate that. Thanks for the info on the math though.

Edit: Walter had posted a similar bearing device that comes ready for a drive sytem: viewtopic.php?f=2&t=857&p=6023#p6023 It looks like a slewing bearing: http://en.wikipedia.org/wiki/Slewing_bearing but I could not easily find such an affordable thing in the U.S

Greg
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LazySusanProfile2.jpg
Lazy Susan Mechanism
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Re: USB Turntable

Postby Marko » Fri Mar 12, 2010 11:38 am

a good bearing will set you back 50$ so the lazy susan will probably be a cheaper and simpler solution because it already has mounting points ,

i thought it has like 6 or 8 rolling elements across the 360 degrees , but these have rolling elements all around, thats good .
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Re: USB Turntable

Postby sascha » Tue May 04, 2010 8:53 pm

Hi,

First of all, I have to say that DAVID had impressed me several months ago when I had decided and bought starter kit.
Looking for the best way for scanning without background, I decided to try the way that Greg explained in his post "USB turntable" with two wire circuit for controling unipolar stepper motor.
I have successfully installed rs232 and two virtual serial ports.
Unfortunately, something is wrong with my solderless protoboard circuit, because my stepper only vibrates, and there is no chance to move it regardless the order of the stepper wires I had connected to uln2003.
Could someone explain to me all detail settings (for DAVID, circuit and used serial ports) about this way for controling stepper (using Greg's softwares like turntable and automatedstep).
For easier understanding here are some pictures of what I have done.

Please note that electronics is not my basic occupation.

In advance, thanks to all.

Sascha
Attachments
scheme.pdf
(58.95 KiB) Downloaded 255 times
circuit.pdf
(160.72 KiB) Downloaded 244 times
inside of stepper motor.pdf
(186.17 KiB) Downloaded 225 times
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Re: USB Turntable

Postby Bongobat » Wed May 05, 2010 11:41 pm

Hi Sascha,

The turntable I presented here was not intended to move a laser for scanning. It is designed for moving a turntable that moves the object into different positions for scanning to easily achieve a full 360 degree model.

I do not recomend it for scanning because it has very coarse full steps and I could not figure out a way to quickly rewind it. However it should rotate a laser if you want to experiment. You show two AA batteries in your circuit but they are labeled 12V? 2 AAs wil only give 3V and I do not think this wil be enough for a stepper. I use a 12 V AC/DC power supply with a regulator circuit giving 5V to the electronics but the unregulated 12 V goes to the motors. For the software I think you should start by getting it to work with this simple program: download/file.php?id=2040 from my first post: viewtopic.php?p=7972#p7972 You can also download the Visual C++ there too if you want to try to make your own program or see how the sequence works.

Greg
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