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Slingshot Basic

Slingshot Basic

Postby Bongobat » Tue Aug 17, 2010 5:00 am

Hello All,

I realized after all this time I have never uploaded a picture of my planeless laser scanning rig. So here is some pictures of the robust basic version. I have also attached the Windows Slingshot Basic software for free if anyone wants to use it with their system.

Slingshot Basic features include:
USB interface
Capable of powering the high current draw green lasers
1.8 degree stepper motor, 70: 1 worm gear and 1/16 microstepping driver = 224000 steps per revolution or a step angle of 0.0016
Simple clamp type hardware positioning for easy scalability (attaches to standard water pipe for constructing various setups)
Fully controllable and configurable through the Slingshot Basic software.
Capable of planeless scanning

Greg
Attachments
Slingshot Basic.jpg
Slingshot Basic Hardware Setup
Slingshot Basic Software.jpg
Slingshot Software
Slingshot Basic Software.jpg (52.6 KiB) Viewed 5281 times
Slingshot Basic.zip
Slingshot Basic Software for Windows
(162.16 KiB) Downloaded 217 times
DealExtreme red line laser, Microsoft Lifecam HD-5000
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Re: Slingshot Basic

Postby GeoffT » Tue Aug 17, 2010 10:36 am

Hi Bongobat,

That looks very neat and robust, have you described your hardware set up on the forum? I'm only just starting out, I'm very impressed with the starter kit but I would like to go planeless in the near future. Obviously there are many different set ups that people have built but it's often difficult to find the information necessary to build something like that without referring to numerous different threads.

Thanks,

Geoff
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Postby hal » Tue Aug 17, 2010 2:45 pm

Great work, Greg.
Really nice solution :shock:

Mattia
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Re: Slingshot Basic

Postby pottersfriend » Tue Aug 17, 2010 3:31 pm

Nice setup Greg. I like the look of the Slingshot software, much more refined. Does it or will it have turntable controls?

Another question I have is what vehicle you got your wiper motor/gear box from and how hard was it to adapt for use with your stepper motor. I would like to do the same but have tried a 1990's era Toyota Corolla and it seems a bit flaky.

Anyway, your setup looks great.
Darin
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Re: Slingshot Basic

Postby dickda1 » Tue Aug 17, 2010 4:42 pm

Very nice setup.

There are a number of us Greg that would like more information about the mechanics. It is hard to gage the size of the stepper motor, but it looks like a Nema 17. Is that right? I have a Nema 23 on my setup, but it has a large current draw on the driver board. Are you using an Easydriver or an Arduino MotorShield? Could you tell us more about the gear box as Darin mentions? Are you using an elastic band or some other passive braking to remove backlash?

Sorry for all the questions, you and WalterMo have some really nice designs.

Dick
Last edited by dickda1 on Fri Sep 10, 2010 6:05 pm, edited 1 time in total.
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Re: Slingshot Basic

Postby Bongobat » Wed Aug 18, 2010 9:07 am

Hi,

I use the Pololu A4983 motor driver carrier:
http://www.pololu.com/catalog/product/1201

Here is the link to the stepper motor:
http://www.jameco.com/webapp/wcs/stores ... llDownView

The gear is a Dorman window lift motor part 742-143. It is used in several GM models and you can get it at autozone.
You have to modify it to get it to work:

You need to cut the worm from the original rotor assembly and attach it to the stepper shaft. I use a piece of aquarium tubing as a flexible coupler with nylon zip ties to hold it tight. You also need to make a plate to mount the motor to and then mount the plate to the gear body. You must be very precise when making the plate because any eccentricity or imperfectness will cause the motor to subtle slow at certain points and cause problems with a planeless scan. When done right it works great though.

Dissasemble the gear completely and wash the grease off of everything.

The gear has an internal bushing and you should stiffen that up by adding small washers around the sides and cutting the small tabs on the top and bottom of it. You aslo need to remove the rubber grommet on the cover plate because it causes too much resistance and if not modified will cause problems with planeless scans. Once you modify the gear you should be able to spin it freely with the worm gear removed.

I have implemented a spring instead of a rubberband for the backlash. I noticed my rubberbands were deteriorating fast. So I made a very strechy spring by winding a guitar's G string around a nail with a drill. This spring's elastisity was perfect but you should be able to find similar ones at a hardware store.

I also took Walter's suggestion allowing the motor to rewind a few steps beyond the start point and then forward to the start to mesh the gears correctly.

EDIT: Also add a small bit of tape between the outer cog gear's square end where it fits into the worm gear before sliding it back into the gear and this will eliminate any play.

EDIT2: Sorry , I have no plans to implement a turntable in the basic software at this time.

Greg
Attachments
motor shaft mod.jpg
Worm Modification
window lift gear mod.jpg
Worm Wheel Modification
cog gear.jpg
Eliminating remaining play
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Re: Slingshot Basic

Postby pottersfriend » Thu Aug 19, 2010 6:40 pm

Greg,

Thanks for the additional, and detailed, information. Much appreciated.

I was also curious what camera and lens you are using. I have recently purchased a camera and need to get a lens. Do you have a model number and specs of the lens you are using? I have been having trouble finding a 1/2" 6mm lens with manual focus/iris (with locking rings) here in the US. If you know of a source I would appreciate it.

Thanks, and again great looking scanner setup.
Darin
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Re: Slingshot Basic

Postby dickda1 » Thu Aug 19, 2010 9:13 pm

Greg,
The level of detail here is really great. Sometimes, you and Walter and others must put this stuff out on the forums and think that no one is looking. There are a bunch of us that are looking at magnified pictures in detail and reading code and getting ready for our own attempts. Thank you!
-Dick
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Re: Slingshot Basic

Postby hunkatibor2 » Mon Aug 23, 2010 3:21 pm

Intel Xeon E5410 2.33GHZ 16GB RAM Windows 7 64bit David 4.5.0
2 Basler A622F camera 2 Tamron Asfirical AF 28-80mm lense
LG DLP Projector PF1500G Canon D40 Tokina 17-70mm 1:2.8-4,5
Humanti Calibration panel system and Alignmed&Two camera
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Re: Slingshot Basic

Postby WalterMo » Mon Aug 23, 2010 7:35 pm

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Re: Slingshot Basic

Postby Bongobat » Tue Aug 24, 2010 2:36 pm

Hi Darin,

pottersfriend wrote:I was also curious what camera and lens you are using. I have recently purchased a camera and need to get a lens. Do you have a model number and specs of the lens you are using? I have been having trouble finding a 1/2" 6mm lens with manual focus/iris (with locking rings) here in the US. If you know of a source I would appreciate it.


The camera pictured is the Phillips SPC900NC modified with this lens: http://www.ixbay.com/en/3-5-8mm-cs-moun ... -iris.html

Greg
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Re: Slingshot Basic

Postby pottersfriend » Tue Aug 24, 2010 6:48 pm

Greg,

Thanks for the info/link. Very affordable lens. I've Googled quite a few places and haven't stumble across that site before.

Thanks again, that helps a lot.
Darin
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Re: Slingshot Basic

Postby bperez » Tue Feb 08, 2011 5:10 am

Greg,

Many thanks for the details provided. Please excuse my ignorance regarding the electronics involved; however, I was wondering if you could provide any additional detail regarding your electrical set up. Particularly, how the motor driver carrier is integrated into the assembly.

Best Regards,

Basil
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