Mechanics and Construction > Mechanics and Construction

Rotor Arm, My current project

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I started this about two weeks ago. Just finished the first arm section today and tested it lifting @3lbs attached at the end of the 8.5" section. I tried 5lbs and it would hold it in place but could not pull it up. Was really hoping for a 5lb lift. I had the stepper speed set in arduino for 100. It is a Shinano Kenshi 8V 1.2A 1.8 step angle which I pulled from a trashed copy machine.
The base is an old brake rotor with a roller blade wheel set in the middle being used as the rotation bearing.
The arm is rotated with a cog belt running to a stepper which came from an old heavy duty dot matrix printer. I wasn't  sure of the V so I started it out at 5V and its running great.

The altoids joystick came from my first arm and was really easy just plugging it in to Arduino's analog pins for first run testing.

My little stepper driver circuit uses the 2 I/O pin from Arduino to the ULN2003. I then move that signal on to higher power transistors that are capable of driving these steppers.

The third stepper located on the backside of the turret will drive the second stage (elbow) by cog belts with the first motor to pulley being on the pivot shaft of the first joint and then transferring that up into the arm. Will be staring on that tomorrow.

I know eventually I will have to decide on a better micro-controller than the Uno if I want the arm to do all I want it to but I haven't decided on which one to go with though. Any suggestions and comments are appreciated.

I forgot to add that all the aluminum was bought at a surplus store. I got 8 (10" x 5.5" x 1/8" ) plates for about $9.
All in, I will only have spent $60 to build this arm and that's including the Arduino. So after replacing the arduino with a BeagleBone or Axon I will probably go over $100. But that is still far less comparatively than what I see being spent on arms that can only lift a few hundred grams!  ;D

Might I ask, how did you shape your arm the way you did? 

Great project...well thought out.


--- Quote from: Bciaren on February 23, 2013, 10:40:18 AM ---Might I ask, how did you shape your arm the way you did?

--- End quote ---
All of the aluminum was cut using a jigsaw with just a wood cutting blade, and a hacksaw. I have tried the metal cutting blades in the jigsaw but they just don't seem to work well.

I'm bad about not designing things out first because I use mostly scrap and surplus parts so its usually touch and go just to see what is going to work right.

The first section of the arm, shoulder to elbow, I sized the gear at the shoulder end, and pulley at the elbow end then used one of those circle guides you can find at art stores to trace out circles about the size of the gear and pulley and spaced at the distance my cog belt would need to run. You can still see the patterns traced on the aluminum in some of the pictures.

Ive been a bit lazy the last few days but I almost have the elbow joint and cog belt arrangement done and hope to  pictures up tonight or tomorrow.


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