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Tag Archives: control

Heres a home CNC/drawing project with a twist. The drawing machine uses the time it takes for ink to bleed in to blotting paper to create a grayscale image. More information can be found  here along with some other awesome projects like a street art quadracopter and gesture driven drawing machine.

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I learnt so much in the home brew CNC workshop and I am very aware that if I don’t do something with my new found knowledge soon then I will forget most of it. I am a collector of broken junk and in my collection I have an A3 scanner and an A4 scanner. I have decided to turn these deserted and tired old pieces of equipment into a homebrew plotter / engraver (if all goes well.) The first step was to take the Grbl ready Arduino from a previous post and make it control a stepper motor. I have been leant 3 stepper motor drivers to experiment with, the documentation for the drivers can be found here. The A4983 stepper motor driver is a very compact driver perfect for smaller CNC projects. The documentation for the A4983 is very good so it was very easy to connect it up to the Arduino and the stepper motor. The pictures below evidence my setup with the driver running full steps. I have not experimented with micro steps yet but the results are very promising.

The wiring:

mac to arduino - arduino to a stepper motor

Being quite new to hacking components i am completely curious about how the small things work. I have been on the hunt for a servo stepper motor for a while now just to experiment with and control using the Arduino. I was told that printers quite often have stepper motors in them so i blagged a printer and started yanking it apart in a rather brutal fashion. With components and plastic discarded everywhere i recoiled in disappointment. After reducing the poor defenseless printer into smithereens all i had to show for it was dc motors 😦 How then did the printer control the movement of the laser-jet so accurately?

Make magazine came to the rescue as always. Recently on there blog they posted a link to this blog :

A BIG MAGNET PICTURES FROM AN ACCUMULATOR.

A big magnet has a post explaining “Using a DC motor as a servo with PID control” which is what i have encountered when hacking my printer. This technology is not just in printers its everywhere. Its in your printer, Computer mouse, scanners and so much more. A DC motors and an optical encoder are used to replace expensive stepper motors. PID stands for proportional–integral–derivative.

Wikipedia says:

PID is is a generic control loop feedback mechanism (controller) widely used in industrial control systems. A PID controller attempts to correct the error between a measured process variable and a desired setpoint by calculating and then outputting a corrective action that can adjust the process accordingly.

If you are wanting to control movement from a motor and don’t want to spend on expensive stepper motors you should really consider reading this blog.

A big magnet

thank you Big magnet

thank you Make magazine

Recently i have been pondering over how the hell CNC milling machines get such precision based vector lines. I was hoping to find some tutorials for arduino that would explain the theory behind this technology. All i found out so far is that the whole thing is fairly confusing. Despite my confusion i am very happy to have found this CNC controlled etch a sketch. Its not a toy its a precision engineers dream.

A couple of people have acheived etch a scetch prefection:

http://axis.unpy.net/etchcnc

http://instruct1.cit.cornell.edu/courses/ee476/FinalProjects/s2004/jml66/EAS_final.htm

and last but not least (check out the retro main image):

http://neil.fraser.name/hardware/etch/

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