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Author Topic: Project Sans Arduino
matt
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Posts: 2
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Post Project Sans Arduino
on: August 19, 2012, 04:17
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I am a bit of an arduino lover myself, however I have several serial/parallel connected stepper controllers. Having built two cnc machines I have a large investment in technology and controllers - is it possible to run a similar program through your serial connector right to the stepper controller?

Any thoughts?

I am a huge fan of your work Sandy, I am determined to build a machine for my self! Thank you for making it so approachable.

sandy
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sandy
Post Re: Project Sans Arduino
on: August 19, 2012, 19:20
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Hey Matt, you're very welcome! It probably depends how smart/dumb your controllers are. I suspect they are a lot smarter and faster at driving motors than an arduino, but might be less flexible in how they interface. I've never really looked at how those kinds of machines work - how much work goes on in the controller hardware, and how much is in the software. I _imagine_ they are driven by G-code, which is not so different to what polargraph speaks.

At it's core, my polargraph controller software expends a lot of energy converting cartesian coordinates into the native polar (or dual-triangulated) coordinates system. It communicates using the native system.

At it's core, the polargraph firmware (arduino and motor drivers) does little more than move motors to exactly where it's told to. In practice there's more on-board, but that's all just sugar. Essentially it's nothing more than an interface that converts ASCII commands to step commands.

So there's not actually that much to replicate if you wanted to do that. Changing the form of the commands that the controller software spits out would be fairly straightforward too. I never really could think of a good reason to convert polargraph to use g-code, but I suppose this is it. I guess the unknown apart is the hardware aspects - what data protocol the CNC machine uses to get its commands, and how a connection to the machine would be got through your OS.

sandy noble

matt
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Posts: 2
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Post Re: Project Sans Arduino
on: August 19, 2012, 21:41
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Well, the CNC world covers everything that you have covered. Let me draw a simple picture:

At the core you start with GCode which comes from either a drawing/model that is converted by a program or if you prefer, just punched out line by line in notepad. The computer then takes that code and uses a controller program like Mach3 which takes your GCode and the variables specific to your control system (steps, ballscrew pitch, belt reduction, intended maximum speed and acceleration) and outputs through a parallel/usb port a series of pulses - 5v high/low signals to your controllers. Each pulse group specifies a step command and direction. So in essence the hardware is not smart at all.

All of the brains are in the computer and the controllers take a step/direction signal and move the motor as needed.

If you have ever looked at the range of stepper controllers there is a VAST assortment of cheap and expensive solutions that are very flexible. I am curious if there might be a method of taking your model and modifying it for different setups.

It might just be smarter to take and Arduino and modify the command/direction pulses to interface with my stepper controllers - I am pretty sure it has been done a thousand time already.

My thought process is, if I could open up the usage of more mainstream stepper controller/motor combinations then you/I could use more powerful systems. (In a previous project I used Gecko 203v's to push 1200 Oz/in (8.474 Nm) steppers using 72V DC and 4-8 amps of current to achieve some incredible performance).

I am really just putting some ideas out there and trying to show parallels between what you have made and typical computer based homemade CNC Systems. I am going to build one of these, but having experienced an extremely slow cnc machine, and spending the money to build a second quicker system I know what it is like to go from an 8 hour run time per part (in this case drawing) to a 2 hour run time (with the quicker machine). Tuning the inertia/acceleration/drag characteristics would be an entirely different situation as well.....

I will research what kind of commands the arduino sends to the shield and see if there is some similarities between that and high/low stepper controllers....then maybe I can build some kind of hybrid system. Perhaps I can put a program together computer side and take some of the conversion processing off of the arduino?

Thanks for taking the time to chat...so many possibilities - my kids are just getting to the age of robots and I want to start getting more hands on... and I also feel it is about time I give something back to the community as well.

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