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I'm part of an open source hardware project called RepRap (open source 3d printer), and we're essentially developing a system that relies on a microprocessor to do things.  we're having to solve alot of the problems you've already solved, and it seems sort of silly to re-invent the wheel.  i was thinking that instead of building boards from scratch, we could create shield boards that would attach to the arduino to do the specific task we need to do.

the project has two essential tasks:

1. control 3 stepper motors and read from either 3 or 6 limit switches. (individual board)
2. control extruders / toolheads. basic stuff: 2/3 motors, a few analog inputs, etc.

i'm thinking that it would make sense to make the stepper controller its own shield.   4 pins * 3 steppers = 12 digital out pins.  i think the limit detectors we could do as analog, so that would either fill half of those slots, or all of them for a full machine.  the motors would be powered externally.

then for the other board, we just have to do a few things: control a few motors, solenoids, thermistors, encoders, etc. for these boards.  these would also be powered externally.

with a beautiful open source project like arduino that exists, it would be a shame to not work together.  the environment, language, and community are all very attractive, as well as the fact that its also an open source project. not only would it benefit us to have a stable platform on which to drive our machine, but it would also benefit all existing arduino owners to be able to take the arduinos they already own, and use them to drive something really cool!

i'm not quite ready to get into the implementing of it, as we definitely have some life left  in our current system.  i'm mainly looking into doing this as the platform for our v2.0 boards.  i just wanted to run the idea past the community, here, and see if anyone likes the idea or is possibly interested in helping out.

if you're interested more in what this project is actually about, check out reprap.org
« Last Edit: September 11, 2007, 10:27:08 pm by Hoeken » Logged

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The Arduino system is a natural for this. I happen to be collaborating with my father on a little project of his to make something very similar to the reprap project. Im sure he will be publishing documentation on this when he is ready but the idea was to make a single board control unit for the cnc aspects of a reprap and have a second daughterboard once the heads and extruders are brought online. I have just completed the first revision of the main board. It runs on a hefty 30A 5V external power source, has 3 uln2003s for onboard control of 5v unipolar steppers, uses a screw terminal for a large heatsinked current limiting resistor, has usb via ftdi's mm232r module, can connect 3 limit switches/photo interrupts, and brings the remaining pins out to headers. Its all through hole so that a kit might one day be offered. This is all in very rough stage at the moment with more information when its available. The only image I have is of the cad file but Im sure my father will post later once he receives the board in the mail and has a chance to get things hooked up. Im already thinking about the second revision and opening it up to variable voltages, finding drivers more robust than the 2003s, having a better interface (switches, rx/tx leds, etc), finding a better implementation of usb and so forth.

Cheers,
Brian

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I'm part of an open source hardware project called RepRap (open source 3d printer), and we're essentially developing a system that relies on a microprocessor to do things.  we're having to solve alot of the problems you've already solved, and it seems sort of silly to re-invent the wheel.  i was thinking that instead of building boards from scratch, we could create shield boards that would attach to the arduino to do the specific task we need to do.


All doo'able with Arduino, you could buy a board and use the example code and throw together a solution with a bit of time and learning.

Pardon my curiosity, have any copies been made that aren't clumpy? I'm not sure if it's because I hit a bad batch of pictures, but the images I have seen of stuff made look as one might expect stacked globs of glue would look.
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It sounds awesome.  Speaking as part of the Arduino team, I think we'd love to work with you.  This sounds like it would make a great Arduino shield, as I'm sure there are lots of people looking to control stepper motors for all kinds of things.  BTW, have you seen the Stepper motor library in Arduino 0009 (http://www.arduino.cc/en/Reference/Stepper)?

As you start to think more about the details, please keep us up-to-date.  

If you have specific questions about the Arduino hardware, or if there's any way we might be able to help with the manufacturing or the distribution of the boards, feel free to contact us at team at arduino dot cc.  If you have any software requests (e.g. improvements or changes to the Stepper motor library), feel free to post in the software development forum or to email the developers list (http://mail.arduino.cc/mailman/listinfo/developers_arduino.cc).  
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Pardon my curiosity, have any copies been made that aren't clumpy? I'm not sure if it's because I hit a bad batch of pictures, but the images I have seen of stuff made look as one might expect stacked globs of glue would look.

well, its definitely still a *research* project.  personally, when i started about a year ago, i knew *nothing* about cnc, 3d printing, etc, other than that it was really cool, and really interesting.  i've made mistakes along the way, but have also learned alot as well.  also, various people in the project have machines in varying states.  some have printed nice things, and others dont turn out so well.  also, some pictures may be extreme closeups... we're working with extruded diameters of 0.5mm.

i'd like to keep this on topic about steppers, but if you'd like to chat more about the project and our goals, feel free to send me a PM.
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It sounds awesome.  Speaking as part of the Arduino team, I think we'd love to work with you.  This sounds like it would make a great Arduino shield, as I'm sure there are lots of people looking to control stepper motors for all kinds of things.  BTW, have you seen the Stepper motor library in Arduino 0009 (http://www.arduino.cc/en/Reference/Stepper)?

As you start to think more about the details, please keep us up-to-date.  

If you have specific questions about the Arduino hardware, or if there's any way we might be able to help with the manufacturing or the distribution of the boards, feel free to contact us at team at arduino dot cc.  If you have any software requests (e.g. improvements or changes to the Stepper motor library), feel free to post in the software development forum or to email the developers list (http://mail.arduino.cc/mailman/listinfo/developers_arduino.cc).  

thanks, and thats awesome to hear!  i've looked at the stepper motor library, and i like it.  one of the major draws of arduino is how easy the firmware is to program.  coming from a C/PHP background its nice and familiar.

there are a few requirements for the board:

1. drive largeish bipolar steppers (and be adaptable to a wide range of motors that people scrounge)
2. do it in the best way possible (eg. the modern, best-practice method of driving steppers)
3. do it as cheaply as possible without compromising the above goals
4. use through-hole and common components wherever possible so that people wont have problems building their own

there seem to be a lot of different options out there for driving steppers, but from what i've read, the 'chopping' style seems to be one of the best.  it supports a wide variety of voltages, and powers the steppers more efficiently and smoothly.  am i correct in this assessment?

i'm not entirely sure what stepper driver configuration i want, but i've been reading this thread, and it seems to be what i'm looking for: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1138310274

it seems the L297 / L298 combo would work very well for what i want to achieve. what do you guys think?

also, on the manufacturing/assembly side, i definitely think we should work together, at the very least i'd love to hear how you guys have done things.  i run the RRRF, or RepRap Research Foundation, which is a non-profit corporation that supports the RepRap project.  essentially we buy and re-sell parts to the community at cost.  i already have experience doing PCB buys, but nothing on the assembly side.  providing a plug and play shield would be AMAZING and be a huge step forward for the community.  but we can figure that all out after the shield gets designed.
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The Arduino system is a natural for this. I happen to be collaborating with my father on a little project of his to make something very similar to the reprap project. Im sure he will be publishing documentation on this when he is ready but the idea was to make a single board control unit for the cnc aspects of a reprap and have a second daughterboard once the heads and extruders are brought online. I have just completed the first revision of the main board. It runs on a hefty 30A 5V external power source, has 3 uln2003s for onboard control of 5v unipolar steppers, uses a screw terminal for a large heatsinked current limiting resistor, has usb via ftdi's mm232r module, can connect 3 limit switches/photo interrupts, and brings the remaining pins out to headers. Its all through hole so that a kit might one day be offered. This is all in very rough stage at the moment with more information when its available. The only image I have is of the cad file but Im sure my father will post later once he receives the board in the mail and has a chance to get things hooked up. Im already thinking about the second revision and opening it up to variable voltages, finding drivers more robust than the 2003s, having a better interface (switches, rx/tx leds, etc), finding a better implementation of usb and so forth.

Cheers,
Brian

hey brian, nice board there.  i definitely want to go the shield route though. in my mind, the whole idea is that the adruino is this microprocessor core, and it has solved all those problems with usb, bootloader, icsp, firmware, etc.  we can essentially consider it a black box, and provide a module that plugs into it in the form of a shield.  that way, when arduino upgrades, we dont have to upgrade our board as well, it can work with any arduino.  also, any of the 10,000 arduino boards out there can easily use our shield.  we've been doing the monolithic stuff for our project, and it just doesn't make much sense to me anymore.
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i'd like to keep this on topic about steppers, but if you'd like to chat more about the project and our goals, feel free to send me a PM.

No worries, I spent a couple of weeks reading everything there was to read about reprap a few months back, so I think I've got a reasonably good handle on the concept.

Good luck!
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also, on the manufacturing/assembly side, i definitely think we should work together, at the very least i'd love to hear how you guys have done things.  i run the RRRF, or RepRap Research Foundation, which is a non-profit corporation that supports the RepRap project.  essentially we buy and re-sell parts to the community at cost.  i already have experience doing PCB buys, but nothing on the assembly side.  providing a plug and play shield would be AMAZING and be a huge step forward for the community.  but we can figure that all out after the shield gets designed.

Cool.  It sounds like a great fit for Arduino.  We'd love to have a shield like this and our goals are very similar (i.e. robust and modern, but cheap and easy-to-assemble).  As for the specifics of the circuit, you're probably best talking with the hardware guys.  They don't always check the forums though so you might want to email team at arduino dot cc (as well as posting here).  
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if anyone is interested in helping out development on this stepper shield, check out this thread: http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1189887306
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