phidget and salvaged parts

to, a complete noob, the electronics are the scariest part of the whole system, as well as the most expensive. I have a proposition that should reduce the cost and make it less complicated at the cost of making it slightly less open source and more cpu intensive. unless there's something obvious I'm missing it should even work.

phidget makes a stepper controller board. assuming this board has enough accuracy to work with reprap it could replace the majority of the electronic. this means that all the servo's have to be controlled by the pc, not just sending an stl file to an arduino. thus more cpu intensive but significantly cheaper. second part is the stepper motors. all scanners and printers have stepper motors, and where I live can be picked up for 6$ at value village. assuming these are strong/accurate enough these could replace almost any motor on the reprap (the phidget control board has 8 slots) no more separate board for the extruder. then we need a temp sensor. a single board usb temp sensor should be fine and cheap. unless there's any electronics I'm missing that should be all.

stepper motor driver +80$ from phidget
stepper motors = 6-12$ from the local used goods store
temp sensor = ???

It's definitely an option for a RepStrap, and if you want to try it I wish you good luck.

The NEMA 17s and tin-can steppers that you find in printers and scanners don't always work out and they aren't going to be able to run quite so fast as the standard 23s but they can be made to work. It should also be noted that salvage can be fickle - there are printers and scanners with only DC motors in them as well, so someone trying to go this route could waste a good bit of money.

The bigger thing is that right now the overall trend of the electronics is moving away from cpu intensive operations - one of the end goals of the Sanguino based electronics is to read GCode from an SD card, no direct communication with a computer necessary. There are a couple of good reasons for that - in the industrialized world, we all have computers, but that doesn't mean we want to have to dedicate them to running our 3d printer and not available for use while printing, whereas in the developing world having to dedicate a powerful computer to running the printer could be a deal breaker, but anything with a text editor can technically be used to produce GCode manually. It's also more in keeping with self-replication to have standalone electronics. We might someday soon be able to make the PCBs for a new Sanguino, and even put down soldering paste - and some people are working on pick and place systems as well. Building an entire computer, on the other hand..

Also you did miss the endstops but those are not the hardest thing in the world to interface to a computer either.

For a repstrap, though, the phidget board is definitely a workable concept. I think you were looking at the RC servo board though, the Unipolar stepper driver board I see on there only has 4 ports - still enough for a reprap, though. If you wanted to use all phidget boards, the 8/8/8 interface board combined with the unipolar stepper board could run a whole reprap no problem. That comes out to $155, though.

I've worked a lot with tin can steppers. You aren't going to be able to use them with a belt-driven Darwin design but they can be made to work with lead screw designs as long as you are careful not to make your positioning stages too heavy. Mind, if they are drawing less than 0.4 amps/phase at 12v you're going to have trouble getting enough torque out of them for anything practical.

Insofar as stepper board controller costs go, the break point is about 1 amp/phase. There are a variety of good, cheap controller chips like the old 754410 that will handle up to about 1 amp/phase. Once you go past 1 amp, however, you're into L298N and heavier territory. Those chips carry pretty heavy currents and can make lots of magic smoke and sparks if you get the wiring wrong. I know from personal experience that an L298N without a big heat sink on it can fry a fingerprint off if you touch it at full load. Stay below 1 amp/phase and you don't get into trouble like that.

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Hell, there are no rules here - we're trying to accomplish something.

Opportunity is missed by most people because it is dressed in overalls and looks like work.

Thomas A. Edison

i have started work on this idea my self, i have a scanner or 2 and i have a couple printers i need to grab from storage, and i was thinking about Hijacking any boards / chips i need (or rather anything i can!) from the electronics because the electronics is the most expensive part.

I have already deduced(just had time to look at them once) that i can drop my cost massively, because of that Large amount of components in the scanners. just one of them has the a Belt, 2 pulleys, the Stepper (if its not powerful enough a reduction drive could give it more torque and the Rep(St)rap would run slower), and a Several Chips/Resistors/capacitors and other little things found in the electronics.

Then I'm going down to Home Depot, or ACE Hardware (any hardware store) and using a similar design to the "McWire Cartesian Bot v1.2" Unless the person near me gets his RepRap printing parts soon.

With that, all I need to find is a supplier for the PTFE and concoct a make shift extruder.

Pretty easy in theory, and where their a will there a way.