Which motor/sensor setup to make

Hello. I was asked to build a machine which basicly consists of two parts - a paper feeder and a part that folds the paper on certain parts. I made a working prototype using lego mindstorms 2.0 and now i'm hoping to make one using arduino. The lego model knew when to fold the paper using the built-in rotation sensor. So i want to ask, should i use a stepper motor (could be too slow) or a regular dc motor with some kind of rotation sensor for arduino (if it exsists)? I thank you for your help.


Tell us a little more about this machine. How many (or less than 1?) rotations of (what) does it take for these motions?

Can you recheck some starting position before each "operation"??

Stepper motors can do precise positioning over several revolutions.

DC motors would need some added rotation sensor.

In both cases you need another switch or sensor to always find the same "start" position.

A simple rotation sensor is a disc with slots or holes and an "optointerrupter". Example: http://arduino-direct.com/sunshop/index.php?l=product_detail&p=202

DISCLAIMER: Mentioned stuff from my own shop...!

First of all, thank you for your reply.

Well it's pretty simple really. Feeder feeds a new sheet of paper into the second part. This one first pushes the paper to a blocked exit, thus aligning it and making sure all papers start at the same position. Then it unblocks the exit and motor with rotation sensor follows a program that goes something like this: rotate 20°, activate folding. rotate 45°, activate folding and so on, until whole paper is done. Then the process starts over again. Yeah i was thinking on salvaging old mouses for optointerrupters, but now that i think of it, a stepper motor from an old printer could do the trick. I just wonder how precise they are, since the whole folding operation depends on stepper motor rotations...

Hi, Sounds like a stepper motor with enough torque to not miss any steps would work. Then in software you can finetune the number of steps for each action to get the mechanical movement you want.

Goes this part then reverse to starting position, or rotate forward to the start again?

Hello again.

Well in the lego prototype, the same motor fed the paper that came from the feeder and also managed the precise turning part. I was hoping to do the same thing here, since it is simpler. So yeah, it spins until the paper is aligned, then stops and starts the precise turning. So it allways turns just in one direction. If a stepper motor should suffice, all i need to know now is which arduino should i get? It has to be able to drive a stepper motor, a regular dc motor and one or two other servos + an IR barrier sensor. I don't want to get an overpowered arduino, or one that can't cope with this, so something inbetween. Also, are there shields that already exsist for driving stepper motors, servos etc? Thanks