S.O.S. - arduino class project - what to buy?

[TeacherVince]

I have posted a link to my request for help from the ARDUINO community, here: https://docs.google.com/document/d/1Le3 ... sp=sharing

Hello Arduino community. My name is Vincent Benard O.C.T. and I need your help.
I am introducing Arduino into my Design Technologies course this year and I have some questions for you. I hope you can help me out?

My students are creating Arduino controlled dispensers (a cat food dispenser, a pencil dispenser and a coin dispenser). Each dispenser will have an Arduino controlled mechanism incorporated into it.

The motion/movements will be: reciprocating/linear (coin dispenser dispenses by a moving slide, like a pusher), pencil dispenser has a rotating cylinder with 4 pencil slots in it (rotating motion, 90 deg at a time) and the cat food dispenser has a rotating Archimedes screw (number of rotations adjusted to dispense proper amount of food).

My forte is mechanics, not electronics. I can easily get the mechanics working but my questions are about the electronics end of the projects.

In many Arduino FAQ’s Blogs, Forums, there is talk about “SHIELDS” for motor control. In the Arduino kit that I purchased, there is no shield, just two motors and they work fine as is.

1.Can I use Arduino kit motors to activate the different mechanisms or do I need stronger motors?

2.Can as many as 5 “hobby motors” be added to an Arduino UNO (each one controlled/cycling, one at a time - when a button is pressed)?

3.Can you recommend a suitable motor (specs or part number) that could be used in the projects?

4.Is a “shield” or motor controller necessary for the motors you recommend? If yes, can you recommend a suitable item?

As for programming, I believe I can find suitable code in the Arduino files or on the web.

Please provide your answers/suggestions below. Feel free to leave your contact info (email) if you’d like.

Thanking you in advance,

Vince Benard O.C.T.

[Franklin97355]

Question 1 and 3 What torque do you need to move the items and what mechanical advantage can you provide. All of what you want to do can be accomplished with the right mix of parts but we need more precise information or you need to do more research into the capabilities of the parts you plan to use.

[TeacherVince]

Hmmm, good question. The coin dispenser will use a crankshaft type of mechanism (think of a piston in a cylinder) The slide will dispense one coin at a time (from a stack of coins). Force requirement unknown. I imagine only a few Newtons. The pencil dispenser will be a rotating drum (toothed belt driven pulleys or worm gear) and the cat food dispenser will be a Archimedes screw driven by a stepper motor or worm gear. In hand turn tests, we find that there is potential for pieces of food getting caught in the screw. Mods are being done to the design to avoid/reduce this.

Hope this helps?? And thanks for replying. :)

[Franklin97355]

The motor shield should work for you in your steppers are 10 ohm or more per phase. You can also use DC motors if you add a transistor or MOSFET. Check out the tutorial here. or here