Microcontrollers and embedded processors
Nathan Smith
What are the names of some of the micro controllers and embeded
processors everyone was tossing about last night? I know BASIC stamp,
but I don't think I knew any of the others. Oh, I just notices on the
list Atmel and Arduino. I wish the list subject-lines were mailman-like
and had a [robotics] tag in the subject line.
And Briefly, what is a stepper motor? It moves in small increments? Is
the motion indexed somehow? I think they are used in hard drives and
floppy drives, what other common things use stepper motors?
-Nate
Dan Hockey
you will find lots of stuff about steppers
On Jul 10, 11:05 pm, Nathan Smith <nathan.sm...@rockinghamridge.com>
wrote:
Matthew Nuzum
Smith<nathan...@rockinghamridge.com> wrote:
> What are the names of some of the micro controllers and embeded
> processors everyone was tossing about last night? I know BASIC stamp,
> but I don't think I knew any of the others. Oh, I just notices on the
> list Atmel and Arduino. I wish the list subject-lines were mailman-like
> and had a [robotics] tag in the subject line.
The common ones for hobbiest are Basic Stamp, Propeller and SX from
Parallax, Pic 12 (8 bit) Pic 16 (8 bit) and pic 24 (16 bit) from
Microchip, AT Tiny and AT Mega from Atmel and PicAxe. There are many
others, freescale being a notable option, that don't have a big
emphasis on the hobbyist market. Here's a rundown:
* Parallax products are very hobbyist friendly - easy manuals,
development tools are free but the products tend to be quite expensive
relatively speaking. Low learning curve. Windows only development
environment
* Microchip products are very popular because they'll send you free
samples of the parts. Their products are designed to be programmed
using assembler but some free development tools are available. Huge
variety of parts and the starting price for an entry level micro is
about $0.60 each. Dev tools are expensive, mostly windows only. You
need a hardware programmer such as the PicKit2 Starter Kit
* Atmel products are very cheap (starting at about $1.00 for entry
level part) and have a huge variety. Designed to be programmed in C
and free (GCC) based development tools for a variety of platforms.
Needs a hardware programmer like the ladayada product I mentioned
yesterday.
* PicAxe are pics pre-programmed w/ a basic interpreter (like the
basic stamp), quite cheap. I've never used them but they're gaining in
popularity for hobbyists.
Arduino is a pre-configured platform (like the basic stamp boards)
built w/ Atmel microcontrollers. It can be programmed using USB. It
costs from about $20 to $35 per board.
To be clear, a microcontroller is a tiny embedded computer (usually)
w/ flash memory that you download pre-compiled code to. It has several
inputs and outputs and may have more advanced peripherals such as PWM
and/or networking capabilities (like serial, i2c, can).
> And Briefly, what is a stepper motor? It moves in small increments? Is
> the motion indexed somehow? I think they are used in hard drives and
> floppy drives, what other common things use stepper motors?
A stepper is an interesting motor. It has two coils and you have to
energize them in a specific order to get them to turn a few degrees.
If you want them to spin continuously you have to feed them two sine
waves slightly out of phase. This is uncommon, instead people use PWM
to move the motor in smaller increments. This is called micro
stepping. A typical stepper moves 1.8 degrees per pulse so 200 steps
for one rotation.
There are two types, unipolar (which are a little easier to start w/
but really no better once you figure them out) and bipolar. A unipolar
has 5 or 6 leads but if you ignore one or two of them you can treat it
exactly like a bipolar motor which has 4 leads.
It does not provide any feedback (per se) so the device rotating the
motor needs some other means to detect movement.
--
Matthew Nuzum
newz2000 on freenode, skype, linkedin, identi.ca and twitter
Randy M. Dumse
Forth and robotics have gone hand in hand for many years. New
Micros, Inc., sell products based on Forth and good for
robotics, particularly PlugaPods(TM), IsoPods(TM), and
ServoPods(TM). (I own NMI by the way.) Forth, like BASIC was
originally, is interactive. So if you want to try something, you
just type its name and it runs. So it is really easy to debug.
I've added state-machines to my version, now called IsoMax(TM)
and multitasking abilities. You can visit my web site if you are
interested.
We use these PlugaPods(TM) boards in a Mini-Sumo class Dr. Dale
Olson and I teach at UNI (my Alma Mater). We host the first ever
invitational Mini-Sumo Ship-In contest once a year. We invite
people from around the world to ship in their mini-sumos to
compete against others and our students. We webcast the video,
so owners can watch and see how their robots did. We've been
doing that for 4 years now, and it grows every year, and brings
Iowa some international robotics notoriety.
> And Briefly, what is a stepper motor?
Stepper motors are motors without brushes, that usually have
multiple windings and internal rotor polarizations, so if the
voltage applied to their windings changes, the rotor moves in
small incremental steps. Usually these rotations are small, a
few degrees. By then changing the voltage on the windings again,
it will take another step, and so on.
Steppers are heavy, but rugged, easier to control than a brushed
or brushless motor. (In fact they are a certain kind of
brushless motor.) Usually they can be controlled "open loop" or
without an encoder to read their position back. You just pulse
it so many times in sequence, and if they rotor isn't extremely
resistant, the rotor will follow the pulsing. (Although they can
slip.)
Actually the most favored site for refering people to explain
steppers is a U-of-I site by Douglas W. Jones.
http://www.cs.uiowa.edu/~jones/step/index.html
Randy M. Dumse
www.newmicros.com