[Cialug] Arduino winners

[Matthew Nuzum]

On Fri, May 18, 2012 at 9:00 AM, Morris Dovey <mrdovey at iedu.com> wrote:

> If anyone is contemplating using their Arduino for complex control
> applications, I have a set of small functions that provide cooperative
> (non-interrupt) multi-tasking, timekeeping (usec uptime /and/ usec of the
> epoch), and usec task scheduling for as many tasks as you can shoehorn into
> your machine's memory.
>
> They're not open-source, but they're free of charge for personal
> exploration and use.
>
> If interested, contact me a note off-list and I'll e-mail C sources.
>
>
Just an FYI, Radio Shacks around town stock some Arduino addons that can be
fun to play with.
http://www.radioshack.com/search/index.jsp?kwCatId=&kw=arduino&origkw=arduino&sr=1

There is a $17 shield prototyping kit, motor shields and SD shields.

They also have a two-axis accelerometer that looks fun:
http://www.radioshack.com/product/index.jsp?productId=2909788

If you want to control high-powered stuff (that needs more than about 40ma)
you can get a darlington pair which looks and works a lot like a transistor
but is more "digital" in that it is either all the way on or all the way
off (that is a gross oversimplification). They have some of those at Radio
Shack too.

Another thing to remember about microcontrollers is that they tend to be
better at sinking than sourcing. So instead of hooking your light or motor
up so that when you turn a digital port "on" that current flows through to
the led/motor and then to ground (let's just skip the discussion about
which way current flows), in other words your Arduino is the power source,
you should instead have your device connected to power and then let the
current flow through it, through the micro and to ground when you switch
the port to 0, so conceptually your arduino is the ground.

It feels like inverted logic because now 0 is on and 1 is off but it makes
it much less likely for you to burn the device out. It's easy to do.
Believe it or not, even many power transistors require too much current to
be controlled from the arduino. You need a low current transistor to
control the power transistor (which effectively multiplies your gain and
gives you a darlington pair).

I mention this because Radio Shack does have some cool stuff to play with
there. For example, light sensors, infrared motion sensors (Parallax PIR)
and more. Also, if you have old computer junk around you can salvage some
cool parts. For example, IBM 5 1/4 floppy drives have some nice and easily
hackable stepper motors in them.

-- 
Matthew Nuzum
newz2000 on freenode, skype, linkedin and twitter

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