Looking for a micro-controller

[Mariana Cardoso]

Hello Everyone!

I am looking for a micro-controller much like an Arduino but with
several (if possible a lot) of output pins (if possible analog, but
digital could work too).

Affordable and easy to code suggestions?

THANKS!!!
mariana

[Darcy Whyte]

Arduino Mega?

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[Mariana Cardoso]

Thanks! That might be an idea, although i was looking more for
something with a few hundreds of outputs...

[Joseph Pizzo]

Hi, you can extend arduino... Take a look at this:

http://www.arduino.cc/en/Tutorial/ShiftOut

[raphael]

Any reason why I can't run a universal series motor (in this case a
vacuum cleaner) through a variable transformer to control its speed? I
tried it and it worked really well, but maybe there's some kind of long
term danger/inefficiency?

[Kevin Anthony]

If your trying to control the speed wouldn't a variable resistor work better?

Kevin
Please excuse brevity, sent from phone

On Oct 24, 2011 12:55 PM, "raphael" <rap...@teuthis.com> wrote:

Any reason why I can't run a universal series motor (in this case a vacuum cleaner) through a variable transformer to control its speed? I tried it and it worked really well, but maybe there's some kind of long term danger/inefficiency?

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[raphael]

No, a variable resistor would generate a dangerous amount of heat. We
would be dissipating hundreds of watts if we did it that way.

Hopefully, by lowering the voltage with a transformer, we also lower the
current going through the motor and thus the total wattage and so the
torque. The torque pushes against the air, which ultimately regulates
the speed. Right? I'm pretty sure that the variable transformer is going
to work, I just like to have peer review on my crazy ideas!

On 10/24/2011 01:11 PM, Kevin Anthony wrote:
> If your trying to control the speed wouldn't a variable resistor work
> better?
>
> Kevin
> Please excuse brevity, sent from phone
>
> On Oct 24, 2011 12:55 PM, "raphael" <rap...@teuthis.com

> <mailto:rap...@teuthis.com>> wrote:
>
> Any reason why I can't run a universal series motor (in this case a
> vacuum cleaner) through a variable transformer to control its speed?
> I tried it and it worked really well, but maybe there's some kind of
> long term danger/inefficiency?
>
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[Eduardo Artigas]

There are many complications in controlling the speed of a universal motor with a variable transformer or better, electronically.

1) The motor cooling fan generates much less cooling at lower speed and the motor may not have been designed to work with less cooling air.

2) Power. As you reduce the speed the power delivered by the motor is less, with the electronic control it can be compensated as well the speed can be electronically stabilized for when the motor is making a bigger effort will slow it down.

3) A resistor is no option, since it will dissipate in heat all the power not taken by the motor and that can be a lot (here I am super simplifying.) 

Hope it helps. You can buy an electronic control sold for tools and works with universal motors (very cheap) but the cooling and speed stabilization issue still is there.

Ed

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[raphael]

How do those work, like a lighting controller? Or are there smart things
in there?

So far the motor seems to be keeping cool, but I'll run an extended
test. As for power, that's fine. I actually want to reduce power since
the amount of air moved seems to be proportional to power.

Thanks!

(By the way, the big unspoken advantage to the variable transformer is
the HUGE and AWESOME knob on top for control!)

On 10/24/2011 01:22 PM, Eduardo Artigas wrote:
> There are many complications in controlling the speed of a universal
> motor with a variable transformer or better, electronically.
>
> 1) The motor cooling fan generates much less cooling at lower speed and
> the motor may not have been designed to work with less cooling air.
> 2) Power. As you reduce the speed the power delivered by the motor is
> less, with the electronic control it can be compensated as well the
> speed can be electronically stabilized for when the motor is making a
> bigger effort will slow it down.
> 3) A resistor is no option, since it will dissipate in heat all the
> power not taken by the motor and that can be a lot (here I am
> super simplifying.)
>
> Hope it helps. You can buy an electronic control sold for tools and
> works with universal motors (very cheap) but the cooling and speed
> stabilization issue still is there.
>
> Ed
>
> On Mon, Oct 24, 2011 at 1:11 PM, Kevin Anthony
> <kevin.s...@gmail.com <mailto:kevin.s...@gmail.com>> wrote:
>
> If your trying to control the speed wouldn't a variable resistor
> work better?
>
> Kevin
> Please excuse brevity, sent from phone
>
> On Oct 24, 2011 12:55 PM, "raphael" <rap...@teuthis.com

> <mailto:rap...@teuthis.com>> wrote:
>
> Any reason why I can't run a universal series motor (in this
> case a vacuum cleaner) through a variable transformer to control
> its speed? I tried it and it worked really well, but maybe
> there's some kind of long term danger/inefficiency?
>
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[Dan Lavin]

Variable transformers (aka Variacs) are big and expensive, but should
work fine -- subject to the low speed cooling issues noted.

Electronic controllers essentially are light dimmers and are smaller and
cheaper. They can also be electrically noisy and will burn out quickly
if overloaded, and the motor cooling issue is the same.

Since you already have the variable transformer, stay with it.

[Neil Cherry]

On 10/24/2011 02:02 PM, raphael wrote:
> How do those work, like a lighting controller? Or are there smart things in there?

A lot of light controls use SCRs, don't use dimmers with motors!

--
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http://www.linuxha.com/ Main site
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Author of: Linux Smart Homes For Dummies

[Eduardo Artigas]

You can see one here, a very cheap model:

http://www.harborfreight.com/router-speed-control-43060.html?utm_medium=cse&utm_source=googlebase&hft_adv=40010&mr:trackingCode=146B0F9E-782A-E011-B31E-001B2163195C&mr:referralID=NA

The work by regulating how long during the AC cycle the power is on. Super simplified version. Shorter periods gives slower speeds.

Ed

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[Matt Joyce]

It's like the angry electricians equivalent of PWM.

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[Nick Vermeer]

One major difference between a light dimmer and a universal motor speed controller is that a dimmer logic is powered through the load, rather than in parallel.  This means the load is never fully off if the logic is still on. This can lead to dangerous voltages being present on a load that appears to be fully off.  The current limit of the logic is still high enough to be hazardous to the unprotected.

Also, doing waveform chopping for speed control puts a much higher pulsed current through the windings than a normal sine wave.  The quick rise time of the truncated wave causes an inrush current that can cause a failure of the windings.  Recently (last 10 years or so) motors now have classifications of "inverter rated" to handle this.

All of this is avoided with the Variac.  As long as the motor is sufficiently cooled, you can speed control it to your heart's content. A Variac is not safe when used with frequency synchronous motors, but that's not an issue here. To be sure you have a universal motor, you should confirm that you can run it on DC as well as AC.

The solid state speed controller that can handle almost any motor type is the high frequency  IGBT inverter.  These are just H bridges (or 3 phase bridges) using IGBT's, and can handle high voltages and high currents while controlling both frequency and amplitude of the output waveform(s).