12V input

Question about power
YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

12V input

Post by YahooArchive » Thu Oct 25, 2012 2:42 pm

>I see that it has a 5v output point but this is only
> good for 500mA and not very efficient due to the losses from the
> regulator. (from 12V)

The ARMmite that is currently shipping uses a 5V main regulator, in
November that will change to a 3.3V regulator (same as the wireless
version). With the 3.3V regulator an input of 4.5V or more is
required and it need not be regulated.

You may attach 5V regulated supply to the output of the current
ARMmite regulator, though its not the most convenient connection.

If your project is only connected to USB for programming, you might
consider switching to an ARMmite wireless and use the USB adapter
(from SparkFun) for programming.

For reference both ARMmites use about 50mA.



brucee
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Re: 12V input

Post by brucee » Wed Oct 31, 2012 2:34 am

> I just received my Armmite Evaluation board. I am looking for an easy
> way to power it.

The ARMmite can get its power from the USB connection.

> Can I purchase an off-the-shelf power unit from Radio Shack or
> elsewhere that will plug into the ARMmite board and supply the
> necessary power?

When not running connected to a PC via USB, the ARMmite can get its
power from most any wall wort. But the voltage should be 6-7V if
unregulated, or a 5V regulated supply. SparkFun carries the regulated
ones, and Radio Shack will have unregulated ones. The outside is GND
and it is a 2.1mm barrel connector which is the most popular power
connector in the US these days.

If your project will not be connected to a PC in normal use, the
wireless ARMmite is a good board to use, even if you don't run it
wirelessly. While programming you can use a FT232RL USB breakout
board from SparkFun, and disconnect it when placed into the application.

YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:02 pm

>from help line
> I need to use a 3 cell Lithium Polymer battery for my
> application (using the Armite Pro) and at full charge these
> packs are 12.6V. I know the board is rated for 6-12V input.
> Can I use this or do I need to do something to drop the
> voltage below 12V?

While it would work, you would be wasting 1/2 W in the regulator. If its in an
enclosure its thermal regulation could kick in and it would shutdown.

Best would be to use a switching regulator to generate the 5V.

We've been thinking of doing a board with that regulator and targeted to a
specific enclosure with prototyping area and connectors for the Arduino/PRO
footprint.

So we're looking for some suggestions for what else might be on that board and
what type of enclosure to use.

YahooArchive
Posts: 1463
Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:06 pm

http://www.national.com/mpf/LM/LM2575.html

Very easy to work with.

don

YahooArchive
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Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:07 pm

Hi Bruce,
I thought that was the minimum Vcc of 6V.
Everything works with 5 volts without degraded performance?
With 5 Vcc, the VREF of 3.3V remains 3.3V?

YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:08 pm

Bruce,

In addition to easy 12V. and 5V operation, the enclosure should have
interchangeable front & rear panels with different I/O configurations. These
would allow for 9, 16, or 25 pin Sub D connectors, or Din Connectors, as well as
USB connector. Also a few LED's to indicate Power On, and user programmed
indicators. A power On/Off switch should also be an option.

The board should have header pins to easily accomodate this I/O.

YahooArchive
Posts: 1463
Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:08 pm

> I thought that was the minimum Vcc of 6V.
> Everything works with 5 volts without degraded performance?
> With 5 Vcc, the VREF of 3.3V remains 3.3V?

In this case the 5V regulator of the PRO would not be used, and the output of
the switching regulator tied directly to the 5V supply line.

The 3.3V regulator would run as normal of the 5V inmput

YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Mon Feb 04, 2013 8:09 pm

> Very easy to work with.

We use the LM2574 in the DINkit, like the 2575 very easy to use, and I doubt
many would really need the 1A for the 5V supply.

But we are shopping for a plastic clamshell enclosure. We have used the Hammond
Al extrusion cases in the past, and could stick with those. Using a Polycase LP
series for a new wireless design. And SparkFun's case is about the right size
(but only has 1 insert for IOs)

So forward any suggestions in the 3x5" range

YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Sun Feb 10, 2013 11:32 pm

Greetings,

I recently got an ARMmite and began playing with it.
I have had a rather unfortunate event happen to my ARMmite board.
I utilized a 12VDC wall wart and now some of the IO pins are dead.

I suppose it would not regulate properly. This leads me to the question. If I
want to power it up with a motorcycle, or wet/dry lead acid battery (not in a
running car but as the power source), then those batteries when fully charged
are ~12.9V, and they discharge to about ~11.6V (at that point we have a shut-off
so we don't dicharge them too much for us to recharge).

So can these boards handle very gradual changes in DC (over several hours, or
days) between those ranges?? Do I need to put that through a separate
12VDC-12VDC regulator circuit? (Seems inefficient) Please advise, thanks.

-T

YahooArchive
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Joined: Fri Oct 19, 2012 5:11 am

Re: 12V input

Post by YahooArchive » Sun Feb 10, 2013 11:34 pm

> I recently got an ARMmite and began playing with it.
> I have had a rather unfortunate event happen to my ARMmite board.
> I utilized a 12VDC wall wart and now some of the IO pins are dead.

A 12V wall wart could easily be putting out 18V or more with a light load. With
cheap 5V regulated wall warts that are for USB devices, its better to go with
one of them.

Just running off a 12V supply even a noisy one in a car/motorcycle wouldn't kill
IOs. If the IO goes above 5V or below ground that can take it out.

I'm working on a board aimed at the auto market with a specific customer in
mind. While 12V could be used with some protection from spikes, it throws a lot
of power away.

One of these modules looks like a good solution.

http://www.murata-ps.com/data/power/oki-78sr.pdf

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