Powering a GSM cellular shield

[Chris Clearfield]

Hey,
I've been working on a project that will make use of a GSM cellular
shield (http://www.sparkfun.com/products/9607). It's been going fairly
well, but I have a question about powering the device that I haven't
quite been able to figure out.

The shield can be powered by the arduino itself, but during high loads
(e.g., while transmitting), it can draw up to 2amps, more than the
arduino can provide. So, it's recommended that it be powered
"independently." I'm not sure what this last thing means. It seems
like the shield hooks into V_in from the arduino.

Should I just hook up the barrel jack of the arduino to an
appropriately rated wall wort? What should the voltage of the wall
wort be? Can I still plug USB into the computer to communicate with
the arduino while having it powered by the wall wort?

Any advice appreciated.

Thanks,
Chris

--
Chris Clearfield

[c f]

You need to make sure that you can supply enough current to all of the devices under peak conditions. If your arduino has an on-board voltage regulator chip (say, that allows you to plug in a 5-9V wall supply, and produces either 5V or 3.3V to actually run the chip), then you can look up the data sheet to see how much current it can safely supply. You also need to make sure that your wall supply can also source enough current to supply the voltage regulator.

If you are powering the GSM module from the arduino's onboard regulator chip, it probably can't actually source 2A. In that case, you would need to make sure that the GSM module does not share a "V_in" with the arduino (even though they do still need to share a ground wire), and that it is powered by another, dedicated voltage regulator that can supply enough current. Many voltage regulator chips are available that you could hook up to a wall supply to power the GSM module.

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[Guan Yang]

On Tuesday, December 13, 2011 at 10:15 , c f wrote:
> If you are powering the GSM module from the arduino's onboard regulator chip, it probably can't actually source 2A. In that case, you would need to make sure that the GSM module does not share a "V_in" with the arduino (even though they do still need to share a ground wire), and that it is powered by another, dedicated voltage regulator that can supply enough current. Many voltage regulator chips are available that you could hook up to a wall supply to power the GSM module.

What exactly happens if you take an Arduino (without any shields) and plug in both a 9V wall wart and a USB cable? Are the 5V from USB and the 5V side of the regular just tied together? Is there a switch ensuring that only one power source is used?

[michael lowry]

If your application has a GSM cellular shield, are you planning on having it be mobile? in which case, the wall wart method will only serve you sitting in one place, and not on the go. 

As far as the Arduino power selection, it depends on the model board you have. The newer Uno boards i know for sure select the power source automatically, and don't skip a beat when, for example, a USB cable is powering it and you plug a battery into the barrel jack and then remove the USB cable (and vice versa). (Older boards may have a movable jumper to select USB or External power.)

I see on the sparkfun site that the shield itself has a dedicated voltage regulator (SPX29302). Before considering an additional regulator, take a look to see if this regulator simply takes the Vin from whatever battery and modifies it. (Schematic: http://www.sparkfun.com/datasheets/DevTools/Arduino/cellular%20shield-v12.pdf). If this is the case, then maybe all you need is a battery with enough mAH to supply the peak loads.

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Michael Lowry
Research Assistant

NYU Minimally Invasive Surgery Lab

423 E 23rd Street, New York, NY 10010

Office: (212) 686-7500 X6441
Cell: (201) 787-8633

mt...@njit.edu

[Chris Clearfield]

Hi Michael,
It actually will be static, not mobile (but in a place with no
phone/internet). The shield does have a voltage regulator on it,
though I haven't quite been able to figure out the input tolerances
(http://www.datasheetcatalog.org/datasheet/sipex/SPX29300T-2.5_TR.pdf
-- I believe it's 16V as the maximum).

I have a Rev2 uno. I think that the voltage regulator in the shield
takes its input from the Uno's VIN. But, I need to check this. It's
ambiguous from the arduino docs what that power pin puts out when
running off of USB (http://www.arduino.cc/en/Main/arduinoBoardUno,
"VIN. The input voltage to the Arduino board when it's using an
external power source (as opposed to 5 volts from the USB connection
or other regulated power source). You can supply voltage through this
pin, or, if supplying voltage via the power jack, access it through
this pin.")

I'll take a look at it when I'm at home.

Thanks,
Chris

--
Chris Clearfield

[Dan Lavin]

Looking at the schematic, the module has its own voltage regulator.
From the picture it looks like the regulator is connected to Vin on the
Arduino--VERIFY THIS--so the module will be powered without its power
going through the Arduino's regulator. The module does not appear to
even connect to the Arduino's +5 or +3.3 lines. As a result you can use
a 2 amp wall wart.

Check the data sheet on the regulator for voltage limits, but I expect
that something in the 6-12 volt range should work. Remember that the
output voltage of unregulated wall warts is often not as labeled, so
check under load.

[michael lowry]

The particular regulator in mind is spec'ed out as a 3 Amp regulator, so this should work handily. Double check the datasheet, but that's what i found with a quick search. (http://www.datasheetcatalog.org/datasheet/sipex/SPX29300T-2.5_TR.pdf)

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[Chris Clearfield]

Thanks all. I will check all this stuff tonight.
--
Chris

>> nycresistormi...@googlegroups.com.

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>
>
>
> --
>
> Michael Lowry
> Research Assistant
>
> NYU Minimally Invasive Surgery Lab
>
> 423 E 23rd Street, New York, NY 10010
>
> Office: (212) 686-7500 X6441
> Cell: (201) 787-8633
>
> mt...@njit.edu
>
>

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Chris Clearfield

[Chris Clearfield]

Hey,
The shield does in fact take from Vin, so I've ordered a wall wart to
get this hooked up.

Thanks everybody for the suggestions.
Chris

--
Chris Clearfield

[michael lowry]

Best of luck on the project. Let us know how it works out =]

[mattq...@gmail.com]

Hope this evening finds everyone well.

In the process of trying to swap out a shattered screen on an Iphone I've unfortunately stripped a screw head. It's one of the internal screws, extremely small. I was curious, does anyone know where to find a tap and die set small enough to tap into one of these screws?

Cheers,
Matt

---

From: michael lowry <mt...@njit.edu>

Sender: nycresistormi...@googlegroups.com

Date: Fri, 16 Dec 2011 16:42:41 -0500

To: <nycresistormi...@googlegroups.com>

ReplyTo: nycresistormi...@googlegroups.com

Subject: Re: [NYCR:Microcontrollers] Powering a GSM cellular shield

[Neuro8]

I don't know off hand, but you could call Dr. Brendan for what tool-
set they use (and post back about what it was!) Their iPhone repair
has saved me from 2 cracked screens (I'm really unlucky with my
phones...)

http://drbrendan.com/

> > >> m...@njit.edu

> m...@njit.edu

[Bill French]

If you stripped the head, what were you hoping to accomplish with a
tap and die set? Are you thinking of an "easy out" or extractor set?
Amazon has some:

http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dtools&field-keywords=micro+screw+extractor&x=0&y=0

-- this looks promising:
http://www.amazon.com/58-0670-6-Piece-Extractor-Reversible-Driver/dp/B000JCT3W0/ref=sr_1_1?s=hi&ie=UTF8&qid=1324225479&sr=1-1

.. having never opened an iphone before, so take this for whatever
it's worth, my gut instinct is to drill the head off with a drill and
small bit and replace the screw.

On Dec 17, 10:34 pm, mattqui...@gmail.com wrote:

> Hope this evening finds everyone well.
>
> In the process of trying to swap out a shattered screen on an Iphone I've unfortunately stripped a screw head. It's one of the internal screws, extremely small. I was curious, does anyone know where to find a tap and die set small enough to tap into one of these screws?
>
> Cheers,
> Matt
>
>
>
>
>
>
>

> -----Original Message-----
> From: michael lowry <m...@njit.edu>

> Sender: nycresistormi...@googlegroups.com
> Date: Fri, 16 Dec 2011 16:42:41
> To: <nycresistormi...@googlegroups.com>
> Reply-To: nycresistormi...@googlegroups.com
> Subject: Re: [NYCR:Microcontrollers] Powering a GSM cellular shield
>
> Best of luck on the project. Let us know how it works out =]
>
> On Fri, Dec 16, 2011 at 3:04 PM, Chris Clearfield <
> chris.clearfi...@gmail.com> wrote:
>
> > Hey,
> > The shield does in fact take from Vin, so I've ordered a wall wart to
> > get this hooked up.
>
> > Thanks everybody for the suggestions.
> > Chris
>
> > On Tue, Dec 13, 2011 at 4:37 PM, Chris Clearfield
> > <chris.clearfi...@gmail.com> wrote:
> > > Thanks all. I will check all this stuff tonight.
> > > --
> > > Chris
>

> > >> m...@njit.edu

> m...@njit.edu

[Robert L Cochran]

iPhones use pentalobe screws in some places and you need the right
fastener head or screwdriver to avoid problems. I'm not a master of
extracting screws that have stripped out heads, but it might be possible
to find tips on http://www.ifixit.com/

I have iFixit's "version 1" 54-piece toolkit and it seems to work very
well if the screw or whatever is not frozen solidly into whatever it is.
For those I need beefier screwdrivers that let me exert more twisting
force -- I tend to like Wiha drivers for that, but I'm not sophisticated
with tools, either. I think it is worth the cost for me to buy their new
toolkit which just came out. I do work with small devices. Not as small
or as specialized as a watch...my hands shake way too much.

Check iFixit's teardown and repair manuals before trying to disassemble
small electronic devices. Reading what is on the iFixit site is well
worth the time. I just wish their videos are closed captioned. The
teardown photos usually tell me a lot, but I always wonder if I'm
missing something from the videos.

Bob Cochran

On 12/17/11 10:34 PM, mattq...@gmail.com wrote:
> Hope this evening finds everyone well.
>
> In the process of trying to swap out a shattered screen on an Iphone
> I've unfortunately stripped a screw head. It's one of the internal
> screws, extremely small. I was curious, does anyone know where to find
> a tap and die set small enough to tap into one of these screws?
>
> Cheers,
> Matt

> ------------------------------------------------------------------------
> *From: * michael lowry <mt...@njit.edu>
> *Sender: * nycresistormi...@googlegroups.com
> *Date: *Fri, 16 Dec 2011 16:42:41 -0500
> *To: *<nycresistormi...@googlegroups.com>
> *ReplyTo: * nycresistormi...@googlegroups.com
> *Subject: *Re: [NYCR:Microcontrollers] Powering a GSM cellular shield

>
> Best of luck on the project. Let us know how it works out =]
>
> On Fri, Dec 16, 2011 at 3:04 PM, Chris Clearfield
> <chris.cl...@gmail.com <mailto:chris.cl...@gmail.com>> wrote:
>
> Hey,
> The shield does in fact take from Vin, so I've ordered a wall wart to
> get this hooked up.
>
> Thanks everybody for the suggestions.
> Chris
>
> On Tue, Dec 13, 2011 at 4:37 PM, Chris Clearfield

> <chris.cl...@gmail.com <mailto:chris.cl...@gmail.com>>

> <mailto:nycresistormi...@googlegroups.com>.

> >>> To unsubscribe from this group, send email to
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> >>>
> >>
> >>
> >>
> >> --
> >>
> >> Michael Lowry
> >> Research Assistant
> >>
> >> NYU Minimally Invasive Surgery Lab
> >>
> >> 423 E 23rd Street, New York, NY 10010
> >>

> >> Office: (212) 686-7500 X6441 <tel:%28212%29%20686-7500%20X6441>
> >> Cell: (201) 787-8633 <tel:%28201%29%20787-8633>
> >>
> >> mt...@njit.edu <mailto:mt...@njit.edu>

> >>
> >>
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> >
> >
> >
> > --
> > Chris Clearfield
>
>
>
> --
> Chris Clearfield
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> Michael Lowry
> Research Assistant
>
> NYU Minimally Invasive Surgery Lab
>
> 423 E 23rd Street, New York, NY 10010
>
> Office: (212) 686-7500 X6441
> Cell: (201) 787-8633
>

> mt...@njit.edu <mailto:mt...@njit.edu>

>
>
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