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181  Using Arduino / Project Guidance / Re: Sizing a voltage regulator for an application? on: December 16, 2012, 07:34:32 pm
Really? How will you control this? There isn't, typically, a "search for satellites" command that you send to the GPS. It searches for them when it feels the need, and it isn't going to tell you when it feels the need.

I read somewhere that 4 satellites are needed to get an accurate location.  I mistakenly thought that once it had 4 satellites (which I can read from the NMEA data that is being spit out), that it would come out of "search" mode.

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The arrival of serial data does not, normally, wake a sleeping Arduino.

I was going to use this tutorial: http://rubenlaguna.com/wp/2008/10/15/arduino-sleep-mode-waking-up-when-receiving-data-on-the-usart/

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Sleeping the Arduino, which uses very little power, while the GPS is sucking up power like there's no tomorrow seems a bit silly.

Probably right......I was thinking about battery life and trying to maximize it.

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The 329-based Arduinos are typically 5.0V devices, unless you clock them at half speed - not a beginner project. Is the GPS a 3.3V device or a 5V device? Most are 5V devices.

I was going to use an mega328 with an arduino pro (8 mhz) boot loader.  The GPS and SD card both run on 3.3v so I figured it would just be easier to run the mega328 at 3.3 volts as well rather than level shifting everything.  I have a few other threads that I started to work through the issues associated with running an arduino at 3.3 volts.  I'm putting together the schematic in Eagle now and am hoping to post it on here before I send the board out to be made.
182  Using Arduino / Project Guidance / Sizing a voltage regulator for an application? on: December 16, 2012, 05:55:37 pm
I'm sure this will sound like a stupid question but I am wondering how much of a current buffer I would need to power the following devices? 

A2035 GPS Module - Peak Current = 49 mA
Mega328 - Maximum Current VCC -> GND = 200 mA
SD Card - ??? but I have read anywhere from 50 - 200 mA during a write operation
1 LED - 20mA

The program shouldn't ever have all devices operating at full power together.  Basically the GPS Module will be in full power tracking mode most of the time which the datasheet says draws 24 mA.  During peak current (when searching for satellites) I won't be writing any data to the SD Card.  I was thinking that I could put the Mega328 to sleep until it starts to receive the NMEA data through the UART.  Once it receives valid NMEA data it will write the lat and long position and time data to the SD Card.  I was hoping to run the whole thing off of a 3.7V LiPo battery and this 3.3v switching regulator which can handle up to 300 mA.

http://www.mouser.com/ProductDetail/Texas-Instruments/TPS62203DBVT/?qs=sGAEpiMZZMvAX9OfPh%252b2NdYypUYwsctEc%252bUiVMFRnng%3d
183  Using Arduino / Project Guidance / Re: How to solder an sd card connector to a pcb? on: December 16, 2012, 12:32:41 pm
Thanks everyone for all of the great suggestions!  And thanks to Duckie58 for the detailed explanation!
184  Using Arduino / Project Guidance / Re: Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 15, 2012, 11:09:32 pm

It's in the boards.txt file. In the IDE, as long as you pick one of the 8MHz boards when burning the bootloader and then also the same one when uploading a sketch, you shouldn't have to set anything.

Awesome!  Can't wait to try it out!
185  Using Arduino / Project Guidance / Re: How to solder an sd card connector to a pcb? on: December 15, 2012, 09:26:11 pm
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I reguested a sample from 3M and I will probably print the part out on paper and see if everything lines up before placing it on a board. 
Be careful how you do that. Plotting the part would be accurate. Printing it may not result in a 1/1 scale.

I'll have to print a known part next to it, something in a dip package, to verify that the scale is correct.
186  Using Arduino / Project Guidance / Re: How to solder an sd card connector to a pcb? on: December 15, 2012, 08:58:32 pm
Thanks everyone for the suggestions.  I actually found these on Mouser that have the tabs on the back which should be a lot easier to solder:

http://multimedia.3m.com/mws/mediawebserver?mwsId=66666UuZjcFSLXTtmXftMXMXEVuQEcuZgVs6EVs6E666666--

I've been making a part for it in eagle and I think I have all of the spacing of the pads worked out.  I reguested a sample from 3M and I will probably print the part out on paper and see if everything lines up before placing it on a board. 

187  Using Arduino / Project Guidance / Re: Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 15, 2012, 08:32:43 pm
FYI, uploading to an 8MHz ATmega328P works fine for me, using an Arduino Uno with an ATmega8u2 and the ATmega328P removed. The target chip on a breadboard has an 8MHz version of Optiboot, using an upload speed of 57600, and was powered by 5V from the Uno.

How do I set the upload speed to 57600 or is that all handled by the boot loader?
188  Using Arduino / Project Guidance / How to solder an sd card connector to a pcb? on: December 15, 2012, 02:25:09 pm
I requested this sample from Molex:



IMAG0766 by jg1996business, on Flickr


IMAG0767 by jg1996business, on Flickr

the datasheet is here:

http://www.molex.com/pdm_docs/sd/5035000991_sd.pdf

My question is, how do you solder those little tabs to your board?
189  Using Arduino / Project Guidance / Re: Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 15, 2012, 02:19:09 pm
Excellent!  and thank you!  So my steps will be:

1.  Upload the ArduinoISP sketch onto an Arduino Uno following these instructions http://arduino.cc/en/Tutorial/ArduinoISP
2.  Connect the Arduino Uno to my new mega328 as shown in the bottom images of the above link
3.  In the arduino dev environment go to tools-->programmer and set it to "Arduino as ISP"
4.  In the arduino dev environment go to tools-->board and set it to "Arduino Pro or Pro Mini (3.3V, 8 MHZ) w Atmega 328
5.  In the arduino dev environment go to tools-->Burn Bootloader

So now I should have a mega 328 that I can run off of 3.3V reliably but that I could still program with 5 volts via the arduino uno with its mega328 removed.  Is this correct?  Will the Atmega16U2 on the Uno have any problem communicating and uploading sketches to a mega328 running an 8MHZ boot loader?
190  Using Arduino / Project Guidance / Re: Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 15, 2012, 08:42:05 am
You could also just put it on the breadboard and connect the ground, reset, rx and tx to the arduino board that way you dont have to keep putting the chip in and out of the breadbard and arduino.

Also if you are doing anything time related you are still going to want to use a crystal and you'll need a bootloader meant for external 8mhz. If no time, then nevermind.

Is it safe to assume that anything involving the UART would be considered "time related"?  I was planning on using an 8MHZ external crystal for timing.  Is it a completely different bootloader that is needed or can I just modify the setting of the fuse bits in the boards.txt file in the hardware folder?  Couldn't I just compile the program as if I am using an arduino pro running at 3.3V and 8 MHZ and then program it through an old arduino board that still uses the FTDI chip (if using the FTDI chip versus the Atmega16U2 on the Uno even matters)?  I really don't understand how all of these parts on the arduino talk to each other. 
191  Using Arduino / Project Guidance / Re: Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 14, 2012, 10:56:40 pm
Thanks.....I will give it a try!
192  Using Arduino / Project Guidance / Re: 3.3v switching regulator on: December 14, 2012, 10:47:57 pm
Well sure I could buy an off the shelf product like a gps watch but that isn't any fun smiley-wink
193  Using Arduino / Project Guidance / Arduino Uno to program Mega328 with 8MHZ bootloader on breadboard? on: December 14, 2012, 10:43:29 pm
I want to run a mega328 at 3.3volts so I was looking at this tutorial
http://arduino.cc/en/Tutorial/ArduinoToBreadboard
and this tutorial
http://arduino.cc/en/Tutorial/ArduinoISP
to make it happen.  If I can get the bootloader onto the breadboarded mega328, will I be able to use an arduino uno (with the uC removed) to program the breadboarded mega328?
194  Using Arduino / Project Guidance / Re: 3.3v switching regulator on: December 14, 2012, 08:42:22 pm
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Is there a way to predict how long a battery with a certain capacity will last if I know the current draw of each device that it will be powering?

A one amp hour battery capacity (1000mAH) will power a one amp load for one hour, a 100ma load for 10 hours, a 10ma current load for 100 hours. I think you see a math thing at work in there somewhere?  smiley-wink

Lefty

Yes but isn't the voltage slowly falling over that 1 hour period (in the case of a 1000 mAH battery powering a 1 amp load)?  Wouldn't the voltage fall to a level that is un-useable before the hour is up?  Or does the battery capacity suggest an amount of power that can be delivered before the voltage starts to sag?
195  Using Arduino / Project Guidance / Re: 3.3v switching regulator on: December 14, 2012, 08:27:31 pm
I didn't realize that coin cells were so limited.  I'm glad I asked this now.  I originally had suggested that my wife use a running tracker app that she can get for her android phone but she doesn't want to have to carry the phone on a run because it is too big.  What I plan to make for her will be a lightweight box that is slightly bigger than an arduino nano that she can wear on a lanyard around her neck.  I think a battery such as the ones that come in those tiny remote controlled helicopters may be appropriate.  Is there a way to predict how long a battery with a certain capacity will last if I know the current draw of each device that it will be powering?
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