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.
During peak current (when searching for satellites) I won't be writing any data to the SD Card.
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 was thinking that I could put the Mega328 to sleep until it starts to receive the NMEA data through the UART.
The arrival of serial data does not, normally, wake a sleeping Arduino.
Sleeping the Arduino, which uses very little power, while the GPS is sucking up power like there's no tomorrow seems a bit silly.
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.
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.
PaulS:
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.
The arrival of serial data does not, normally, wake a sleeping Arduino.
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.
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.
You are confusing a maximum safe current limit to the actual current consumption for the 328p chip which is more in the 25ma range when running at 5vdc @ 16Mhz, less if running at slower and at 3.3vdc. The rest of the current (up to 200ma) is what may or may be drawn from output pins wired to external components consuming the Vcc current.
uhhh....okay maybe not......I just put that part together in eagle and dang it is small. I'm pretty sure I won't be able to solder that. How are you supposed to use something that is in a package that is 1.5mm X 1.05mm? (6 PADS!!!) Am I reading that datasheet correctly?
jerseyguy1996:
How are you supposed to use something that is in a package that is 1.5mm X 1.05mm? (6 PADS!!!) Am I reading that datasheet correctly?
You aren't. These size devices are really only meant for automated manufacturing. I'm not even sure you could place such a part by hand, even if you had custom PCBs printed and a solder-paste stencil to match. I'm not saying it would be impossible - maybe with the proper microscope and a very steady hand...
