mokargas
Posts: 5
Joined: Sun Jun 23, 2013 6:08 am

Newbie with first project, need a little help!

Sun Jun 23, 2013 6:19 am

Hello there everyone.

Complete noob here! I've bought my first pi, set it up with Raspbian, ran it headless and installed a node.js server on it to send data to a remote server.

My idea is to have a Pi, connected to a long-life battery (No idea which one, with say a days charge), with GPS and 3G functionality. It will be mobile (let's say on a person, donkey or landshark) and send GPS co-ordinates to the remote server (which plots them on a Google Map). Eventually I envisage a few buttons and LEDs and the like on the device too.

Now I'm a software guy, not hardware, so this is my first foray into electronics prototyping! I don't know what GPS to use or what 3G system to use (I have seen Arduino "shields" and USB sticks for this?).

My question is really 'where to start?', should I learn soldering and electronics before beginning, or is it not necessary?

cae2100
Posts: 143
Joined: Tue Jan 08, 2013 10:35 am
Contact: Website

Re: Newbie with first project, need a little help!

Tue Jun 25, 2013 5:03 am

there are a few small usb gps modules that Ive seen used with the raspberry pi, and same with 3g dongles, just plug them in and search through the forums here, and you should find everything you would need to know to get updated. There is python code and such to upload sensor readings and such from the rpi to google spreadsheet, but Im certain it can be changed to another type of remote server.

Just try searching through the forums here, and if you cant find what you're looking for, just google "raspberry pi projects" on google and you'll find a ton of stuff like your talking about. As for battery life, idk any that would run for a full 24 hours with the rpi B version, but maybe with the A version and the one self powered hub that's on the forums, the SB hub or something like that.
If it isnt smoking and blown into pieces, it's not pushed far enough yet. :P
http://cae2100.wordpress.com

PiGraham
Posts: 3566
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Newbie with first project, need a little help!

Tue Jun 25, 2013 6:26 am

Just a reality check. Are you doing this because it's fun / educational, or because you need to GPS track something? If all you need is to track something with GPS / GSM be aware there are devices around that do just that for about $40. Google "GPS tracker". There's nothing wrong with "reinventing the wheel" if you want to know how to make wheels.

There are lots of modules out there that you can use in your custom project.

Search "raspberry gps tracker"

A couple of examples of kit:
http://www.sainsmart.com/arduino-compat ... tml?cat=23

http://learn.adafruit.com/adafruit-ulti ... troduction

https://www.sparkfun.com/products/10138
https://www.sparkfun.com/products/10138

mikey11
Posts: 354
Joined: Tue Jun 25, 2013 6:18 am
Location: canada
Contact: Website

Re: Newbie with first project, need a little help!

Tue Jun 25, 2013 6:55 am

what would it take to get a days charge?

I am relatively new to this myself, so if someone knows better, chime in.

The rpi has been widely quoted as using ~700ma

I have a 9900mAh battery, so do the math 9900/700 = ~14h

of course this assumes I can deplete the battery to 0% charge, which is somewhat unlikely, so lets say I can get 10h out of this battery.

Now if you add other devices like a GPS and 3G networking, your power consumption has just been driven up dramatically, so that 10h value probably drops to about 6h (just a guess, but look at the power consumption of these devices and add them to the 700mA of the rpi, and do the arithmetic)

I would hazard a guess that to get one day out of what you are looking at, you would want a 4Ah battery system. The easiest thing to do would probably be to find a 12v battery and then a voltage regulator to bring you down to 5v. you would likely want to have a separate USB hub from the rpi it self (ie, power the 3G and GPS from the hub, but have data running to the rpi)

I looked up laptop batteries on ebay, and it looks like you could find one for about $50
ex:
http://www.amazon.com/IBM-laptop-batter ... B0007UVYJO

This would be convenient, because often these batteries have charge regulators built in so you won't screw it up while charging, nor will you have to build your own charging control electronics.

For your reference, the 9900mAh unit I am using came from thinkgeek

http://www.thinkgeek.com/product/eb7b/?srp=3

I find it convenient, because it will run my rpi, but also give me a great backup supply for my tablet (galaxy tab)

mokargas
Posts: 5
Joined: Sun Jun 23, 2013 6:08 am

Re: Newbie with first project, need a little help!

Wed Jun 26, 2013 2:41 am

Thanks for your help guys.The project isn't really personal as much as I have a goal.

Here's what I bought after reading your materials and searching these frankly incredible forums:

- Yoobao 'Long March' Power Bank (11200 mAH)
- Huawei e220 USB Broadband/3G dongle
- Globalsat USB BU-353 GPS module

I've set-up the GPS and it receives co-ordinates perfectly. I don't have the 3G dongle yet, so I'm just using WIFI, but I'm able to send the co-ordinates via a node.js server to a webpage and plot locations on a Google map already. (I originally coded up this functionality, then found a better solution using a database here https://github.com/Adrianod/Open-GPS-tracker if anyone is interested)

So hopefully when the 3G comes through it will just be a matter of hooking it up and removing my Wifi dongle.

The battery pack provides oodles of power. My only issue with it, is that I can't run the Pi and charge the battery at the same time. Not sure on how to fix that, if indeed it's possible to fix it.

Thank you all once again for your help. I'll post up some images of my final setup when it is complete. I'm astonished what can be done with the Pi in less than a week.

PiGraham
Posts: 3566
Joined: Fri Jun 07, 2013 12:37 pm
Location: Waterlooville

Re: Newbie with first project, need a little help!

Wed Jun 26, 2013 6:04 am

To estimate battery life calculate the battery energy in Watt hours rather than the current, and the consumption in Watts.

A RasPi drawing a current of 700mA from a 5V supply is consuming power = 700 x 5 = 3500 mW.

We have a problem with a specification of 11,200mAH for a battery pack. To calculate the energy capacity we need a voltage and its probably the voltage of the cells inside the pack, not the voltage the pack produces. Li-Po cells are nominally 3.7V. Most RC batteries give the voltage - 3.7, 7.4 or 11.1V for 1, 2 or 3 cells.

Worst case you have one cell, 3.7V, which mean a capacity of:
3.7 x 11,200 = 41,440mAH.

The 3,500mW Pi should run for 41,440/ 3,500 = 11.8 H.

You are not likely to get that life in practice. I bought a battery pack described as 11,000mAH and it has much less capacity than the calculation would suggest. I think some suppliers are a bit creative with the specs. My pack was about 3,500mAH 3.7V.

Another thing to consider is that you need some sort of converter to connect a Li-Po to a RasPi (possibly built into the battery pack) and that will take some energy so you will get 10 to 20% less than V x A x H suggests.

sukotruco
Posts: 1
Joined: Wed Oct 01, 2014 1:36 pm

Re: Newbie with first project, need a little help!

Wed Oct 01, 2014 5:18 pm

Hi.

I´, very interesting in your project. I have the same Hardware but im not able to send the co-ordenates.
Im really new in Raspberry but i would like to work in that.
Could you help me with this procjet?

I check Open-GPS-tracker but i dont understand the node.js system.

Thanks a lot

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