Raspberry PI Powered by AC,  Automobile Accessory or Rechargeable DC source

The eventual result of this instructable is, a portable (self powered) raspberry pi system to run field experiments. 

Part 1

Small inexpensive portable system that includes, Computer (RPI), Monitor with Audio speakers (Secondary screen from refurbished Auto DVD player $29 including the DVD player to be repurposed), wireless keyboard with touch-pad (FAVI or alike micro keyboard).All powered by my rechargable compressor/ 12 volt power source ($39 and I already had it for use with my pneumatic cannon). The compressor has another use filling tires when away from power but that was just an excuse to buy it. I also plan to have an AC supply make from a USB Hard DIsk programmer (12v and 5v 1.5A each convenient).

(new my UPS battery backup died, but the battery is still good I will make a pigtail to auto accessory adapter)

Yes I know you could use a Atrix Lapdock (I have one it was only $35 and use it for demos, but this is more fun and less fragile, if you have one you know). Besides it just looks like a laptop, and kind of takes away from the mad scientist image I am shooting for.

So Lets get going..  


Raspbery Pi and case (see my instructable) http://www.instructables.com/id/Raspberry-PI-case-with-built-in-surface-mount-for-/

uto DVD player secondary screen (mine was from Cow Boom for $29)

Keyboard Favi wireless micro keyboard 

Favi keyboard

12V Power Supply rechargeable: Home Depot Link

PC Hard drive power extender cable  male and female.

Sabernet hard drive programmer power supply.

USB car charger (make sure you can deliver at least 1 amp otherwise it is useless).

radio shack car lighter slitter (you will be cutting one off but so be it.)

12 volt connector for your dvd second screen ( I had one from some other device I had, junk drawer)

Micro USB connector, cut one of your cables but my suggestion is to buy one of the "charger connectors" from radio shack, the RPI needs current and the more you can deliver the better it will perform.

Optional  WIFI I use a AM150 it can run off the PI with no power issues (this is big).

Latest Raspbian Build ( I won't go into this part it is part of owning a PI).

Various connectors cable depending on your screen:
Stereo jack (from an old head set or a common connector from Radio Shack, I went for this they are cheap and easy to assemble).
I used intercom cable for power the stuff I have can is 24 guage more than I needed.
Composite video male to male. 
Usb Type A to plug into the charger. 

Wire strippers and snips.
Soldering Iron / solder (you can do all this without it but the cost of cables and connectors gets high)
Glue Gun / glue

I am an older engineer from the days when the ability to solder was taught in EE labs. Now here in the US we don't graduate as many EEs and almost all of those never touch any analog power circuits filters or antennas (about the only place you still solder). OK, I will get off the soap box.

NEW: Added video here to see if you are interested:

Step 1: Power Cable and AC to DC Power Scource

Cut your 4 conductor cable to the desired length (you can use three but separate grounds are better for current, I won't get into hole verses electron flow). Strip the sleeve off about 3 inches on one end and a little more on the other end. Strip all ends so that about 1/2 inch is exposed.  Take your hard drive extender cable and cut it in half (less if you want to dress it better), strip all the ends. Splice the pairs RED on the hard drive connector is 5 volts on mine ORANGE is 12 volts (try to make black or green your grounds for 12 and 5 volts). If you have heat shrink tubing you can use to cover your spice, if not use electrical tape. 

To make it easy to splice do not just twist them together (end to end), this make it bulky and forces an unnatural bend. Instead twist then beginning to end see the pictures. On the device side you have to solder your +5 and ground to your micro usb charging connector ohm it twice solder it once (spend some time here to get it right no sense in blowing up your PI). Do the same for your DVD screen power most are labeled with an orientation (ground is usually the outside.  

Now that you have the DVD screen wired use a glue gun to 1. keep the two power from shorting and 2. create some strain relief for when you disconnect. 

Again check your power connections all the way through, better safe than sorry. 

What are the capabilities of this?
<p>Nice project! You should check <a href="http://voltatek.com" rel="nofollow"> http://voltatek.com</a></p><p>for mini wifi adapters for raspberry pi and mini wireless keyboards and other stuff. They ship from Canada</p>
You could use a car rear-view backup monitor screen for a display. <br>A 3-12&quot; or 4-12&quot; monitor goes for $20 - $25 on eBay. These are standard <br>NTSC LED monitors that use an RCA connector cable for hookup directly to <br>the Pi's RCA video jack. <br>
The advantage of the one over the backup monitor many have used was: <br>It had speaker, with volume control, brightness control. <br>It was bigger than the backup monitor. <br>Even with using the second screen used for my project I still had a working mini DVD player (used it in blackouts). <br>Last and best it was $20 from Cowboom.
@Gelfling6 <br>Just one single MOSFET and a couple of resistors can be used as a level shifter. That's about as zero budget as it's gonna get. You probably have those components lying around. See this article: http://ics.nxp.com/support/documents/interface/pdf/an97055.pdf <br>As the article states, it even works for 2 way I2C protocol. I've used a surplus BS170 successfully with SPI protocol and general purpose datalines. Good luck!
And people said I was bonkers, hauling a 12V inverter with me to run a small desktop computer from the back of the car.. Well done! Yes, the RPi is small enough to make it portable! I had a few stumbling blocks getting mine up &amp; running, but pretty sure I've got it with the latest Raspbian release. Now, the hard part is working on talking out via the GPIO, to other things.. the 3.3V limitation, is what's killing me.. Already picked-up plenty of pointers and ideas for level-shifters, but on a zero budget, it's a pain. <br>
Cool Project! <br>Can you start xcmb from pi`s desktop or do you have a seperate sd card with linux for that? <br> <br>gr Mark
They are different projects for me, I use different cards. Raspbian if for experimentation, XMBC is for entertainment. I use one of my RPIs (yes I have 2) as a media server (Bluecop-Freecable, Hulu, Amazon Prime and in network streamer) the other goes back an forth depending on what I am doing.
Thats cool,i'm trying to start xcmb from pi's desktop so you dont have to switch the sd cards. Do you know if its possible to start xbmc from pi's desktop?
You could but it will take some work here is a site to help you. <br>http://www.raspbian.org/RaspbianXBMC <br> <br>If you don't want to do all that try this, the short way is to use this site it is exactly what you are looking for. <br> <br>http://michael.gorven.za.net/raspberrypi/xbmc <br> <br>Note XBMC does not go through Xorg therefore you cannot invoke it from the desktop you can only use the console command line or a startup script (you write it and decide what to do via keyboard). <br>http://michael.gorven.za.net/raspberrypi/xbmc <br> <br> <br>
Awesome! i will try it. <br> thanks for your help :)

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