Pi laptop in a box

[secretreeve]

So i'll be *hopefully* getting the model B on release and this is what i intend on doing with it.

taking a boring stock aluminium flight case



Then adding some aluminium sheet metal after cutting a hole out of the top peice that goes in the lid. This will house the 7" 12v monitor.



then add the bottom peice. The Pi, Pi's battery pack, monitors battery pack, usb hub and its battery will all be attatched to the bottom side of this sheet.



On the top a keyboard and usb touchpad will be mounted. and well thats pretty much it.

[secretreeve]

appologies for the massive space between everything, first time using this forums image stuff so getting used to it lol

[JeremyF]

Looks like a clever idea, but the case looks heavy.

[secretreeve]

actually its REALLY light weight. its basically 1mm aluminium sheet with a 2mm thick wood/cardboard type internal side to it so its really light weight but has some decent strength. all in it prolly weights at the moment 500g to 700g, estimated total weight completed is 1.5kg to 2kg

[JakeGrey]

I see I'm not the only person to think of this. I'm planning something similar, only with an old imitation-leather briefcase my landlady found in her attic.

The two biggest issues that have been dogging me since I thought it up are how to power both the R-Pi and the screen with only one cable and where to find a reasonably priced 7-inch monitor, but I think I've managed to rather elegantly solve both problems.

You see, a lot of portable LCD television sets not only have an HDMI input, but a USB port as well in order to view pictures and video files off a thumb drive.They also happen to be significantly cheaper than the in-car computing screens I was previously considering, probably on account of not having a touchscreen.

There are also USB cables available that can draw power from one device to another without exchanging data as well; they're normally used to charge mobile phones, and also helpfully include a mains plug with a USB socket should I wish to use the R-Pi through another screen or projector. The R-Pi can't possibly draw more power than something like an external hard drive or a smartphone with a dead battery, either.

[secretreeve]

well liz said that the Pi can run well of 4 AA batteries, although she didnt say how long it will run on them for its something i will be testing.

so im going to run my Pi of 4 AA batteries most likely, add a 6v NiMH battery for the usb hub and a 12v NiMh for the 7" monitor.

the screen i have chosen costs around £40 from ebay and has dual RCA inputs on the monitor, so while the Pi will only use the 1 it means i can use the monitor for a second device.

Anyway, lots of buy for it, screen, battery packs, charger, usb keyboard, usb hub, sticky back velcro to attatch everything to the metal sheet, microsd card adaptor and a couple of cables, mainly a hdmi > vga, normal hdmi cable and a vga > dvi adaptor (so it can be plugged into any larger modern TV)

in the mean time though i found a usb touchpad that im hoping will work on linux as a mouse similar to those of a laptop.

[JakeGrey]

My knowledge of electrical wiring is somewhat limited, so I was going to use the TV set's battery to power both. The models I've seen on offer claim around five hours, but that's presumably while using the digital antenna; the screen on its own might not be so bad.

And as for a keyboard and mouse, http://www.keyboardspecialists.co.uk has some compact all-in-one examples that look pretty good, even if most of their inventory costs more than many people spend on a whole PC.

[JeremyF]

Significantly cheaper than what JakeGrey found...

http://www.tigerdirect.com/app.....;CatId=533

[secretreeve]

if you dont have alot of electrical know how it will be alot safer and easier to run 2/3 battery packs, one for each of the devices, mostly because the monitors run from 12v for the better part and you dont want your Pi hooked up to a 12v source as it'll fry the Pi. you would need voltage reduction and current reduction. and one thing that stuck with me from school is that electricity is lazy and always takes the easy route. while it can be made to run from a single power pack it will be alot more complicated.

those keyboards are pretty good for what i've seen though.

[bredman]

It is much easier and more efficient if you can use a single battery pack, probably 12v. Use proper voltage regulators to convert from 12v to the voltage that you need for each device. See for example part 40378 from dx.com (I have not tested this on RPi yet).

By using voltage regulators, you can charge the battery while it is being used. Any voltage regulator for use in a car can easily tolerate the 14.4 volts which is used to charge a 12v battery.

Be very careful in your choice of battery. A lead-acid battery is a bit heavier but will tolerate any type of charging. NiMH or Li-ION batteries are VERY dangerous if you do not charge them the correct way and it can be difficult to charge them while they are being used.

Do not even think of running an RPi directly from 4 AA batteries. It will be impossible to get the correct voltage.

[secretreeve]

how bout some links to the various bits n peices needed to power the Pi on a battery pack?

cause everyone on here says you need this and need that but very few links are here and could to with them.

i mean if we wanted to take 1x 12volt battery to power the Pi and a 12v lcd what would be needed and how would it need to be assembled?

[grumpyoldgit]

The reality is that as no-one has a Pi in their hot sweaty palms, it hasn't been done yet. Plenty of advice and speculation but until the first poor sucker blows themselves up / Pi owner manages to do it, we will all have to wait in eager anticipation.

[JakeGrey]

A powered USB port in the back of a portable LCD television probably has better voltage regulation and other safety features than anything I could MacGuyver up in my spare time.

[secretreeve]

except the screen i've picked up doesnt have any usb ouputs on it so rules that option out sadly

[drgeoff]

JakeGrey said:


A powered USB port in the back of a portable LCD television probably has better voltage regulation and other safety features than anything I could MacGuyver up in my spare time.


Those USB ports often are only intended for flash drives.  You might or might not be lucky powering an RP from one.

[secretreeve]

out of interest, would it be better to use something like a 24v NiMh battery pack to power the screen, Pi AND usb hub all from one battery? obviously with the step down converters and current regulators in place.

or would that not increase battery run time and be utterly pointless?

[secretreeve]

okay so i figured out i need these bits:

voltage regulator (1 per device on the battery, so 3 in total)

adjustable amp regulators (again 1 per device, so 3 in total, the adjustable would allow for precise ampage to the devices)

and well thats all i got for now, i have little idea which resistors would be needed to hook up a monitor, usb hub and the Pi or any other components

that said i have no idea what will suffice for the voltage and amp regulators.

HELP PLEASE!

i know the monitor uses 12v but no idea how many amps

the usb hub, 5.5v @ 1amp (guessing the amps)

Pi 5.5v @ 1amp tops

the battery of choice is

Capacity:  3700mAh
Measured at 740mA (0.2C) discharge.
Max Discharge Current:  30,000mA (30 Amps!)
Max Charge Current:  3500mA
Internal Resistance:  <37mOhms when fully charged (<4mOhms per cell)

so which regulators would be needed to steady the voltage from the battery to each of the devices along with the amps?

if you can put up a basic schematic that would be amazingly helpful, i know its asking alot but with any luck im hoping this would help others out who are considering the laptop Pi idea.

[secretreeve]

okay i've asked for the above information else where so hopefully i will be able to start putting something together in a week or so for running a monitor, the pi and a powered usb hub off 1 12v battery with adjustable voltage and ampage outputs for each device ensuring safe delivery of power

[Jim Manley]

The R-Pi can accept 6 - 20 volts as input, although the production boards will be equipped with a micro-USB connector common to cell phone chargers.  The R-Pi only requires one watt which, at 5 volts, is 200 ma of current.  At least another 100 ma should be added for pass-through to a USB device on the Model A's single USB port (for a total of 300 ma), and up to another 500 ma should be added for the two USB ports on the Model B (i.e., 700 ma total).

[secretreeve]

thats some helpful information. very much appreciated.

im going to be doing some work on a breadboard for testing the psu and will eventually transfer it over to a prototype board and possibly make my own green pcb board for it. if it works well and within all the tolerance limits then i'll probably sell them depending on how many are wanted. but i will also be putting up any schematics for the psu once its actually done

[Lynbarn]

Jim Manley said:


The R-Pi can accept 6 – 20 volts as input, although the production boards will be equipped with a micro-USB connector common to cell phone chargers.  The R-Pi only requires one watt which, at 5 volts, is 200 ma of current.  At least another 100 ma should be added for pass-through to a USB device on the Model A's single USB port (for a total of 300 ma), and up to another 500 ma should be added for the two USB ports on the Model B (i.e., 700 ma total).


Warning! The BETA boards can accept 6-20V – I'm not sure, but I think the production boards (will) accept only 5V through the micro-USB power socket. DON'T try 20V through that! (IIRC it can also be powered through the GPIO too, but again. only at 5V).

[turbomonkey]

For the Rasberry Pi board running at 5v you can use a voltage regulator such as the LM7805, this will give a constant voltage output at 5v, this will deliver up to 1 amp which should be plenty for your board, does it say if the current rating is R.M.S?

You would connect the regulator with positive to positive, ground to ground and the output pin will be 5v

You can use a resistor to resist the current flowing through the circuit as well as placing a smoothing capacitor in parallel with your power supply to reduce fluctuations.

Similarly you can regulate a 12v supply through a regulator as above (or you can use a zener diode http://www.reuk.co.uk/What-is-.....-Diode.htm) , although a screen might pull a bit more than 1 amp so look for one with the right current rating. (depending on your source you might not need to regulate the supply)

Have you had a look at laptop batteries? You can seem to get ones with a damn good capacity for not that much money, the more mAh the better.

You might also want to consider adding a cooling fan if your putting the board in an enclosed box, you can use either your 12v or 5v supply.

Hope this helps your project.

[curiousengr]

you can get 12v to 5v DC to DC converters from ebay -small cheap and can power up to 3A. The amps will take care of themselves as long as the voltage is maintained at a regulated 5volt so long as the power in is sufficient to supply the amps there no problem.if you try to supply more than 5volts plus a little tolerance (5.2v) the RaspPi will start to fry and you will have cooked(and burned) your Pi.

burnt Pi is known as Bricked (as much use as).lots of in car devices and ITX motherboards use 12voly supplies with internal 12 to 5v converters.

I expect to mount my RaspPi on a prototyping board with satelite boards to mount 5volt power supply -external power is 12volts from a laptop type AC adaptor.

Now that I have seen the photo of the underside I know I will be remove the connectors and run ribbon cable from the Pi to fit the various connectors on the edge of my external box leaving room for port powered hub from one usb ,internal USB Stick in the other port,12v to 5v power supply.

hope this gives you something to think about

[liz]

Don't know if you guys have seen it already, but this project idea was called out in TechRepublic today as one of the ten coolest uses for a Raspberry Pi. Well done!

[secretreeve]

holy!!

thats the last thing i ever expected lol. sadly this projects shelfed until the backlogs cleared and i can order one it lol