Raspberry Pi

A growing body of information is available at http://www.raspberrypi.org

Only a few critical issues, that are easily overlooked, are summarised below

Models

Most will purchase the model B, which has Ethernet and more USB ports

The second release of model B has 512 MB RAM in lieu 256 MB

• likely to increase the variety of OS that are usable
• earlier boards are not upgradeable, because all components are soldered in place

Case

The basic product is sold without a case. It does not fit in any "standard" blank case and has sockets on both sides as well as all four edges, making construction of a suitable case not a simple task.

Cases are now being sold on the Raspberry Pi site. Alternatively, third-party cases are also marketed

The two (only) chips on RPi can get quite hot in operation. Small, self-adhesive heatsinks are now available from:

http://geekroo.com/site/

Heat Load

Quick Start Guide from distributor RS Components recommends:

• "use in well-ventillated area"
• "should not be covered"

It's debatable whether or hot the majority of cases being sold meet the above criteria.

Alternatives to Cases

A DIY cover can be made usiing discarded CD media. The original concept was at

http://discpi.vkspartak.sk/

That "case":

• applies to the original (ver 1 - although not labelled as such) RPi
• does not anchor the RPi down and dimensions for accuately positioning the plastic supports are not provided. A variation, including critical dimensions is below

Ver 1 and model B+ have two and four mounting holes respectively.

• conventional plastic standoffs could be used in any "case"

Some construction factors to note, In either variant

• RPi have been produced on at least two production lines
  • precise dimensions of the board might vary
  • check prior to construction, preferably using plastic vernier calipers
  • adjust position of supports accordingly
• single plastic disks/CD media, although quite tough, are fairly flexible
  • two can be "laminated" together to form each of the top and base
  • the plastic in them is not tolerant of most solvents/glues - alternative is to place near the perimeter:
  • several small dots of hot-melt glue or
  • several strips of (non-foam) "double-sided" tape
• metal components of the case must be well insulated
• surprising force is required to insert/remove the SD Card & USB plugs, in particular. The supports must resist horizontal movement of the board
• the board is offset longitudinally towards the USB/RJ45 end, in order to:
  • facilitate insertion removal of USB/Ethernet plugs
  • prevent SD card overhanging case
• a minimium standoff of about 7 mm is required for board above lower CD.to facilitate insertion/removal of plugs
• if actual CD media are used (in lieu of plastic spacers from CD stacks) then the reflective sides must face inwards
  • top sides of media can be conductive aluminium
  • clear any drillled holes of flaked aluminium swarf
  • reflective surfaces aid monitoring of the RPi's five tell-tale LED
• drill CD media at slow speed
  • otherwise the plastic is inclined to melt and clog drlll bits
• on early production (at least) of the RPi model B, the Ethernet socket is not well anchored
  • desirable to adhere plastic spacers above it so the top CD holds it down
• a discarded case from a stack of 20/25 CD/DVD media can be used to protect the "CD-RPi" during transport
  • need to cut off the central spigot of the media case

Circuit Board

Power is supplied via the micro-USB connector at one end. The surface-mounted capacitor behind that connector is a known physical weak-point.

• do not grip the board by that capacitor
• preferably leave the micro-USB power cable permanently plugged in and power ON?OFF by either
  • powering the plug-pack/USB-hub ON?OFF or
  • disconnecting the other end of the power cable

Power Supply

1. A raspberry pi draws 0.7A (700 mA) of regulated 5V power, which is beyond the capacity of most:
   • USB sockets on a computer
   • mains-USB plug packs
2. Suitable power supplies include
   • mains-USB plug packs rated at 1A
     • preferably having a single USB socket only
   • USB-hubs capable to delivering 1 A to a single USB socket
     • "Zipp" brand from Big W does - but check before purchasing
3. although the use of a USB-hub as a power source is deprecated by the manufacturers, it has been used sucessfully by the developers at http://www.ipfire.org. Critical factors are:
   • regulated power to the hub
   • 1 A available to a single socket

Rpeters12:53, 26 January 2013 (EST)