Difference between revisions of "Raspberry Pi"

From Info Wiki
Jump to: navigation, search
(added info re fragile capacitor & power supplies)
 
(added ref to Ver 2 & B+ models)
 
(3 intermediate revisions by the same user not shown)
Line 1: Line 1:
 
A growing body of information is available at http://www.raspberrypi.org
 
A growing body of information is available at http://www.raspberrypi.org
   
Only a couple of '''critical''' issues, that are easily overlooked, are summarised below
+
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"
  +
  +
  +
[[Image:Raspberry_Pi_CD_Case.png]]
  +
  +
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 ==
 
== 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.
 
Power is supplied via the micro-USB connector at one end. The surface-mounted capacitor behind that connector is a known physical weak-point.
Line 22: Line 89:
 
#*1 A available to a single socket
 
#*1 A available to a single socket
   
[[User:Rpeters|Rpeters]]09:23, 8 September 2012 (EST)
+
[[User:Rpeters|Rpeters]]12:53, 26 January 2013 (EST)
 
[[Category:Technical Info]]
 
[[Category:Technical Info]]

Latest revision as of 14:48, 18 January 2015

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"


Raspberry Pi CD Case.png

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)