Computing stuff tied to the physical world

… and pies

In Hardware on Jun 25, 2012 at 00:01

This post follows up on yesterday’s first dive into the Raspberry Pi computer.

I switched to a beta of the next Debian release, called Wheezy. Full screen detect out of the box now:

DSC 3343

Those stripes are artifacts – that’s Moiré kicking in when using CCD pixels to take a picture of TFT LCD pixels.

The idea is to turn this thing into a permanent fixture on the back of this panel – right above my workbench:

DSC 3346

This is using a separate 5V and a 12V supply for now, but I’d like to explore a range of other options:

  • no keyboard or mouse normally attached
  • using a USB WiFi dongle instead of wired Ethernet
  • powered from a single 12V @ 2A DC power brick
  • add a step-down switching regulator to generate 5V
  • maybe: relays to control power to display and computer
  • a PIR motion sensor plus light sensor to detect presence?
  • a JeeNode USB, perhaps used as central node or as OOK relay
  • and maybe also a rechargeable 6V or 12V battery as UPS

The latter depends on whether this setup will become part of the permanent home automation system at JeeLabs.

As switcher I’ll use a no-name brand from eBay – it delivers 5V at over 1 A and draws about 8 mA without load:

DSC 3345

Lots of pesky little details need to be worked out, such as how to get a Sitecom WLA-1000 USB WiFi dongle working, how to set up what is essentially “kiosk mode”, and how to control the display backlight. I’d also like to hook up an RFM12B directly to the main board, to see how convenient this is and what can be done with it.

There’s a nice article at about setting up something quite similar. Long live the sharing culture!

Total system cost should be roughly €100..150, since I recovered the screen from an old Dell laptop.


  1. I got my Pi some time ago and as described in my Blog ( , it is used to gather the data from my JeeNodes in the house and send it to Pachube/Cosm.

    I switched to , because it has hardware accelerated floating point compiled in – the normal debian ARM uses software FP. I don’t know, how good the X11-Settings are there – I am running my RasPI “headless” – SSH is enough for me…

    I really look forward to connect an RF12B directly to the RasPI – that would “free” the currently used Arduino and the USB port. So please try this, write a driver for Linux for that and, as usual, share this with us ;-)

    BTW: The recycled Laptop-Display is nice – I just remembered, that I still have a dead laptop with hopefully working display somewhere…

  2. Re: wifi dongle, apart from the right firmware & driver, many of them need more than the ~100 mA the R-Pi’s output polyfuses F1,F2 allow. You can of course replace the fuses with a short :-). See also:

    • Thanks – yes, I may have bumped into that one. I have ordered another brand dongle, just to be sure. It’s a bit unfortunate that the Raspberry Pi has no wireless built-in (it seems to me like a far more convenient option than wired, in many cases).

  3. A lot of people feel that way, but the designers felt they had to sacrifice wifi to meet their cost goal while preserving the base feature set (including the size of the SDRAM). The R-Pi has been reported to work with Ralink 5370 devices, which are fairly cheap:

Comments are closed.