On Wed, Dec 10, 2008 at 10:50:28AM -0800, Tyler Booth wrote: > Hate to rain on the wood parade, but aside from the heat insulation > issue, wood also has the tendency to > build up and store static electricity (I don't think I need to explain > why that's a bad thing). Also, considering > the time it would take to manufacture a single case it would add > considerable cost to the finished product over > the cheap aluminum cases that are pre-made for the board. > > While I agree that it would look WAY better than a cheap aluminum box, > I don't think it's practical.
Dry wood out of the kiln has high resistance, about 10^16 ohm-m, but is nothing like as high as plastic or glass. The charge holding time for a chunk of fresh dry wood is approximated by the dielectric constant times the resistivity, and is about 1000 seconds. Moist wood, on the other hand, is VERY conductive, about 10^3 ohm-m for saturated wood. It does not take much exposure to normal air to make wood moist enough to rapidly dissipate a charge. My worry was not static build up, but that moist wood can short out signals. Many PTP nodes are either outdoors or in restaurants with a lot of water vapor. Still, While those resistivities might drain some parasitic power off the ALIX board in places where they touched, it would not noticably affect signalling. The plastic sheet on the bottom of the Netgate ALIX box IS highly resistive. It will build and hold static charges for a long time. However, like all surfaces it will develop a thin dirty film over time, and that is what bleeds off the charge. That is a good thing, because they don't put the plastic sheet down very well; mine has bubbles in it, and on some boxes the bubbles may be high enough to touch the board. Ah well, puncture them with a pin and smooth them out. The plastic is there to keep stray bits of debris from shorting the underside of the board to the anodized metal case. Again, my main objection to the Netgate boxes (and I have one in front of me) is that the boxes are too tight, such that a complete disassembly is needed to get at the CF, and there is no way to anchor cables to the box. The homebrew box does not need to be as elaborate as routed wood. Rather than routing channels in wood, a large metal box ( perhaps a cooking pan) would also offer enough room to get at the flash. The box could be bolted to a wall. If the boxes have enough "lip", the covers could still be held on with velcro. Rather than mounting cables in channels, they could be tied down with zip ties to adhesive anchors inside the box. You could still make something nice looking, though perhaps not as nice as a slab of polished wood. Perhaps Rick can suggest some appropriately sized, inexpensive metal boxes that are large enough, and flat. Keith -- Keith Lofstrom [EMAIL PROTECTED] Voice (503)-520-1993 KLIC --- Keith Lofstrom Integrated Circuits --- "Your Ideas in Silicon" Design Contracting in Bipolar and CMOS - Analog, Digital, and Scan ICs --~--~---------~--~----~------------~-------~--~----~ The Personal Telco Project - http://www.personaltelco.net/ Donate to PTP: http://www.personaltelco.net/donate Archives: http://news.gmane.org/gmane.network.wireless.portland.general/ Etiquette: http://www.personaltelco.net/index.cgi/MailingListEtiquette List information: http://lists.personaltelco.net To post to this group, send email to [email protected] To unsubscribe from this group, send email to [EMAIL PROTECTED] -~----------~----~----~----~------~----~------~--~---
