Hackaday Links: March 29, 2015

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Every once in a while, the Hackaday Overlords have a Hardware Developers Didactic Galactic in San Francisco. Last week was #06 featuring [Mike Estee] from Othermill and Hackaday writer [Joshua Vasquez] talking about synthesizing an SPI slave in an FPGA. Video here.

It’s no secret that [Fran] is building a DSKY – the part of the Apollo guidance computer that was on-screen in Apollo 13. It’s time for a project update, and here’s where she stands: if anyone has a source of JAN-spec Teledyne 420 or 422-series magnetic latching relays (they’re in a TO-5 package), contact [Fran]. The backplane connector has been identified; it’s a Teradyne I/O 100 series connector with a 120mil spacing. Contact [Fran] if you know where to get them.

Let’s say you want a carbon fiber quadcopter frame. What’s the most reasonable thing you can do? 3D print a CNC machine, obviously. That’s a 200mm FPV racer cut from 1mm and 3mm carbon fiber sheets, but the real story here is the CNC machine. It’s a PortalCyclone, and even the cable chains are 3D printed.

What does an AMOLED display look like up close? Pretty cool, actually. That’s 20x magnification, and it’s not a Bayer filter. Can anyone fill us in on the reason for that?

Laser cutters are tricky if you want to do grayscale or half tones. [oni305] made an Inkscape extension to generate better GCode for engraving with a laser cutter.

19″ racks have no dimensions that are actually 19″. Also 2x4s aren’t 2 inches by four inches. Somehow, a 2×4 server rack works.

14 thoughts on “Hackaday Links: March 29, 2015

  1. Why would an AMOLED have a Bayer filter? It generates colored light already, no need to filter anything. Red subpixels are so much bigger because they are less efficient and actually need to produce more light to be seen as equally bright as blue and green.

    1. You have to filter out which part of the backlight’s spectrum you want to show in a given area. So you can have colors. Different colors on different places on a smartphone screen. It’s just an odd arrangement of the pixels that’s the issue, rather than the common Bayer arrangement, it’s similar to Pentile RGBG

  2. “Somehow, a 2×4 server rack works.”

    A doormat works also, when all you’re doing is putting two mid-towers in/on it.

    Good luck using a wood “rack” when you’re trying to mount any decent 1U or larger piece of hardware that weights 20+ kilo’s – most likely you’ll split the wood and spill your precious server onto the floor. Plus you’ll have to use nuts & bolts since there’s no way to make wood hold threads securely enough just to use a bolt.

    Wire bread racks are by far the better solution for small stacks or home systems (you can even build them from your magic 2×4’s and generic wire shelf units – just remember to take the rubber feet off the bottom of whatever you’re putting on the shelf so that it can slide in and out without chatter).

      1. I think you grossly underestimate the grain strength of cheap pine 2x4s. But yeah, if you drill in at an angle into the center of the board you’ll probably be OK.

        Of course, even cheap pine 2x4s are overhill when you don’t even have any rack gear to mount in the first place…

        1. Did you mean overestimate? I’ve been using cheap pine for a lot of things for a long time, handle it right and it won’t let you down. For f*ck’s sake, houses and buildings are often built out of the same stuff.

      2. for the wood, no that isn’t a problem. For the small mount of the wood interacting with the 4 1/4-20 screws at the front only (some gear doesn’t have rear mounting points or isn’t full depth) I’d worry about the 10kg per side on screws with little separation. That lack of space between the screws mean they could (emphasis on could) sheer the grain between them and weaken the wood, causing more weight on one side, causing the screws to sheer . . .

        Personally, I recommend college surplus auctions and thrift stores. I got two 3 foot tall rolling racks with lockable front and back for $50. One will hold networking gear once I move, the other is the geekiest kitchen island.

    1. Mounting something that heavy it would be awkward, but should have no problem structurally if you’re using 2″ or longer wood or drywall screws; and if you’re splitting the heck out of a 2×4 you’re doing it wrong or you really got the crappiest lumber possible. Bolts would indeed be silly, you may as well just put rack rails on your 2x4s at that point.

      I like the bread rack idea, thought, I’ve also used cast off oven racks for shelving.

  3. You can build a server rack out of 2×4, but I would recommend 4 rails, and a frame at the bottom & top. put casters on the bottom, with the UPS on the bottom for stability. I built one out of square aluminum wire molding, the kind you see going from the ceiling down to POS lanes. I had a UPS on the bottom, and an IBM Bladecenter on top of that. The 1U hps slid on the HP rails, since I built it to accommodate those. With 4 casters on the bottom.held together with self tapping sheet metal screws. I’d post pics, but soon got a real one & disassembled it because I needed the screws for something else in a pinch.

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