Hackaday Links: Sunday, April 7th, 2013


Let’s wind down the weekend with some projects that didn’t quite warrant their own feature, but we think they’re still worth a look.

First up is a quick tip on cracking the lids on those hard to open jars of food. [Jason] says just grab about a foot of duct tape and the lid will come flying off. And while you’re searching for that roll of tape why not grab some foil tape to build a cooking oven. [Gabriel] built this solar oven by covering curved wedges of cardboard with foil tape and combining them to form a parabolic reflector.

Next we’ve got a trio of hacks that will come in useful in your home shop or at the local Hackerspace. Organization is key, and here’s a resistor storage system that uses #6 envelopes [via Reddit]. Also useful is the tip from [Felix] about using a tile saw to get clean cuts on your circuit boards. And if you’ve ever been plagued by a laser cutter job that doesn’t fully sever the material [Dan] wrote a guide on using a fence so that you can reposition the piece for another run.

Finally, we’re hoping we weren’t the only ones that didn’t realize the Raspberry Pi has an unpopulated footprint for a reset button. Now we’ve got to figure out if it’s okay to leave the PSU plugged in (based on it’s current consumption while the RPi is in power down) and hack together some sort of TV-based reset circuit for our RPi XBMC setup.


  1. Hirudinea says:

    Re: Duct tape to open jars. Too much work, just get a butter knife, hit the rim of the lid at a 45 degree angle with the back edge of the knife 3 or 4 times and it will come off no problem.

    • Nicolai says:

      Or even better. Buy a good lid opener tool.
      Like this one: http://world4.info/lid-opener-tool-vintage/

      • M4CGYV3R says:

        Or even better, twist it off by hand.

        I have met some seriously stubborn lids, but nothing that won’t open with a few good raps of the knuckles and elbow-torque.

        There has to be a jar opening contest somewhere. I want in.

        • Mental2k says:

          I suspect grip is the reason a lot of people have trouble with lids. That is to say the people I see having trouble opening things tend to use their fingertips (or somewhere around the first knuckle) to grasp the lid for opening. Personally I prefer to wrap my first (or middle) finger and thumb around the lid and twist it around that way. Then again it might all be in my head.

        • HomelyPoet says:

          I wouldst seek admittance to such a contest as well, M4CGYV3R.

          Though be cautious with the knuckle-rapping, as some jars will burst.

      • T4b says:

        We’ve got one which looks almost exactly like the one in this picture only the handle is white.
        Works quite nice, but one still needs to be careful if you don’t want to damage the lids.

  2. Lloyd Atkinson says:

    I still don’t know why the Raspberry Pi dosen’t have an actual power on/off button. Even if it’s just a slide switch.

    • Truth says:

      Extra hardware costs money and their goal was to fix the price point and then design the hardware to achieve that price. I’d prefer a RTC was added to keep time when bounced and not networked. It has a lot of compromises , most to achieve the price point, some are good some are bad.

      UNIX file systems used to not take kindly to being bounced, it is always better to shut them down them down cleanly. I always remember typing “sync”, “sleep 30″, “halt” on old SunOS servers to make sure they they would boot up again without needing an fsck and moving files into “lost+found”.

  3. Chris C. says:

    More jar opening:

    1) If the jar contains liquids, here’s an improvement to Hirudinea’s trick. Just turn it upside down and whack the bottom of the jar sharply with your hand a few times. If you’re familiar with the trick to bust out the bottom of a beer bottle, you’ll know why this works – and works well.

    2) If there’s sugary food on the jar/lid threads, rinse the lid under hot water, then use a towel to remove. The hot water softens the food. Sometimes it works in other situations, by causing thermal expansion of the lid which makes it looser.

  4. Gert says:

    Save yourself some time (especially if you don’t have a supply yet) with making those envelopes, and just buy a kit with see-through plastic baggies… Then buy more of what you need as needed (e.g. especially 10kohm).

  5. Ren says:

    Inre: Solar oven
    tl;dr^Hwatch (42 minutes!)

  6. dubloe7 says:

    There are laser engravers that don’t come with built in guides? How would you ever square anything?

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