Making model rocket motor igniters

[Stephan Jones] has an easy method for making your own model rocket engine igniter. The solid state motors used in this hobby consume one igniter with each electrically triggered launch. Whether you’re making your own motors or not, this construction technique should prohibit you from every buying an igniter again. The process involves bending some nichrome wire around a paper clip, adding some structural support to the leads using masking tape, and insulating the business end with a quick dip in paint.

Now would be a good time to send us your launchpad hacks. All we’ve seen so far is a launchpad for water rockets.

[via Make]

Paper touchpad

If you don’t mind getting your fingers a little dirty you can replace your mouse with a piece of paper. [Dr. West] made this touchpad himself, which measures signals at the corners of the paper using four voltage dividers. The paper has been completely covered with graphite from a pencil (which we see in hacks from time to time), making it conductive. The user wears an anti-static strap that grounds their hand, allowing an Arduino to calculate contact points on two axes when a finger completes the circuit. See this controlling a cursor in the video after the break.

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How to weigh a bee hive

Did you know weighing bee hives was even necessary? Of course it is. Monitoring hive weight can tell a beekeeper a lot about the size of the swarm, their harvesting habits, and the yield they are producing.

We had to cover this hack because it’s a fine piece of engineering. [Trearick] designed a bee hive scale that lifts one side of the hive to calculate weight. Using easy to find metal brackets, a hinge, a pulley, and some plywood he built a prying device. The three teeth slip in between the hive and its base and can be separated by squeezing together the plywood handles on the opposite side. This lifts one end of the hive, measuring the force needed to do so using a luggage scale. The readout should be roughly 1/2 the total hive weight. This measurement takes seconds to complete, uses a bulb level on the scale to help ensure consistency, and creates little or no disturbance to our flying friends.

It’s nice to see a Hymenoptera hack that helps in giving bees a healthy place to live, instead of killing wasps.

DTG: improved printing on T-shirts

[Jeff German] improved upon his DIY direct to garment printer an ended up with a machine he thinks is equivalent to anything you can buy commercially. We last looked in on this project in June but much has been done since then. Most notably, there are build instructions available (requires login). [Jeff's] printer is based around an Epson R1900 plus the base that holds and feed a garment. Take a look after the break to see it printing full color designs in high resolution. From the YouTube description it sounds like he wants to go into production with this. Kudos to him for also sharing the build techniques.

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Jeri makes flexible EL displays

A failed chemistry experiment led [Jeri Ellsworth] to discover a flexible substrate for electroluminescent displays. We’re familiar with EL displays on the back of a glass panel like you would find in an audio receiver, but after making a mesh from aluminum foil [Jeri] looked at using the porous metal to host phosphors. She starts by cleaning foil and using a vinyl sticker to resist etching portions of the aluminum. It then goes into a bath of boric acid, electrified with the foil as the anode. As the foil etches she tests the progress by shining a laser through the foil. After this the phosphors are applied to the back surface of the foil, covered in a dielectric, and topped off with a conductive ink that will carry the AC necessary to excite the phosphors. This is layering materials in reverse compared to her EL PCB experiments. See [Jeri] explain this herself in the clip after the break.

You can see above that this produces a pretty well-defined display area. It reminds us of that color changing paint display. We think it would be worth a try to build a few 7-segment displays using this method.

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