Piezoelectric materials are about as close to magic as you can get. They turn physical pressure into electricity and can even turn electricity into physical pressure – an amazing sort of bidirectional converter for mechanical and electrical energies. Perhaps even more amazing is the fact that you can easily ‘grow’ your own piezoelectric crystals overnight using just a couple of common ingredients – awesome.

Ever since I made my first contact microphone, I’ve been amazed by piezos and their unique abilities. I was more than psyched to learn I could make my own piezoelectric crystals after finding recipes online. Now I just need to figure out how I’ll put these little guys to good use … feel free to leave any ideas/suggestions in the comments below!

What does the top edge of say, your utility closet door look like? I’m betting that you’ve probably never seen it, even if you’ve lived in your home for awhile. And although there’s not a lot of room to hide stuff in there, well, if you’re like me, the stuff you want to hide is usually on the smaller side. Not many people think of the space inside the door as a hiding spot, but it’s right there in easy reaching distance when you need to get to it. And it’s devious enough that, yes, I think this trick will still be effective even after we blog it all over the tubes.

In true spirit, Make: Live is very much a DIY production. Instead of tripods, we use zip ties to mount webcams to chairs and we jury rig an old monitor to act as our prompter. Along those lines, I decided to create an on air light to indicate when we’re broadcasting. While I could have just wired a switch to a light fixture, I wanted to take the idea a step further. Using Ustream’s API, I set up our on air light to turn on automatically when we start broadcasting. This project was just for fun, but learning how to use the XBee Internet Gateway to get the Arduino online wirelessly will come in very handy for future projects.

Most of my networked projects have used an Arduino with an Ethernet Shield. For this one, I tried the XBee Internet Gateway, which is free ConnectPort software that allows XBee wireless radios to retrieve web pages. This allowed us to hang the light wherever we wanted without the need to run an Ethernet cable to it. Having an XBee Internet Gateway in my home also means that I can easily add wireless sensors and other internet-connected projects without filling up my router’s Ethernet ports.

This project serves as a good template for any kind of wireless notifier; it’s not just for Ustream. You could customize the project to indicate when your significant other is online, when you receive a new @ reply on twitter, or if rain is expected today. The Arduino and XBee Internet Gateway make a great pair for many internet-connected projects. To learn more about XBee mesh networks and the XBee Internet Gateway, Robert Faludi’s book, Building Wireless Sensor Networks is a great resource.

Check out the full project write-up over on Make: Projects:

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Many an experimenter, hacker, tinkerer, & maker have heeded the call of the mighty matrix – and it’s no mystery why. A small army of LEDs elegantly wired in grid formation would be difficult for anyone with an appreciation for electronics hardware to pass up – even after considering the sometimes daunting wiring job that stands as prerequisite to entry.

Needless to say, I had a lot of fun working with LED matrices for this installment of the Circuit Skills series. Many folks have published code for their matrix projects and it was great to be able to try some of them out. Breadboarding a two-color matrix did end up being a pretty tedious task – interested experimentors can pick up a one-color matrix kit from Jameco which should prove much easier to work with.

Oh, and I’ll be posting some of the adapted code used for this project, once I have a few kinks worked out – stay tuned.

Movie theater and other high quality screens are often surfaced with tiny glass beads to provide high “screen gain,” which is a measure of the screen’s reflectivity versus a reference surface. It occurred to me it might be possible to DIY this effect on the cheap using 80-grit glass bead sandblasting media from Harbor Freight. So I bought 25 lbs and ran some tests. The short version? It works! But, as usual, not quite like I expected it to. Keep reading for all the gritty (ha) details, or just hang tight and wait for the full tutorial, coming soon!

The title image shows my twenty-three test samples against a blank white projected screen. The unlabeled white image, as well as red, green, and blue screens, are available in the gallery at the bottom of this post.

1. Bare 3-ply cardboard. Same material used for middle board.
2. 1 coat white paint, unsanded.
3. 1 coat white paint, sanded.
4. 2 coats white paint, unsanded.
5. 2 coats white paint, sanded.
6. 1:15 beads:paint, unsanded.
7. 1:15 beads:paint, sanded.
8. 1:7 beads:paint, unsanded.
9. 1:7 beads:paint, sanded.
10. 1:3 beads:paint, unsanded.
11. 1:3 beads:paint, sanded.
12. 1:2 beads:paint, unsanded.
13. 1:2 beads:paint, sanded.
14. 1:1 beads:paint, unsanded.
15. 1:1 beads:paint, sanded.
16. Beads sprinkled over 2nd coat wet paint, excess blown off when paint dry.
17. Beads sprinkled over 2nd coat wet paint, excess blown and brushed off when paint dry.
18. 1:7 beads:glaze.
19. 1:5 beads:glaze.
20. 1:3 beads:glaze.
21. 1:2 beads:glaze.
22. 1:1 beads:glaze.
23. White melamine shelf section, sprayed with adhesive, sprinkled with beads, blown and brushed off when adhesive dry.

Bead/carrier mixtures were prepared (volumetrically) in disposable plastic cups and stirred for 1 minute each with a popsicle stick before application. Sanding was performed with a wooden block covered in 100 grit dry-use garnet abrasive paper. All carriers and bead/carrier mixtures were applied with 1″ disposable foam brushes. A fresh cup, brush, and stirrer was used for each mixture. Paint was “Kilz Casual Colors Ultra Bright White Flat,” clear glaze was “Valspar Signature Colors Clear Faux Protector Satin,” and spray adhesive was “3M Super77.”

My first concept, represented by the board to left, was to apply various mixtures of glass beads in common white interior latex paint, and then expose the embedded beads if necessary, by sanding. I prepared one too many cardboard blanks and, as an afterthought, decided I would see how well the process worked if I just sprinkled beads onto the wet paint instead of mixing them in beforehand. As a trained scientist, I should know better than to be surprised by the serendipitous results this method gave. As is evident, the bead/white paint mixtures show little if any increase in screen gain with increasing bead content, and little if any improvement over plain white paint, whether they are sanded or not.

However, the sprinkled-on beads of sample Q show a dramatic screen gain over all other samples. When the paint under the sprinkled-on beads was dry, the completely loose beads were easily removed by inversion of the surface, blowing, and light tapping. The beads that remained were not well fixed to the surface, but would not fall or blow off, either. Very light rubbing with the sanding block (or with a fingertip, as evident in sample P), was enough to remove these lightly-persistent beads and expose a thin layer of tightly-bound glass beads with the texture of sandpaper. This was the most effective surface I tested.

The middle board represents my attempt to achieve the effect of surface Q without the “sprinkling” contrivance. A clear liquid carrier was used this time. These samples R-V do show some noticeable screen gain over the opaque-carrier samples to left, but still do not really compare to sample Q. My tentative conclusion was that a thin “monolayer” of beads over a white surface is required for the high-gain effect, and sample W represents my attempt to test that hypothesis.

However, even though the spray adhesive is translucent and the underlying surface is bright white, the screen gain seen in sample W is still noticeably lacking compared to Q. My best hypothesis, at this point, is that a monolayer of glass beads each partially embedded in a white reflective medium is crucial to achieving the high-gain effect: Light enters each approximately-spherical bead from the viewing direction, and because the back of the bead is surrounded by a reflective white medium, bounces around and is reflected back out towards the viewer. In the absence of the reflective white medium surrounding the back half of each sphere, light from the viewing direction can exit the back of the bead and be trapped behind it.

Check out MAKE Volume 25:

MAKE Volume 25: Arduino Revolution
Give your gadgets a brain! Previously out of reach for the do-it-yourselfer, the tiny computers called microcontrollers are now so cheap and easy to use that anyone can make their stuff smart. With a microcontroller, your gadget can sense the environment, talk to the internet or other hardware, and make things happen in the real world by controlling motors, lights, or any electronic device.

» BUY or SUBSCRIBE

When I was a teenager, we had a distinctly impolite name for a pull tab that had been removed from the can with the rivet ring still intact, said name being based on a persistent urban legend about the alleged redemption value of these relatively rare tabs. I can assure you, dear readers, that legend has nothing to do with the reason I am familiar with this handy trick for removing pull tabs with the ring intact every time. Turns out, a tab with an intact rivet ring is quite useful for mounting to wooden frames as a picture hanger. And I, you know, have to hang up lots of pictures. Seriously.

More:

• Make: Projects — Light Switch Time Capsule
• Make: Projects — No-Holes Poster/Quilt Hanger
• Make: Projects — Install a Penny Countertop

Minnesota-based Make: Projects community member David Howard contributed a great how-to for making your own school mascot from scratch, complete with a cooling fan in the head piece to keep your furry mascot from overheating. Maybe your maker club or hackerspace needs a mascot too? Now you'll know how to make one. Thanks, David!

Minnesota-based Make: Projects community member David Howard contributed a great how-to for making your own school mascot from scratch, complete with a cooling fan in the head piece to keep your furry mascot from overheating. Maybe your maker club or hackerspace needs a mascot too? Now you'll know how to make one. Thanks, David!

My new Kinect is a very cool toy, but it was not lost on me, as I was plugging it in, that I'd given the Microsoft hive-mind a pretty sophisticated set of eyes and ears onto my living room. Sure, I suppose I could only plug it in when I'm using it, but I'm kind of a neat freak about my entertainment center wiring and I don't want to be digging the Xbox out every time I decide I want certain privacy. Some kind of lens-cap arrangement seemed the easiest solution, and making it out of the foam that the Kinect came packed in avoids the danger of picking some material that might scratch the device or otherwise be incompatible with it over the long term. Plus, it makes it easy for anyone who owns a Kinect (and still has the box) to go and do likewise, should they be so inclined.

More:

• Make: Projects — How to Run Mac OS on a PSP
• Make: Projects — How to Jailbreak an iPod touch or iPhone
• Make: Projects — iPalm Unlimited