Hackaday Video: Safe Area Operation for Components (and Helicopters)

We’re back and this time talking about Safe Operating Area also called Safe Area Operation (SAO) which is short for the combination of things that can conspire to ruin your design. We also talk about helicopters.

Why take all of this time to discuss SAO you might ask, and what is that business about helicopters? Depending on the design there may be quite a bit of tedious math involved and sometimes there is just no avoiding it. Alternatively if you can get a feel for when math is and is not critical (based on design choices), it should be easier to get your next project up and running while still obeying the rules of the road.

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Piezoelectric Crystal Speaker for Clock Radio Is Alarmingly Easy to Make

cockadoodledooLet’s face it: most of us have trouble getting out of bed. Many times it’s because the alarm isn’t loud enough to rouse us from our viking dreams. [RimstarOrg]‘s homeowner’s association won’t let him keep a rooster in the backyard, so he fashioned a piezoelectric crystal speaker to pump up the volume.

[RimstarOrg]‘s speaker uses a Rochelle salt crystal strapped to a bean can diaphragm. In his demonstration, he begins by connecting an old clock radio directly to the crystal. This isn’t very loud at all, so he adds a doorbell transformer in reverse. This is louder, but it still won’t get [RimstarOrg] out of bed.

Enter the microwave oven transformer. Now it’s sufficiently loud, though it’s no fire bell alarm. He also demonstrates the speaker using a piezo igniter from one of those long barbecue lighters and a crystal radio earpiece. As always, the video is after the jump. [RimstarOrg] has a lot of relevant linkage in the summary so you can learn how to grow your own Rochelle crystals.

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Radar Imaging in your Garage: Synthetic Aperture Radar


Learn why you were pulled over, quantify the stealthiness of your favorite model aircraft, or see what various household items look like at 10 GHz. In this post we will describe the basics of Synthetic Aperture Radar (SAR) imaging, beginning with a historical perspective, showing the state of the art, and describing what can be done in your garage laboratory. Lets image with microwaves!

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Easily Silkscreen All the Things

Silkscreening isn’t as hard as it might seem. For instance, it’s easier than block printing because you don’t have to reverse the image. [Jimmy DiResta] shows how easy it is to put a silkscreening setup together and print on wood, metal, and, of course, t-shirts.

Once you decide on a design, print it out on an acetate sheet which can be run through a regular household printer. You can buy ready-made meshed frames or even entire kits, but [Jimmy] shows you how to build a simple frame and staple screen mesh to it. After sealing up the edges, mix up some photo emulsion, cover the mesh, and let it dry in a dark room.

When it’s dry, place your acetate on the screen and expose the emulsion using whatever light is available. [Jimmy] built a milk crate tower up to his fluorescent work light and exposed it for about four minutes. Now you’re almost ready to make your mark. Peel off the acetate and remove excess emulsion with a squirt bottle and compressed air. Dry the whole thing with a hair dryer and you’re done. Load up a squeegee with silkscreen ink and draw it from top to bottom with nice, even pressure, and you’ve got yourself a silkscreened thing.

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Fetching Etchings for Stainless Steel

What do you do when you have a 10-gallon brew kettle (or any other stainless steel or aluminium thing) with no volume markings (or Hack a Day logos)? If you’re [Itsgus], you use science to etch some markings with a few household items and a 9V and you call it a day.

[Itsgus] used 1/4c vinegar and 1/4tsp of salt to form an electro-etchant and applied it with a Q-tip connected to the negative terminal of a 9V. He used tape to connect a wire between the positive terminal and the kettle. The vinegar dissolves the salt, creating negatively charged ions. Connected correctly to a 9V, the process removes metal where the current flows. If you were to connect it in reverse,  you would add a small amount of metal.

The process only takes a few seconds. When the etchant starts to sizzle and bubble, Bob’s your uncle. Even though the stainless steel’s natural coat re-oxidizes over the etches, you should probably wash that thing before you brew. If you prefer adding metal to removing it, try electroplating copper on the cheap.

Make a Plastic Bender using Stuff You Already Have


The team over at [2PrintBeta] found they needed some unique plastic profiles for their 3D printer the Printupy. Unable to find a supplier with what they needed, they decided to try building their own inexpensive bending station, using stuff they already had.

Not too concerned with the longevity of the system (or perhaps the flammability?) they’ve taken a wooden board and routed a straight groove through the center of it. Using a power supply and some Nichrome wire — it’s done.

They admit it’s really not the most durable and that it requires constant supervision in case of flames — but it cost next to nothing to make, and actually works quite well! What we like about the following video is they also show us the design process, the laser cutting, and bending to create the final product.

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Make Your Electronics Lab in a Box


Unless your lucky enough to have a big personal workshop where you can have dedicated stations for all kinds of different tools, you’re probably like most of us here at Hack a Day — lots of projects, but never enough space.

[McLovinGyver] lives in a small flat, and finds setup and cleanup time often take longer than the project itself — so he’s come up with this handy dandy Electronics-Lab-in-a-Box (trademark pending).

The guide is really more of a series of pictures of his process of building the portable lab, but he shows off some great ideas of things you might want to include in your own personal version of it. The first step is deciding what tools you need in the lab. In general, your power supply unit, soldering iron, hot air re-flow and fume exhaustion are going to dictate the general size and shape of your lab — from there, it’s just a matter of filling in the gaps with the rest of your small tools.

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