PhD Crystal Radio Has Pizza Capacitor

May 26, 2016 by Al Williams 35 Comments

Crystal radios are old news, but great fun. What would happen if a PhD designed a crystal set? By PhD we mean Pizza Hut Deliveryperson and [John Greenlee] (who may not actually be a PhD of either kind; we don’t know) gives us a good idea with his crystal radio in a pizza box.

Pizza boxes aren’t the only food-related material in this radio. [John] makes a tuning capacitor out of cake rounds. Coincidentally, he decorates the tuning capacitor to look like a pizza.

The schematic itself is unremarkable–just a common crystal set. But the construction of the chassis and the capacitor make it an interesting project. If you know a young person that has any interest in radio, a crystal receiver is a rite of passage you shouldn’t deny them and this one is certainly a novelty. The picture of a pizza takes it even one step further than this YouTube build, which is nonetheless a good resource.

The instructions are well done, although some of the parts may be slightly hard to find. Germanium diodes and high-Z earphones are not as plentiful as they used to be, although you can still find them if you look.

This pizza box rig could be a gateway drug to more serious crystal radios. Or you could go smaller and try building one in a match box.

Hamvention: The Flea Market

May 26, 2016 by Brian Benchoff 26 Comments

Last weekend was Hamvention, the place you want to be on the third weekend in May. It is the world’s largest gathering of amateur radio enthusiasts, and an exceedingly large flea market containing all sorts of electronica.

The booths of Hamvention include a few notable Open Hardware folk, but for the most part, you’re looking a few big booths from Yaesu, an entire section dedicated to everything ARRL, and a few pop-ups from the usual suspects. Rigol was there, showing off their test equipment and selling the DS1052E oscilloscope for far more than it’s worth. The Rigol Zed is a much better buy, anyway.

As with any gathering of hams, antennas are everywhere. The largest by far was the tower at right. With a little more equipment, this antenna could do a moon bounce. It’s a shame the moon was full this weekend, and everyone went to bed early.

Giant antennas and an amateur radio trade show notwithstanding, the biggest draw is the flea market. You’re looking at about two football fields worth of parking spaces, filled with cars, tents, and collapsible tables and the strangest electronic devices you’ve ever seen. What was that like? Read on below.

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Hack Your Apartment: Keyless Entry With Little Effort

May 26, 2016 by Bob Baddeley 50 Comments

A typical buzzer for an apartment complex.

If you’ve been to an apartment complex with a locked front door, you’ve seen the buzzer systems. You press the corresponding button for the apartment you want and can talk to the resident. They can press a button to unlock the door briefly, and then you go up to their apartment and they don’t have to come down to let you in. But what if you’re the resident and you want to go for a run without your keys jingling in your pocket? What if you want to open it using just your smartphone?

I knew this was a silly problem, and everyone I told about it thought that for the amount of time and effort it might save, it was hardly worth it.

Challenge accepted.

How fast can I put this together using only parts I have around the apartment? Turns out about 2 hours.

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Fixing A Complicated Scrollwheel

May 26, 2016 by Elliot Williams 51 Comments

[Thomas] loves his Logitech MX Master mouse, which has a pretty elaborate scroll-wheel mechanism. Perhaps too elaborate; it broke on him after a week of use, just when he was getting used to the feature. So what did he do? Took it apart and fixed it, naturally. And as a bonus, we get a guided tour of the interesting mechanism. Check out his video below to watch it in action.

The weighted scroll wheel switches between two different modes, one with a detent like you’re probably used to, and one where the wheel is allowed to spin freely for long-distance travel. And to do this, it’s actually got a little motor inside that rotates a cam and throws a lever into the side of the scroll wheel for the detent mode, and pulls the lever out of the way for free spins. It must also have some logic inside that detects how quickly the scroller is spun because it re-engages as soon as the scroll wheel stops.

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This Is Your Epic Weekend To Hack Together Anything

May 26, 2016 by Mike Szczys 9 Comments

Wow how the time flies. It seems like only couple of weeks ago we were unveiling the film we shot at Salton Sea to launch this, our third global hacking initiative called The Hackaday Prize. What we want is to see you use those skills of yours to Build Something that Matters. Come up with a way to solve a technology problem and score yourself some sweet prizes. This weekend, anything goes.

The current challenge is called Anything Goes and the deadline to enter your project is Monday at 7am PDT. You need to show off a prototype of your idea, and have at least four (4) build logs about your work on your project page. Use the menu in the left sidebar of your project page to enter it in the Hackaday Prize (or in the Anything Goes round if you entered it during the first challenge).

Are you confused about what is happening here? Let’s hit the high points:

Every five weeks we start a new Challenge Round which is basically a whole new contest. You can enter now — it’s not too late. If you entered previously you may enter again.
From each challenge round we will select twenty projects to move on to the final round, and award them each $1,000 for their achievement.
When all five rounds are complete, those hundred final projects will be viewed by our expert judges who will pick five winners who get the big cash prizes: $150k, $25k, $10k, $10k, and $5k. The Grand Prize winner will also be offered a residency at the Supplyframe Design Lab in Pasadena, CA.
The moral of the story is: build something awesome because that’s what you do. But this weekend, make it something that helps people and you just might be one of the twenty moving on for a shot at a much larger purse.

It’s true, we have a lot of projects in the running for this year’s prize; right about 700 entries at the time of writing. But, like I said above, each Challenge is a new contest. We are just about to hit 300 entries for Anything Goes. Twenty will be finalists, which means your entry has about a 1 in 15 chance at this point. Make this weekend your personal hackathon — build it, document it, and don’t forget to submit it.

The HackadayPrize2016 is Sponsored by:

Arc from a flyback transformer power supply

A Cornucopia Of High Voltage Sources

May 26, 2016 by Steven Dufresne 39 Comments

Having hacked away with high voltage for many years I’ve ended up using a large number of very different high voltage sources. I say sources and not power supplies because I’ve even powered a corona motor by rubbing a PVC pipe with a cotton cloth, making use of the triboelectric effect. But while the voltage from that is high, the current is too low for producing the necessary ion wind to make a lifter fly up off a tabletop. For that I use a flyback transformer and Cockcroft-Walton voltage multiplier power supply that’s plugged into a wall socket.

So yes, I have an unorthodox skillset when it comes to sourcing high voltage. It’s time I sat down and listed most of the power sources I’ve used over the years, including a bit about how they work, what their output is like and what they can be used for, as well as some idea of cost or ease of making. The order is from least powerful to most powerful so keep reading for the ones that really bite.

Triboelectric Effect

You’ve no doubt encountered this effect. It’s how your body is charged when you rub your feet on carpet and then get a shock from touching a door knob. When you rub two specific materials together there’s a transfer of electrons from one to the other. Not just any two materials will work. To find out which materials are good to use, have a look at a triboelectric series table.

Materials that are on the positive end of the table will become positively charged when rubbed against materials on the negative end of the table. Those materials will become negatively charged. The further apart they are in the table, the stronger the charging.

Powering corona motor with triboelectricity

An example of where I’ve used this is to power the corona motor shown here. I vigorously rub a PVC pipe with a cotton cloth, and as the pipe emerges from the cloth, a sharp wire a few millimeters away takes the charge from the pipe. You can see this corona motor being powered by other power sources in the video here.

This would be considered an electrostatic power source because charge is accumulated on surfaces. Being insulating materials, that charge can’t move around.

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Raspberry Pi Cluster Build Shows How And What

May 26, 2016 by Richard Baguley 36 Comments

Raspberry Pi clusters are a dime a dozen these days. Well, maybe more like £250 for a five-Pi cluster. Anyway, this project is a bit different. It’s exquisitely documented.

[Nick Smith] built a 5-node Pi 3 cluster from scratch, laser-cutting his own acrylic case and tearing down a small network switch to include in the design. It is, he happily admits, a solution looking for a problem. [Smith] did an excellent job of documenting how he designed the case in CAD, prototyped it in wood, and how he put the final cluster together with eye-catching clear acrylic.

Of interest is that he even built his own clips to hold the sides of the case together and offers all of the files for anyone who wants to build their own. Head over to his page for the complete bill of materials (we didn’t know Pis were something you could order in 5-packs). And please, next time you work on a project follow [Nick’s] example of how to document it well, and how to show what did (and didn’t) work.

If 5 nodes just doesn’t do it for you, we suggest this 120-node screen-equipped monster, and another clear-acrylic masterpiece housing 40 Pis. This stuff really isn’t only for fun and games. Although it wasn’t Pi-based, here’s a talk at Hackaday Belgrade about an ARM-based SBC cluster built to crunch numbers for university researchers.