Imagination Not Necessary With This Helicarrier Bed

We think we have another dad-of-the-year award to give out. When [Andy’s] five-year-old son won a Raspberry Pi 2 and needed a new bed, they decided to build the ultimate bed. It’s loosely based on the Helicarrier from S.H.I.E.L.D. and it’s packed with so much tech, you barely need to imagine anything to have fun with it.

It looks pretty simple from the outside, until you realize that the detailed little hatch on the side is actually a keypad secure entry automatic sliding door. Controlled by the Raspberry Pi, recordings of [JARVIS’] voice speak to you as you enter the belly of the ship, er, bed.

imag1813Inside are glowing display cases featuring some of his son’s favorite Marvel superhero’s equipment — ready for use. But what’s really cool is the command console.

The terminal is expertly crafted to look like something out of the movies, and with the Raspberry Pi 2, his son can play with it and fight off the bad guys. There’s even a sentry turret with camera on the outside, controlled from inside the bed.

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Polyakov Direct Digital Synthesis Receiver

Direct conversion receivers are popular among ham radio operators and others who build radios. Suppose you want to listen to a signal at 7.1 MHz. With a direct conversion receiver, you’d tune a local oscillator to 7.1 MHz, and mix it with the incoming signal. The resulting sum and differences of the input frequencies will include the audio of an AM signal on the desired frequency.

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Act Now And Receive the Prong Saver For Only $0.00!

Well, actually, you can’t buy this. But for [TVmiller’s] latest project he decided to have some fun with the video — so he made an infomercial for it.

Called the Prong Saver, the device clips onto any appliance’s electrical cord to help prevent you from accidentally pulling too hard and bending the electrical prongs. It’s basically a cord-tension alarm. The question is — can you hear it over the vacuum cleaner?

And just because he could, it’s solar powered. Because why the heck not? He built it using scraps he found around the workshop. That included a solar powered LED key chain, a small piezo speaker, an eyebolt and a compression spring. Anyway, check out the commercial after the break. It had us in stitches.

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Your First GNU Radio Receiver with SDRPlay

Although GRC (the GNU Radio Companion) uses the word radio, it is really a graphical tool for building DSP applications. In the last post, I showed you how you could experiment with it just by using a sound card (or even less). However, who can resist the lure of building an actual radio by dragging blocks around on a computer screen?

For this post and the accompanying video, I used an SDRPlay. This little black box has an antenna jack on one end and a USB port on the other. You can ask it to give you data about a certain area of the RF spectrum and it will send complex (IQ) data out in a form that GRC (or other DSP tools) can process.

The SDRPlay is a great deal (about $150) but if you don’t want to invest in one there are other options. Some are about the same price (like the HackRF or AirSpy) and have different features. However, you can also use cheap TV dongles, with some limitations. The repurposed dongles are not as sensitive and won’t work at lower frequencies without some external help. On the other hand, they are dirt cheap, so you can overlook a few little wrinkles. You just can’t expect the performance you’ll get out of a more expensive SDR box. Some people add amplifiers and converters to overcome these problems, but at some point it would be more cost effective to just spring for a more expensive converter.

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Trivia Lock Box Spices up Wedding Reception

Any hardware hacker will tell you, a significant other who embraces your passion is a keeper. [Nathan] found a keeper in [Jessica] – they even worked together on a hardware hack for their own wedding. The couple wanted an interactive element for their guests. Disposable cameras are getting a bit hard to find these days, so the solution was a trivia powered lock box designed and built by [Nathan] himself. Guests arrived at their tables to find locked boxes and cards with trivia questions about the couple. Only by answering the questions correctly would they unlock the box to access the prizes inside.

Each box consists of a Really Bare Bones Board, which is essentially an ATmega328 breakout board. The user interface consists of five tactile switches and a 16×2 character based LCD. The box is a clear Vaultz pencil box (Yes, the same brand Ahmed used for his clock). The final element is of course the locking mechanism. One of [Nathan’s] friends noticed that the Vaultz box latch was riveted in, and was spring loaded. It only took a bit of work to flip the latch from the outside to the inside. Cheap 9g micro servos from the far east pull the latch open with a string. The only thing we haven’t figured out is how [Nathan] closed the latches while they were inside the box. Obviously some black magic was involved! [Jessica] decorated the box with circuit traces created on her vinyl cutter.

On the eve of the big day, [Nathan] realized that his tactile switches were… not really switching. The superglue he had used to mount them had seeped into the switch body, freezing it solid. Nathan saved the project with a herculean effort of soldering 5 switches on each of 12 boxes the night before his own wedding.

What was in the box? Alka-Seltzer tablets. When added to vases filled with oil and water, the fizzy tablets turned the vases into mini lava lamps. The boxes also contained coins which were redeemable for Hawaiian Leis.

Click past the break to see the boxes in action on [Nathan] and [Jessica’s] big day and if you’re looking to build a fleet of hardware for your own wedding, take a look at the centerpieces [Bill Porter] created a couple of years ago.

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Radio Receiver or Art? Why not Both?

We’ve heard it said before that you should build things twice. Once to learn how to build it and the second time to build it right. [AA7EE] must agree. He was happy with his homebrew regenerative receiver that he called Sproutie. But he also wanted to build one more and use what he learned to make an even better receiver. The Sproutie Mark II was born.

This isn’t some rip off of an old P-Box kit either. [AA7EE] used a four-device RF stage with FET isolation back to the antenna and a regulated power supply. Plug in coils allow reception on multiple bands ranging from about 3 to 13 MHz. There’s an audio stage with multiple selectable audio filters, and–the best part–a National HRO tuning dial that is a work of art all by itself.

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Design Diary: Varactor-Tuned Regen Receiver

[QRP Gaijin] likes to build regenerative receivers. If you’ve ever built a serious one, you know there are (at least) two problems: One is you need a variable capacitor (hard to find these days). The other annoyance is that if you cover a wide frequency range, you probably need more than one coil.

[QRP Gaijin’s] latest radio design doesn’t have either of these problems. He uses a coil with a single pole double throw switch to bandswitch a single coil. There is no traditional main tuning capacitor. Instead a 1SV149 varactor provides the radio’s main tuning capacity (the diode tunes between 35 to 500 pF).

The post provides a nice design and a neat looking build in a Tupperware container (well… the outside is neat, at least; the inside is… best left inside the Tupperware). Better still, [QRP Gaijin’s] post details how he got to the final design, starting with the idea, and detailing the original design and the changes he made along the way. He also used data from an earlier build to limit how much the regeneration control has to be changed over wide frequencies and details how that changed the design. The prototype actually lacks the planned bandswitch, but will cover 3 to 30 MHz with the right coil.

There are certainly simpler regenerative receivers out there. However, the sophistication of this design along with the details of the designer’s thought processes makes this an interesting intermediate weekend project.

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