66% or better

Built-in Coffee Table Lightbox

diydollarstorelightbox

[Flyingpuppy] sent us this tip about her cleverly-concealed pull-out lightbox drawer. Her resolution for the new year was to make more art, so she filled this coffee table with art supplies and decided she’d draw while relaxing in front of the television. She also wanted a lightbox nearby, which originally involved hacking the entire tabletop with some acrylic, but she eventually opted for a simpler build: and it’s portable, too! The drawer’s lights are battery-powered, so you can pull the entire thing out of the table and drag it onto your lap, if that makes drawing more comfortable.

[Flyingpuppy] sourced seven inexpensive LED units from her local dollar store, which she mounted to the back of the drawer with some screws. The rest of the drawer was lined with white foam board, the bottom section angled to bounce light up onto the acrylic drawing surface. Because she needs to open the case to manually flip on the lights, she secured the acrylic top magnetically, gluing a magnet to the underside of the foam board and affixing a small piece of steel to the acrylic. A simple tug on the steel bit frees the surface, providing access underneath. Stick around for a video below.

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axCut: An Open Source Laser Cutter

axCutopensourceLaserCutter

If you’ve always wanted a laser cutter and you have £1500 lying around (approx. $2500 as of today) — and you have access to a 3D printer — then you’ll want to take a look at [Damian's] open source laser cutter: axCut. The project has evolved over the last few months from some mockups in OpenSCAD to a working prototype.

You’ll want to dig through his blog posts as well as his YouTube channel for all the juicy details, but from what we can gather, [Damian] is on the home stretch. The current implementation includes a 40W CO2 laser with functioning laser control and an impressively quiet watercooling system. Although the build’s wiring remains a bit of a tangle, the prototype cuts (almost) as expected. His next hurdle is ironing out the air assist, which should prevent some fire hazard issues and keep the lens free of debris.

Check out a couple of videos after the break, and if you’re interested in getting into laser cutting but want to start smaller, have a look at the MicroSlice from a few months ago.

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Retro Modern Nixie Clock

timeface

[Reboots] is a humble hacker who enjoys nixie tubes. So when he saw an old General Electric battery charger for sale at a hamfest, he thought: “that case would make a nice clock…”

He was first exposed to nixie tube clocks a few years ago when his brother gave him a DIY nixie clock kit from [Peter Jensen's] website TubeClock.com – it was an easy build, and worked very well. It also introduced him to a unique driver for nixie tubes, an HV5622 high-voltage shift register made by Supertex inc. Compared to the traditional (and rare) 74141 nixie driver chips or discrete transistor drivers, the HV5622 is much smaller, requires less microcontroller I/O’s, and is not as picky when it comes to powering it.

The nixie tubes he chose for the project came from a lot sale on eBay, Russian surplus IN-12 tubes. He even managed to find an english datasheet for them!

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Making a Variable RF Signal Sampler

One of [Brian]‘s hobbies is Amateur Ham radio, in which it is usually required to check that the transmitted signals are within specifications. As it isn’t safe to connect the radio’s output directly to measuring equipment due to the high voltages involved, [Brian] made his own dedicated RF signal sampler. It works by using capacitive coupling between the signal you wish to sample and a high impedance output. The latter can then safely be connected to an oscilloscope or spectrum analyzer for monitoring.

In the picture you see above, the air gap between the core signal conductor and the output plays the role of a capacitor. By adjusting its length you can therefore vary the output signal’s voltage range. The sampler is built using a die-cast aluminium enclosure which is 52x38x27mm. As you may have guessed, due to the case geometry the output attenuation will depend on the signal’s frequency. [Brian] tested the unit using a 30MHz signal generator and printed this frequency attenuation graph while also varying the air gap.

Fail of the Week: Color Meter for Adjusting LEDs

fotw-color-meter

[John Peterson] answered our call to document your hacks by discussing what he learned while building this color meter. He conceived the project as a way to precisely match the color output of LEDs driven with a PWM signal. The thought was that it could sample an LED’s output, then use that data to calculate values necessary to match the color of other LEDs. This is a good idea when using LEDs of different types, but even diodes from the same production line can show variations in color output.

Of course this project wouldn’t be featured as a Fail of the Week if it worked as he had expected. It turns out the sensor that he used, an Avago ADJD-S371-QR999 on a SparkFun breakout board, takes very quick color readings. This is great for solid objects, but not great for a light source being switched on and off like the PWM LEDs.

We like it that [John] posted a list of lesson learned on the project. The real fail is in trying to use this particular sensor, but we figure there must be some way to get meaningful data through sampling. Check out the page for the retired sensor which also includes a link to the datasheet. Can you think of a firmware hack which would allow this hardware to sample so that the PWM value could be extrapolated through averaging or other calculations? Let us know in the comments.


2013-09-05-Hackaday-Fail-tips-tileFail of the Week is a Hackaday column which runs every Wednesday. Help keep the fun rolling by writing about your past failures and sending us a link to the story – or sending in links to fail write ups you find in your Internet travels.

Build a Cheap Airplane ADS-B Radio Receiving Tracking Station

airplane tracking with ADS-B radio receiving

Do you have commercial or general aviation flying over your home or near your home? Would you like to know more about these airplanes: identity, heading, speed, altitude and maybe GPS data along with even more information? Well then [Rich Osgood] has just the project for you and it’s not that expensive to set up. [Rick] demonstrates using a cheap USB dongle European TV tuner style SDR (software defined radio) tuner that you can get for under $30 to listen in on the Automatic Dependent Surveillance-Broadcast (ADS-B) 1090 MHz mode “S” or 978 MHz mode “UAT” signals being regularly transmitted from these aircraft.

He steps us through configuring the radio to use a better antenna for improved reception then walks through detailed software installation and set up to control the radio receiver as well as pushing the final decoded data to mapping software. This looks like a fascinating and fun project if you live near commercial airways. You won’t need a license for this hack because you’re only listening and not transmitting, plus these are open channels which are legal to receive.

There are some frequencies you are not legally allowed to eavesdrop on—private communications for residential wireless telephones and cellular frequencies to name just a few (Code of Federal Regulations Title 47, Part 15.9). So remember you do have to be careful and stay within legal frequencies even if your equipment is not restricted from such reception. Also note that just because you have a legal right to intercept conversations or data on some frequencies it could be illegal to publicly share the intercepted content or any details on the reception or decoding (just saying for the record).

We wonder if [Rick] could partner with [G. Eric Rogers] to upgrade [Eric’s] motorized telescope airplane tracking system to extrapolate the radio telemeter data into vector data so his Arduino can track without relying on a video feed. That merger might just get them both on a short TSA list.

Join us after the break for some extra informational links and to watch the video on setup, installation and usage of this cheap airplane tracking rig.

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Cheap (Free?) Mirror Replacement for your CO2 Laser

hdd mirrors

You know what’s expensive? Those little tiny little mirrors used in laser cutters — and they don’t last forever either! What if we told you it’s possible to make your own for free, using a broken hard drive?

[Tim Wehr] read about using HDD platters as mirrors on BuildLog.net, and decided to try it out for himself to see how well they work. He quickly salvaged an old hard drive and removed the ever so shiny platters. Using a few pieces of wood he clamped the platter and then cut circles out of it using a metal hole saw — the edges are a bit rough, so we’d recommend you invest in a diamond hole saw if you’re planning on trying this.

Some denatured alcohol polishing later and a bit of filing on the edges, and he had a replacement mirror. He then performed two tests using both the original and the HDD mirror on his CO2 laser. Almost identical cutting power. In fact, [Tim] muses that the HDD mirror looks like it cut slightly better even! Not bad!

[Thanks Riva!]