Hackaday Links: Sunday, June 2nd, 2013


Who knew you could build your own digital computer out of paperclips? EMSL did a great feature on the guide which was published in 1968.

Trying to keep your Raspberry Pi from overheating? Make it log its core temperature on the web.

[Lennart] must be some kind of Eagle CAD guru. Check out these PCBs that incorporate his logo in a very artsy way.

No need for a tripod when you can just strap the video camera to your safety glasses for some POV project videos.

Turn your Pogoplug E-02 into a Shairport (Airplay clone) music hub. Just follow this guide which installs Arch Linux and all the supporting packages you need.

We don’t have the background to judge the quality of this build. But you have to admit it’s pretty neat to see a radio telescope built using a tin can and an umbrella.

Dead rodent email: get a notification every time your mouse trap springs.

Detecting galactic rotation with software defined radio


Last summer in the heyday of software defined radio via USB TV tuners we asked hackaday readers a question: Is anyone using everyone’s favorite method of SDR for radio astronomy? It took nearly a year, but finally there’s an awesome project to turn a USB TV tuner into a radio telescope. It’s from the fruitful mind of [Marcus Leech] (PDF warning), and is good enough to detect the rotation of the galaxy with a three-foot satellite dish.

News of [Marcus]‘ work comes to us from [Carl] over at RTL-SDR.com who has been keeping tabs on the advances of building a radio telescope in a backyard. He’s been collecting a lot of interesting tidbits including this gif showing an arm of the galaxy entering and leaving [Marcus]‘ telescope’s field of view over the course of a few hours.

Not only can [Marcus]‘ telescope record continium measurements – basically, a single-pixel camera sensitive to only one frequency – it can also produce spectral plots of the sky. Combine the ability to measure multiple frequencies at the same time with the Doppler effect, and [Marcus] can measure the rotation of the galaxy with a USB TV tuner. That’s just awesome in our humble opinion.

If you already have an RTL-SDR TV tuner and a largish satellite dish, [Marcus]‘ project should be fairly inexpensive to replicate; the feed assembly is made out of a coffee can, the amplifiers are repurposed satellite television equipment, and all the software – [Marcus]‘ own simple_ra tool for GNU Radio – is open source. Of course with a 3 foot diameter dish, it will be impossible to replicate the data from huge radio telescopes. Still, it’s an impressive piece of work that leaves us searching craigslist for an old C-band dish.

Hackaday Links: June 22, 2012

For when you want something huge machined

Turn your volume down for this video. It’s the HSM-Modal CNC mill carving a full-sized car out of styrofoam, applying clay to the foam core, and machining the clay at 50 meters per minute. Yes, we’ve seen this machine before, but never in action. It only took a little over 24 hours to make this full-size model car.

Microscope into a drill press

If you need to drill some PCBs, [wotboa] has a neat build for you. He built a micro drill press out of a microscope. It’s a damn good idea if you can find a quality microscope base; those things usually have exceptionally high precision. The ‘hack’ part is a $7 Harbor Freight rotary tool, some PVC pipe, and a PWM control for the motor – home-made, natch.

I’m telling you, they need to get [River] out of the library. Work on it [Moffat].

[Alan] made a TARDIS book case, and he decided to share the plans with us. Just the build to combat the severe lack of woodworking and Whovian stuff on Hackaday. Vashta Nerada hopefully not included.

Money can’t buy happiness, but you sure can sell it

[Greg] sent in some info on Disney’s ‘glow with the show’ hats they sell at the California Adventure park. For $25, you get a hat with RGB LEDs in the mouse ears that synchronize with the World of Color show every night. There’s a better description of the hats here, but we’re thinking these are very similar to the Coldplay Xylobands we saw at this year’s Grammys. Anyone want to tear some mouse ears apart?

An exceptionally low-tech radio telescope

[Impulse405] found a poor man’s radio telescope on Instructables and decided to share it with us. [Z0rb] found a 10-foot dish in the garbage and quickly absconded with this retro hardware. After adding a power supply and a meter-based total power receiver, [Z0rb] had a radio telescope that covered wavelengths from 850 to 2200 MHz.

Building a radio telescope for a school science project

The image above is a picture of  Hydrogen emissions from our galaxy. The cool thing about this picture is it wasn’t taken with millions of dollars worth of equipment; instead, only a few hundred dollars worth of ham radio gear was needed to get a picture of the Milky Way. [Shanni Prutchi], with the help of her dad [David] built this radio telescope in 5th grade, and even gave a presentation on this build at the National Radio Astronomy Observatory.

Instead of a gigantic satellite dish, [Shanni] used a loop yagi antenna to collect radio signals in the 1420 MHz band. These signals are amplified, filtered, and sent to an ICOM IC R-7000 receiver specially modified by [Shanni]‘s dad for radio astronomy.

After her telescope saw first light, [Shanni] and [David] decided to use their brand new toy to detect the passage of the sun. At around 10:00 am they pointed the telescope at where the sun would be at 1:30 pm. For the next few hours, the telescope gathered and integrated radio signals to make an awesome graph. Yep, [Shanni]‘s scope can detect radio waves coming directly from the sun.

Like a lot of us, [Shanni] was very much influenced by the movie Contact, something we brought up last week in a post on software-defined radio telescopes. This telescope was built in 2005, meaning [Shanni] couldn’t take advantage of any of the new advances in cheap software radios. We’re still waiting for someone to throw a Realtek SDR telescope together, so if you’ve got one send it in

Ask Hackaday: Has anyone built a radio telescope?

[Michael] sent in a question regarding the latest advances in software defined radios available for $20 on eBay:

I’ve been looking in to SDR lately, mainly for the possibility of using it for incredibly cheap radio astronomy. So far all I’ve found are whispers. I’m 18 and have very little experience, but I figured you might be able to help me find a little more info.

This really brings me back, [Michael]. I saw Contact in the theater (surprisingly, a rare case when the book and movie are equals), and in my childish exuberance went out and listened to lightning on Jupiter. The financial difficulties of expanding my setup meant the experiments stopped there, but at least I knew amateur radio telescopy was possible.

The latest and greatest advance in software defined radio – namely, a $20 TV tuner dongle – brings something new to the table. Instead of the thousands of dollars in gear that was required in 1997 when I last looked into this, it’s possible to set up a  passable radio telescope for under $100.

I’ll leave it to the Hackaday commentors to fill [Michael] in on the details, but here’s my suggestion:

Optimize your setup for 1420 MHz. There are three reasons for this: firstly, very few things in the universe absorb radio waves at a frequency of 1420MHz; there’s a reason it’s so often used in radio astronomy. Secondly, most government agencies around the world ban (or at least don’t look too kindly upon) transmitting on 1420 MHz. This frequency has been somewhat protected for use by astronomers. Thirdly, most of the Realtek TV tuner dongles have a frequency range of 64 – 1700 MHz, so it’s possible to receive 1420 MHz with this minimal setup.

As far as antennas go, your best bet is probably going to be one of those old C-band parabolic antennas from the 80s. That will make your telescope highly directional and give it a huge amount of gain. There is the problem of having a 20-foot-wide eyesore in your back yard, however. Alternatively, you could use a smaller DirecTV satellite dish, but I’m not making any promises with that. It’ll work, but it’s too small for an optimal setup.

I’ll concede the floor to anyone who has additional information. If you’ve built a radio telescope, send it in and I’ll put it up.