Precise Sundial Tells Time To The Minute

July 21, 2021 by Bryan Cockfield 16 Comments

We’re always a fan of an interesting or unique clock build around here, which often use intricate pieces of technology to keep time such as weights and gears, crystal oscillators, or even a global network of satellites in the case of GPS. While these are all interesting methods of timekeeping, the original method of tracking the sun is often forgotten. With this clock, the sun is the main method of keeping track of time, but unlike traditional sundials it has a number of advancements that let it keep surprisingly accurate time. (Google Translate from German)

While most sundials can only show hours, this one from [leon andré], a retired physicist, has a method for displaying minutes as well. It uses pinholes instead of shadows to keep track of the position of the sun, with the pinhole casting a bright spot of sunlight onto a diagram below. The diagram keeps track of the minutes, and consists of curved lines which help account for the sun’s changing path throughout a typical year. The dial keeps track of local solar time, as any sundial would, but by rotating it along its vertical axis it can be calibrated for the timezone that it’s in regardless of its position.

As far as clock builds go, one that is completely passive like this semi-digital sundial is fairly unique, especially for its accuracy. And, when set to local solar time, it will be the most reliable method of keeping time long-term than possibly any other clock we’ve seen before, as long as it’s not too cloudy outside. On the other hand, it is possible to augment a sundial with some modern technology as well.

Thanks to [Adrian] for the tip!

Analog Camera Goes Digital

July 15, 2021 by Bryan Cockfield 33 Comments

The digital camera revolution swept through the world in the early 2000s, and aside from some unique situations and a handful of artists still using film, almost everyone has switched over to digital since then. Unfortunately that means that there’s a lot of high quality film cameras in the world that are gathering dust, but with a few pieces of equipment it’s possible to convert them to digital and get some more use out of them.

[befinitiv]’s latest project handles this conversion by swapping in a Raspberry Pi Zero where the film cartridge would otherwise be inserted into the camera. The Pi is attached to a 3D-printed case which mimics the shape of the film, and also houses a Pi camera right in front of the location where the film would be exposed. By removing the Pi camera’s lens, this new setup is able to take advantage of the analog camera’s optics instead and is able to capture images of relatively decent quality.

There are some perks of using this setup as well, namely that video can be broadcast to this phone over a wireless connection to a computer via the Raspberry Pi. It’s a pretty interesting build with excellent results for a remarkably low price tag, and it would be pretty straightforward to interface the camera’s shutter and other control dials into the Raspberry Pi to further replicate the action of an old film camera. And, if you enjoy [befinitiv]’s projects of bringing old tech into the modern world, be sure to check out his 80s-era DOS laptop which is able to run a modern Linux installation.

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APRS Implemented At Low Cost And Small Size

June 15, 2021 by Bryan Cockfield 17 Comments

Before smartphones and Internet of Things devices were widely distributed, the Automatic Packet Reporting System (APRS) was the way to send digital information out wirelessly from remote locations. In use since the 80s, it now has an almost hipster “wireless data before it was cool” vibe, complete with plenty of people who use it because it’s interesting, and plenty of others who still need the unique functionality it offers even when compared to more modern wireless data transmission methods. One of those is [Tyler] who shows us how to build an APRS system for a minimum of cost and size.

[Tyler]’s build is called Arrow and operates on the popular 2 metre ham radio band. It’s a Terminal Node Controller (TNC), a sort of ham radio modem, built around an ESP32. The ESP32 handles both the signal processing for the data and also uses its Bluetooth capability to pair to an Android app called APRSDroid. The entire module is only slightly larger than the 18650 battery that powers it, and it can be paired with a computer to send and receive any digital data that you wish using this module as a plug-and-play transceiver.

While the build is still has a few limitations that [Tyler] notes, he hopes that the project will be a way to modernize the APRS protocol using methods for radio transmission that have been improved upon since APRS was first implemented. It should be able to interface easily into any existing ham radio setup, although even small balloon-lofted radio stations can make excellent use of APRS without any extra equipment. Don’t forget that you need a license to operate these in most places, though!

Coffee Stirrers Act As Lens For This Digital Straw Camera

May 6, 2021 by Dan Maloney 32 Comments

What happens when you mix over 23,000 coffee stirrers and a Raspberry Pi camera together? Probably nothing except for a mess, unless you very specifically pack the plastic straws and orient the camera just right. In that case, you get this very cool lenless digital straw camera that takes artfully ghostly images.

Image of Yoda photographed through many straws

Actually, lensless is a bit of a reach for [Adrian Hanft]’s creation. While the camera he’s using to grab the image has a lens, the objective, for lack of a better term, is just a tightly packed bundle of straws. We’ve seen this approach to photography before, but there the camera used film placed at the back of the straw bundles to capture the pixelated image.

Here, a ground glass screen stands in for the film; a long lightproof box behind that provide a place to mount a camera to capture the images. Cleverly, [Adrian] built the camera mount from Lego, allowing cameras and lenses to be quickly swapped out. A Nintendo gamepad controller talks to custom software running on a Raspberry Pi and allows the photographer to control exposure and scroll through pictures using a smartphone as a display. There’s a short build video below, for those who can’t get enough of straw-packing techniques.

As with the film version of this camera, we just love the look of the photographs that come from this — the texture of the straw honeycomb and the defocused subject make for a striking effect.

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The $50 Ham: A Simple WSPR Beacon

April 15, 2021 by Dan Maloney 27 Comments

I was having a chat recently with someone, and it surprised me that she had an amateur radio license. I suppose it shouldn’t have come as much of a surprise; after all, getting a ham radio license is a pretty common rite of passage in the life of a hardware hacker. I guess it surprised me because she’d never mentioned it in our past conversations, and as we talked about it, I learned why. “I got my license because I thought ham radio was about building radios, ” she said. “But it’s not.”

In a lot of ways, she is right about the state of ham radio. There was a time that building one’s own gear was as central to the hobby as getting on the air, and perhaps more so. Now, though, with radios as cheap as $30 and the whiz-bang gear that can make reaching out across the planet trivially easy, building your own radios has slipped down a few notches. But homebrewing is far from a dead art, and as we’ll see in this installment of “The $50 Ham”, a WSPR beacon for the HF bands is actually a fun and simple — and cheap — way for the homebrew-curious to get a taste of what it’s like to build your own transmitter.

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The $50 Ham: WSPR-ing Around The World

March 25, 2021 by Dan Maloney 18 Comments

Everybody has a bucket list, things to be accomplished before the day we eventually wake up on the wrong side of the grass. Many bucket-list items are far more aspirational than realistic; very few of us with “A trip to space” on our lists are going to live to see that fulfilled. And even the more realistic goals, like the trip to Antarctica that’s been on my list for ages, become less and less likely as your life circumstances change — my wife hates the cold.

Luckily, instead of going to Antarctica by myself — and really, what fun would that be? — I’ve recently been getting some of the satisfaction of world travel through amateur radio. The last installment of “The $50 Ham” highlighted weak-signal digital modes using WSJT-X; in that article, I mentioned a little about the Weak Signal Propagation Reporter, or WSPR. It’s that mode that let me test what’s possible with very low-power transmissions, and allowed me to virtually visit six continents including Antarctica and Sweden-by-way-of-Alaska.

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The $50 Ham: Digital Modes With WSJT-X

February 10, 2021 by Dan Maloney 33 Comments

As it is generally practiced, ham radio is a little like going to the grocery store and striking up a conversation with everyone you bump into as you ply the aisles. Except that the grocery store is the size of the planet, and everyone brings their own shopping cart, some of which are highly modified and really expensive. And pretty much every conversation is about said carts, or about the grocery store itself.

With that admittedly iffy analogy in mind, if you’re not the kind of person who would normally strike up a conversation with someone while shopping, you might think that you’d be a poor fit for amateur radio. But just because that’s the way that most people exercise their ham radio privileges doesn’t mean it’s the only way. Exploring a few of the more popular ways to leverage the high-frequency (HF) bands and see what can be done on a limited budget, in terms of both cost of equipment as well as the amount of power used, is the focus of this installment of The $50 Ham. Welcome to the world of microphone-optional ham radio: weak-signal digital modes.

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