Function Generator Gets DIY Frequency Standard

April 8, 2018 by Tom Nardi 5 Comments

For those of us who like to wrangle electrons from time to time, there are some exceptional deals out there for low (or at least lower) cost imported test equipment. If you’re willing to part with a few hundred dollars US, you can get some serious hardware that a decade ago would have been effectively outside the reach of the hobbyist. Right now you can order a four channel oscilloscope for less than what a new Xbox costs; but which one you’ll rack up more hours staring at slack-jawed is up to you.

10 MHz output from DIY frequency standard

Of course, these “cheap” pieces of equipment aren’t always perfect. [Paul Lutus] was pretty happy with his relatively affordable Siglent SDG 1025 Arbitrary Function Generator, but found its accuracy to be a bit lacking. Fortunately, the function generator accepts an external clock which can be used to increase its accuracy, so he decided to build one.

[Paul] starts off by going over the different options he considered for this project, essentially boiling down to whether or not he wanted to jump through the extra hoops required for an oven-controlled crystal oscillator (OCXO). But the decision was effectively made for him when his first attempt at using a more simplistic temperature controlled oscillator failed due to an unfortunate misjudgment in terms of package size.

In the end, he decided to spring for the OCXO, and was able to use the USB port on the front panel of the SDG 1025 to provide the power necessary for the crystal to warm up and remain at operating temperature. After he got the oscillator powered, he just needed to put it in a suitable metal enclosure (to cut down external interference) and calibrate it. [Paul] cleverly used the NIST WWV broadcast and his ears to find when his frequency standard overlapped that of the source, therefore verifying it was at 10 MHz.

Hackers love accuracy, and accordingly, we’ve seen a number of frequency standard builds ranging from extremely cheap to luxuriously overkill.

Filter Your Pi And Be A Responsible Pirate

April 3, 2018 by Tom Nardi 20 Comments

At this point it’s pretty well-known that you can tack a long wire to the Raspberry Pi’s GPIO, install some software, and you’ve got yourself the worlds easiest pirate FM radio station. We say that it’s a “pirate” station because, despite being ridiculously easy to do, broadcasting on these frequencies without a license is illegal. Even if you had a license, the Raspberry Pi with a dangling bit of wire will be spewing out all kinds of unintentional noise, making it a no-go for any legitimate purposes.

Unfiltered output of Pi broadcasting on 107.3 MHz

In an effort to address that issue, [Naich] has written up a couple posts on his blog which not only discuss why the Pi is such a poor transmitter, but shows how you can build a filter to help improve the situation. You’ll still be a lawless pirate if you’re transmitting on FM stations with your Pi, but you won’t be a filthy lawless pirate.

In the first post, [Naich] shows us exactly what’s coming out of the wire antenna when the Pi is broadcasting some tunes on the default 107.3 MHz, and it ain’t pretty. The Pi is blasting out signals up and down the spectrum from 50 MHz to 800 MHz, and incredibly, these harmonics are in some cases stronger than the intentional broadcast. Definitely not an ideal transmitter.

[Naich] then goes on to show how you can build a DIY filter “hat” for the Pi that not only cuts down a lot of the undesirable chatter, but even boosts the intended signal a bit. The design is surprisingly simple, only costs a few bucks in components, and conveniently is powered directly from the Pi’s GPIO. It even gives you a proper antenna jack instead of a bare wire wound around a header pin.

We’ve seen plenty of projects utilizing the Raspberry Pi FM transmission hack, and while this mod still doesn’t make it perfect, it’s always nice to see an awesome hack made even better.

Learn What Did And Didn’t Work In This Prototyping Post-Mortem

March 30, 2018 by Donald Papp 16 Comments

[Tommy] is a one-man-shop making electronic musical things, but that’s not what this post is about. This post is about the outstanding prototyping post-mortem he wrote up about his attempt to turn his Four-Step Octaved Sequencer into a viable product. [Tommy] had originally made a hand-soldered one-off whose performance belied its simple innards, and decided to try to turn it into a product. Short version: he says that someday there will be some kind of sequencer product like it available from him, “[B]ut it won’t be this one. This one will go on my shelf as a reminder of how far I’ve come.”

The unit works, looks great, has a simple parts list, and the bill of materials is low in cost. So what’s the problem? What happened is that through prototyping, [Tommy] learned that his design will need many changes before it can be used to create a product, and he wrote up everything he learned during the process. Embedded below is a demo of the prototype that shows off how it works and what it can do, and it helps give context to the lessons [Tommy] shares.

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Storm Detector Modules: Dancing In The Rain

March 28, 2018 by Sean Boyce 18 Comments

Earlier, we had covered setting up an AS3935 lightning detector module. This detector picks up radio emissions, then analyzes them to determine if they are a lightning strike or some other radio source. After collecting some data, it outputs the estimated distance to the incoming storm front.

But that only gets you halfway there. The device detects many non-lightning events, and the bare circuit board is lacking in pizzazz. Today I fix that by digging into the detector’s datasheet, and taking a quick trip to the dollar store buy a suitable housing. The result? A plastic plant that dances when it’s going to rain!
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Scotty Allen Visits Strange Parts, Builds An IPhone

March 27, 2018 by Elliot Williams 19 Comments

Scotty Allen has a YouTube blog called Strange Parts; maybe you’ve seen his super-popular video about building his own iPhone “from scratch”. It’s a great story, and it’s also a pretext for a slightly deeper dive into the electronics hardware manufacturing, assembly, and repair capital of the world: Shenzhen, China. After his talk at the 2017 Superconference, we got a chance to sit down with Scotty and ask about cellphones and his other travels. Check it out:

The Story of the Phone

Scotty was sitting around with friends, drinking in one of Shenzhen’s night markets, and talking about how bizarre some things seem to outsiders. There are people sitting on street corners, shucking cellphones like you’d shuck oysters, and harvesting the good parts inside. Electronics parts, new and used, don’t come from somewhere far away and there’s no mail-ordering. A ten-minute walk over to the markets will get you everything you need. The desire to explain some small part of this alternate reality to outsiders was what drove Scotty to dig into China’s cellphone ecosystem.

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Everything You Wanted To Know About Transformers (But Were Afraid To Ask)

March 27, 2018 by Al Williams 18 Comments

[Jim Pytel] has a lot of very good instructional videos on his channel, and he recently added one you’ll enjoy on transformers. You probably know that transformers convert one AC voltage into another AC voltage. Some step up voltage, some step down voltage, and others simply pass voltage through but isolate the input from the output.

The 40 minute video covers basics including how the transformer works, the meaning of the turns ratio, and how transformers reflect impedance. You probably should understand how to compute AC power, but if you need a refresher [Jim] has a video for that, too.

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Iron Man Mask With A HUD!

March 25, 2018 by James Hobson 12 Comments

At some point, a child will inevitably dream of being a superhero. Not all children get the chance to see that dream made manifest, but a few take that destiny into their own hands. Redditor [Lord_of_Bone] — seizing at that goal — has built himself an Iron Man mask with an integrated HUD!

Relying on a conceptually similar project he’d previously built, much of the code was rehashed for this ‘Mark II’ version. Pieces of a smartphone holo pyramid act as projection surfaces — using a lens to focus the image to be viewed at such close distances — and a pair of OLED screens displaying the information. It’s a happy bonus that the lack of backlight results in only the text showing in the user’s field of view.

Instead of speaking with J.A.R.V.I.S., [Lord_of_Bone] is using a Raspberry Pi Zero W as the mask’s brain. Working past some I2C troubles between the OLED screens and an Enviro pHat required a whipped-up veroboard and a bit of hardware hacking. Cramming everything into the mask was no easy task — using Blutack and Sugru to bind them in the limited space — but the pHat had to be surface-mounted in the open anyways for atmospheric and light data.

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