A VNA On A 200 Euro Budget

August 13, 2016 by Jenny List 24 Comments

If you were to ask someone who works with RF a lot and isn’t lucky enough to do it for a commercial entity with deep pockets what their test instrument of desire would be, the chances are their response would mention a vector network analyser. A VNA is an instrument that measures the S-parameters of an RF circuit, that rather useful set of things to know whose maths in those lectures as an electronic engineering student are something of a painful memory for some of us.

The reason your RF engineer respondent won’t have a VNA on their bench already will be fairly straightforward. VNAs are eye-wateringly expensive. Second-hand ones are in the multi-thousands, new ones can require the keys to Fort Knox. All this is no obstacle to [Henrik Forstén] though, he’s built himself a 30MHz to 6 GHz VNA on the cheap, with the astoundingly low budget of 200 Euros.

On paper, the operation of a VNA is surprisingly simple. RF at a known power level is passed through the device under test into a load, and the forward and reverse RF is sampled on both its input and output with a set of directional couplers. Each of the four couplers feeds what amounts to an SDR, and the resulting samples are processed by a computer. His write-up contains a full run-down of each section of the circuit, and is an interesting primer on the operation of a VNA,

[Henrik] admits that his VNA isn’t as accurate an instrument as its commercial cousins, but for his tiny budget the quality of his work is evident in that it is a functional VNA. He could have a batch of these assembled and he’d find a willing queue of buyers even after taking into account the work he’s put in with his pricing.

[Henrik]’s work has appeared on these pages several times before, and every time he has delivered something special. We’ve seen his radar systems, home-made horn antennas, and a very well-executed ARM single board computer. This guy is one to watch.

Thanks [theEngineer] for the tip.

Hackaday Prize Entry: A Good Electronics Learning Toolkit

August 12, 2016 by Brian Benchoff 60 Comments

The Maker movement is a wildly popular thing, even if we can’t define what it is. The push towards STEM education is absolutely, without a doubt, completely unlike a generation of brogrammers getting a CS degree because of the money. This means there’s a market for kits to get kids interested in electronics, and there are certainly a lot of options. Most of these ‘electronic learning platforms’ don’t actually look that good, and the pedagogical usefulness is very questionable. Evive is not one of these toolkits. It looks good, and might be actually useful.

The heart of the Evive is basically an Arduino Mega, with the handy dandy Arduino shield compatibility that comes with that. Not all of the Mega pins are available for plugging in Dupont cables, though – a lot of the logic is taken up by breakouts, displays, buttons, and analog inputs. There’s a 1.8″ TFT display in the Evive, an SD card socket, connectors for an XBee, Bluetooth, or WiFi module, motor drivers, a fast DAC, analog inputs, and a plethora of buttons, knobs, and switches. All of this is packed into a compact and seemingly sturdy plastic case, making the Evive a little more durable than a breadboard and pile of jumper wires.

You can check out a remarkably well produced video for the Evive below.

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Almost Fail Of The Week: Doing Surface Mount Reflow Wrong In Every Possible Way And Still Succeeding

August 12, 2016 by Gerrit Coetzee 34 Comments

Sometimes the best way to learn is from the success of others. Sometimes failure is the best teacher. In this case we are learning from [Tim Trzepacz]’s successive failures in his attempt to solder one board to another using a reflow oven. They somehow cancelled each other out, and he ended up with a working board. For those of you who have used a reflow oven, there will be eye rolling.

[Tim]’s first mistake was to use regular solder instead of paste. We can see how he got there logically; if you hand solder an SMD you melt solder onto the pads first to make it easier. However, the result was that he had two boards that wouldn’t sit flat on each other thanks to the globs of solder on the pads.

Not to be deterred, he laid the boards on top of each other and warmed up the oven to a toasty 650 degrees. Well, not quite. The dang oven didn’t turn to eleven, so he figured 500 would probably work too. Missing the hint entirely, he let his board bake in a nearly 1000F oven until he noticed some smoke which, he intuitively knew, definitely shouldn’t be happening.

The board was blackening, the solder mask was literally bubbling off the substrate, people were coming over to see the show, and he decided success was still possible. He clamped the heated boards together with a binder clip until they cooled. Someone gave him a lesson on reflow, presumably listened to through reddening ears.

Ashamed and defeated, he went home. However, there was a question in his mind. Sure it looks bad, but is it possible that the board actually works? After a quick test, the answer was yes. It loaded some code and an time later he was happily hacking away. Go figure.

DIY Smartwatch Based On ESP8266 Needs Classification

August 12, 2016 by Moritz Walter 20 Comments

Building your own smartwatch is a fun challenge for the DIY hobbyist. You need to downsize your electronics, work with SMD components, etch your own PCBs and eventually squeeze it all into a cool enclosure. [Igor] has built his own ESP8266-based smartwatch, and even though he calls it a wrist display – we think the result totally sells as a smartwatch.

His design is based on a PCB for a wireless display notifier he designed earlier this year. The design uses the ESP-12E module and features an OLED display, LEDs, tactile switches and an FT232R USB/UART interface. Our beloved TP4056 charging regulator takes care of the Lithium-ion cell and a voltage divider lets the ESP8266’s ADC read back the battery voltage. [Igor] makes his own PCBs using the toner transfer method, and he’s getting impressive results from his hacked laminator.

Together with a hand-made plastic front, everything fits perfectly into the rubber enclosure from a Jelly Watch. A few bits of Lua later, the watch happily connects to a WiFi network and displays its IP configuration. Why wouldn’t this be a watch? Well, it lacks the mandatory RTC, although that’s easy to make up for by polling an NTP time server once in a while. How would our readers classify this well-done DIY build? Let us know in the comments!

Wiggling Pokéball Detects Rare Pokémon

August 12, 2016 by Moritz Walter 3 Comments

[TJ Hunter] wanted to find some of the rarer Pokémon without draining his smartphone battery while staring on a screen. The handy ø 25 cm Pokéball he built to make the endless marches more tolerable detects nearby Pokémon and wiggles to alert its owner if there’s a rare catch in sight.

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Hacking When It Counts: Spy Radios

August 12, 2016 by Dan Maloney 33 Comments

World War II can be thought of as the first electronic war. Radio technology was firmly established commercially by the late 1930s and poised to make huge contributions to the prosecution of the war on all sides. Radio was rapidly adopted into the battlefield, which led to advancements in miniaturization and ruggedization of previously bulky and fragile vacuum tube gear. Radios were soon being used for everything from coordinating battlefield units to detonating anti-aircraft artillery shells.

But it was not just the battlefields of WWII that benefitted from radio technology. From apartments in Berlin to farmhouses in France, covert agents toiled away over sophisticated transceivers, keying in coded messages and listening for instructions. Spy radios were key clandestine assets, both during the war and later during the Cold War. Continue reading “Hacking When It Counts: Spy Radios” →

Hedberg Is A Bionic Hand Made From A Single Keurig

August 12, 2016 by Cameron Coward 11 Comments

Developing into a modern hacker and tinkerer requires a lot of things: electronics study, programming knowledge, and patience (among many other things). But, the most important quality a hacker can have is curiosity. The desire to see how things work is what drives most budding hackers towards the dismantling of family appliances and electronic gadgets.

Many end up scavenging parts from the things around the house for their first projects. But, with money and more ambitious builds comes the need to purchase parts off the shelf. There is, however, something to be said for the ingenuity that comes with building something solely with scavenged parts, and that’s what [Evan Booth] decided to do, in a spectacular fashion.

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