3D Printing Custom LED Bar Graphs

[BikerGlen] wanted to spice up his zombie containment unit (see video below) so he designed and 3D printed some very cool looking bar graphs. Apparently, you can get curved bar graph LEDs, but only if you buy a fairly large quantity. Hand soldering discrete LEDs at the perfect angle would be frustrating, but with a 3D printed jig, it was a piece of cake.

The devices use a MAX6954 LED driver, so it needs very few parts and takes commands via SPI. The chips were not cheap, but the small size and high integration sold [Glen] on it.

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Sudo Google Assistant

A Raspberry Pi kicking around one’s workbench is a project waiting to happen — if they remain unused long enough to be considered a ‘spare.’ If you find you’ve been pining after an Alexa or your own personal J.A.R.V.I.S., [Novaspirit Tech] might be able to help you out — provided you have a USB mic and speaker handy — with an accessible tutorial for setting up Google Assistant on your Pi.

A quick run-through on enabling a fresh API client on Google’s cloud platform, [Novaspirit] jumps over to the Raspbian console to start updating Python and a few other dependencies. Note: this is being conducted in the latest version of Raspbian, so be sure to update before you get underway with all of your sudos.

Once [Novaspirit] gets that sorted, he sets up an environment to run Google Assistant on the Pi, authenticates the process, and gets it running after offering a couple troubleshooting tips. [Novaspirit] has plans to expand on this further in the near future with some home automation implementation, but this is a great jumping-off point if you’ve been looking for a way to break into some high-tech home deliciousness — or something more stripped-down — for yourself.  Check out the video version of the tutorial after the break if you like watching videos of guys typing away at the command line.

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A Very Large VU Meter Indeed

It used to be a must-have on any hi-fi, a pair of moving coil meters or LED bar graphs, the VU meter. Your 1980s boombox would have had them, for example. VU, for “Volume Units”, is a measure of audio level, and the fashion for its visual measure in consumer audio equipment seems now to have largely passed.

The LED bar graph VU meters were invariably driven by the LM3915, a chip that contains a resistor ladder and a stack of comparators which can drive LEDs directly. [Juvar] has taken an LM3915, and used it to drive a set of opto-isolated triacs which in turn drive a stack of appropriately coloured mains LED bulbs concealed within an Ikea Vidja lamp. The result is a huge and very bright VU meter that is as much a lighting effect as it is a measure of sound level.

He’s posted a video of the lights in action, and we’ve placed it below the break. There is a cameo appearance from his cat, and one can’t escape the feeling that it is wasted on a small room and would be at its best before a dance floor. Still, it’s a neat lighting effect and a new use for a classic integrated circuit.

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Reverse Engineering An Ultrasonic Car Parking Sensor

It has become a common sight, a must-have feature on modern cars, a row of ultrasonic sensors embedded in the rear bumper. They are part of a parking sensor, an aid to drivers for whom depth perception is something of a lottery.

[Haris Andrianakis] replaced the sensor system on hs car, and was intrigued enough by the one he removed to reverse engineer it and probe its workings. He found a surprisingly straightforward set of components, an Atmel processor with a selection of CMOS logic chips and an op-amp. The piezoelectric sensors double as both speaker and microphone, with a CMOS analogue switch alternating between passing a burst of ultrasound and then receiving a response. There is a watchdog circuit that is sent a tone by the processor, and triggers a reset in the event that the processor crashes and the tone stops. Unfortunately he doesn’t delve into the receiver front-end circuitry, but we can see from the pictures that it involves an LC filter with a set of variable inductors.

If you have ever been intrigued by these systems, this write-up makes for an interesting read. If you’d like more ultrasonic radar goodness, have a look at this sweeping display project, or this ultrasonic virtual touch screen.

Hackaday Prize Entry: Collaborative Water Purification

Look over any description of a water treatment plant, and you’ll find a description that includes the words, ‘coagulation tanks’. What are these treatment plants coagulating? You don’t want to know. How are they doing it? With chemicals and minerals. Obviously, there’s something else that can be done.

For their Hackaday Prize entry, [Ryan], [designbybeck], [Clint], [Wanda] and [Maker Mark] are investigating electrocoagulation. It’s an alternative to a frothy brew of chemicals that uses electricity to pull pollutants out of the water.

Right now, the tests are much smaller in scale than the tens of thousands of gallons you’d find at a water treatment plant. In fact, the test rig is only a 16-ounce mason jar. While this isn’t large enough to precipitate pollutants out of a household water supply, it is big enough for a proof of concept.

The team is using two electrodes for this build, one aluminum, and one iron. These electrodes are connected via alligator leads to the electronics board they’ve built. This electronics board is basically just an H-Bridge (used so they can reverse the polarity of the field emitter and prevent a buildup of gunk on the electrodes) and a few connectors to a power supply. The results are encouraging; they have a few time-lapse videos of a mason jar of dirty water clearing up with the power of electricity. It’s a great project with some great documentation. The team already has a bunch of updates on their project and instructions on how to replicate their hardware. You can check out those videos below.

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If The I And Q Of Software Defined Radio Are Your Nemesis, Read On

For those of us whose interests lie in radio, encountering our first software defined radio must have universally seemed like a miracle. Here is a surprisingly simple device, essentially a clever mixer and a set of analogue-to-digital or digital-to-analogue converters, that can import all the complex and tricky-to-set-up parts of a traditional radio to a computer, in which all signal procession can be done using software.

A quadrature mixer. Jugandi (Public domain).
A quadrature mixer. Jugandi (Public domain).

When your curiosity gets the better of you and you start to peer into the workings of a software defined radio though, you encounter something you won’t have seen before in a traditional radio. There are two mixers fed by a two local oscillators on the same frequency but with a 90 degree phase shift, and in a receiver the resulting mixer products are fed into two separate ADCs. You encounter the letters I and Q in relation to these two signal paths, and wonder what on earth all that means.

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Sip-and-Puff Touchscreens and Grilled Meat During World Create Day

In the last few weeks, we’ve been seeing a remarkable growth in the entries to The Hackaday Prize. This is due in no small part to World Create Day, a worldwide celebration of building stuff. It’s a worldwide buildathon with hackerspaces all around the globe. Now we’re getting a peek at the results of these gatherings, the videos are posted, and we’re simply gobsmacked by what was created during World Create Day.

Spinal Cord Hacks

The gang over at the Blusson Spinal Cord Center in Vancouver put together a two-day event for World Create Day. The goal of this event was to build a lipsync; a device that enables people with limited use of their hands to use touchscreen devices. It looks like a ray gun, but it’s actually a sip-and-puff device entered into last year’s Hackaday Prize.

Gardening in Cyprus

The Limassol Hackerspace in Cyprus had what is probably the best World Create Day out of all the hackerspaces who took part. Why? Grilled meat, of course.

Instead of trying to improve the entire world, the team at the Limassol hackerspace decided to think locally. Improving their own hackerspace with an automated irrigation system for their vegetable garden, planting vegetables, and building a barbecue took up most of the events of the day. One member even built a few serving platters out of sections of a eucalyptus trunk. These sections of tree cracked, but with the clever application of a CNC router, this hackerspace was able to inlay a few butterflies in the wood. It looks great, and even better with a pile of skewered, grilled meat.

The Osaka Makers’ Space

A few of the members at the Osaka Makers’ Space — like most of us — are interested in miniature robot battles. The first part of the event was, of course, spent tinkering with these tiny robots. A few members of the space made a breakout board for a BLE module, coding it so it could be voice-activated. No, that’s probably not the best way to control a battling robot, but you should do what you want, not what other people think is best.

Also during World Create Day, a few members of the space built three tiny chairs for children. The kids, unfortunately, were busy watching Sesame Street. But hey, at least the screw holes were doweled up. Also on the roster for Osaka’s World Create Day was fixing a broken MacBook Air. The fan quit, and the repair involved soldering wires from the fan to pads on the motherboard.

La Orotava

The folks at the Orotava Hackerspace put on a great event for World Create Day. Wait, where’s Orotava? It’s a town on the island of Tenerife, in the Canary islands. No, the birds are named after the islands, and the islands are named after the dogs.

While they didn’t have hordes of hackers come to a Hackaday meetup on an island in the middle of the Atlantic (St. Helena meetup, anyone?), the Orotava hackerspace did have a few people show up to discuss Hackaday Prize projects. The interesting projects generated from this discussion included an automatic farming robot, mobility problems for mental patients, and a low-cost bandsaw.