Circuit VR: Simple Buck Converters

July 6, 2018 by 19 Comments

The first thing I ever built without a kit was a 5 V regulated power supply using the old LM309K. That’s a classic linear regulator like a 7805. While they are simple, they waste a lot of energy as heat, especially if the input voltage goes higher. While there are still applications where linear regulators make sense, they are increasingly being replaced by switching power supplies that are much more efficient. How do switchers work? Well, you buy a switching power supply IC, add an inductor and you are done. Class dismissed. Oh wait… while that might be the best way to do it from a cost perspective, you don’t really learn a lot that way.

In this installment of Circuit VR, we’ll look at a simple buck converter — that is a switching regulator that takes a higher voltage and produces a lower voltage. The first one won’t actually regulate, mind you, but we’ll add that in a future installment. As usual for Circuit VR, we’ll be simulating the designs using LT Spice.

Interestingly, LT Spice is made to design power supplies so it has a lot of Linear Technology parts in its library just for that purpose. However, we aren’t going to use anything more sophisticated than an op amp. For the first pass, we won’t even be using those.

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An Optical Mouse Sensor For Robotic Vision

July 6, 2018 by 22 Comments

Readers with long memories will remember the days when mice and other similar pointing devices relied upon a hard rubber ball in contact with your desk or other surface, that transmitted any motion to a pair of toothed-wheel rotation sensors. Since the later half of the 1990s though, your rodent has been ever significantly more likely to rely upon an optical sensor taking the form of a small CCD camera connected to motion sensing electronics. These cameras are intriguing components with applications outside pointing devices, as is shown by [FoxIS] who has used one for robot vision.

The robot in question is a skid-steer 4-wheeled toy, to which he has added an ADNS3080 mouse sensor fitted with a lens, an H-bridge motor driver board, and a Wemos D1 Mini single board computer. The D1 serves a web page showing both the image from the ADNS3080 and an interface that allows the robot to be directed over a network connection. A pair of LiPo batteries complete the picture, with voltage monitoring via one of the Wemos analogue pins.

The ADNS3080 is an interesting component and we’d love see more of it. This laser distance sensor or perhaps this car movement tracker should give you some more info. We’ve heard rumors of them being useful for drones. Anyone?

Solar Pi Cluster Scours Internet For Nudes

July 6, 2018 by 50 Comments

There seems to be a universal truth on the Internet: if you open up a service to the world, eventually somebody will come in and try to mess it up. If you have a comment section, trolls will come in and fill it with pedantic complaints (so we’ve heard anyway, naturally we have no experience with such matters). If you have a service where people can upload files, then it’s a guarantee that something unsavory is eventually going to take up residence on your server.

Unfortunately, that’s exactly what [Christian Haschek] found while developing his open source image hosting platform, PictShare. He was alerted to some unsavory pictures on PictShare, and after he dealt with them he realized these could be the proverbial tip of the iceberg. But there were far too many pictures on the system to check manually. He decided to build a system that could search for NSFW images using a trained neural network.

The nude-sniffing cluster is made up of a trio of Raspberry Pi computers, each with its own Movidius neural compute stick to perform the heavy lifting. [Christian] explains how he installed the compute stick SDK and Yahoo’s open source learning module for identifying questionable images, the aptly named open_nsfw. The system can be scaled up by adding more Pis to the system, and since it’s all ARM processors and compute sticks, it’s energy efficient enough the whole system can run off a 10 watt solar panel.

After opening up the system with a public web interface where users can scan their own images, he offered his system’s services to a large image hosting provider to see what it would find. Shockingly, the system was able to find over 3,000 images that contained suspected child pornography. The appropriate authorities were notified, and [Christian] encourages anyone else looking to search their servers for this kind of content to drop him a line. Truly hacking for good.

This isn’t the first time we’ve seen Intel’s Movidius compute stick in the wild., and of course we’ve seen our fair share of Raspberry Pi clusters. From 750 node monsters down to builds which are far more show than go.

NanoPi Cluster Is Quiet, Cool And Has Blinky Lights

July 5, 2018 by 13 Comments

We’ve seen the supercomputer cluster work of [Nick Smith] from the UK before, but his latest build is quite lovely. This time around, he put together a 96-core supercomputer using the NanoPi Fire3, a Raspberry Pi alternative that has double the number of cores. His post takes you through how he built the supercomputer cluster, from designing the laser-cut acrylic case to routing the power cables.

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LEDs Make An “Analog” Wristwatch

July 5, 2018 by 6 Comments

If you just came down in the last shower, you’re probably used to living in a world where LEDs are cheap, awesome, and practically everywhere. Spare a thought for those of us who lived before the invention of high brightness LEDs – these things still amaze us! A great example of how far we’ve come is this “analog” watch build by [Kevin], featuring no less than 73 of the critters.

The microcontroller running the watch is an STM32, chosen for its easy programmability. It’s running the LEDs in an emulation of the dial of an analog clock, hence the high part count. Naturally, it’s no simple task to cram 73 LEDs and all the necessary connections into the confines of a watch-sized PCB. [Kevin] goes into great detail about the challenges involved, from routing the traces to a tricky power draw problem caused by some odd blue LEDs.

Watch builds are always fun, and they make great conversation pieces for when you want to amaze strangers with your tales of battles fought in the PCB design suite. Now check out this similar build with an entirely different style. 

 

Casting Tour-De-Force Results In Swashplate For Scale Helicopter

July 5, 2018 by 21 Comments

While quadcopters seem to attract all the attention of the moment, spare some love for the rotary-wing aircraft that started it all: the helicopter. Quads may abstract away most of the aerodynamic problems faced by other rotorcraft systems through using software, but the helicopter has to solve those problems mechanically. And they are non-trivial problems, since the pitch of the rotors blades has to be controlled while the whole rotor disk is tilted relative to its axis.

The device that makes this possible is the swashplate, and its engineering is not for the faint of heart. And yet [MonkeyMonkeey] chose not only to build a swashplate from scratch for a high school project, but since the parts were to be cast from aluminum, he had to teach himself the art of metal casting from the ground up. That includes building at least three separate furnaces, one of which was an electric arc furnace based on an arc welder with carbon fiber rods for electrodes (spoiler alert: bad choice). The learning curves were plentiful and steep, including getting the right sand mix for mold making and metallurgy by trial and error.

With some machining help from his school, [MonkeyMonkeey] finally came up with a good design, and we can’t wait to see what the rest of the ‘copter looks like. As he gets there, we’d say he might want to take a look at this series of videos explaining the physics of helicopter flight, but we suspect he’s well-informed on that topic already.

[via r/DIY]

Junk Bin Self Balancing Bot With ESP8266

July 5, 2018 by 10 Comments

As we all know, sometimes the projects we plan simply never materialize. You have an idea, maybe even buy some of the parts you need, and then…nothing. Maybe you changed your mind, or maybe the idea was never that good to begin with. In any event, time marches on, the parts pile up, and the ideas come and go. Such is the life of the hacker.

[Andrius Mikonis] writes in to tell us how his graveyard of abandoned projects ended up providing exactly what he needed to embark on a project he’s been fascinated with for years: the two-wheel self balancing robot. He started with a motor and wheel set that was originally intended to be part of a rover, added an accelerometer, and tied the whole thing together with an ESP-01 he had lying around. The final result certainly looks the part, and goes to show that projects don’t always need to be 1000 hour labors of love to accomplish their goals.

The construction of this little bot is simple in the extreme. A piece of plywood makes up the primary structure, with the wheels glued to the bottom and the electronics taking up residence in the top. It’s powered by two lithium battery cells that were salvaged out of an old laptop, with a DC-DC buck converter to provide a stable 3.3 VDC for the ESP-01 and MPU6050 accelerometer. To control the motors themselves, [Andrius] is using a cheap L293 controller that he found on eBay.

For interactive control, [Andrius] is making use of the ESP’s Wi-Fi to provide a web-based interface. This lets you control the bot from essentially any device that has a browser, rather than having to use a dedicated hardware transmitter.

Self-balancing robots of various levels of complexity are a relatively common project in the hacker world. There’s just something magical about the way they scoot around, seeming to defy gravity.