hardware

1822 Articles

How’s The 60Hz Coming From Your Wall?

July 24, 2012 by 51 Comments

If you’ve ever wondered why NTSC video is 30 frames and 60 fields a second, it’s because the earliest televisions didn’t have fancy crystal oscillators. The refresh rate of these TVs was controlled by the frequency of the power coming out of the wall. This is the same reason the PAL video standard exists for countries with 50Hz mains power, and considering how inexpensive this method of controlling circuits was the trend continued and was used in clocks as late as the 1980s. [Ch00f] wondered how accurate this 60Hz AC was, so he designed a little test.

Earlier this summer, [Ch00f] bought a 194 discrete transistor clock kit and did an amazing job tearing apart the circuit figuring out how the clock keeps time. Needing a way to graph the frequency of his mains power, [Ch00f] took a small transformer and an LM311 comparator. to out put a 60Hz signal a microcontroller can read.

This circuit was attached to a breadboard containing two microcontrollers, one to keep time with a crystal oscillator, the other to send frequency data over a serial connection to a computer. After a day of collecting data, [Ch00f] had an awesome graph (seen above) documenting how fast or slow the mains frequency was over the course of 24 hours.

The results show the 60Hz coming out of your wall isn’t extremely accurate; if you’re using mains power to calibrate a clock it may lose or gain a few seconds every day. This has to do with the load the power companies see explaining why changes in frequency are much more rapid during the day when load is high.

In the end, all these changes in the frequency of your wall power cancel out. The power companies do the same thing [Ch00f] did and make sure mains power is 60Hz over the long-term, allowing mains-controlled clocks to keep accurate time.

Servos, Servos, And More Servos

July 21, 2012 by 22 Comments

For one reason or another, a lot of Hackaday readers are doing stuff with servos as of late. Here’s a few servo hacks that made their way into our tip line over the past day or so:

USB servo controller and a Stewart Platform

[Patricio] needed a way to control a bunch of servos for his thesis project. He came up with a USB servo controller (Spanish, here’s the translation) powered by a 40-pin PIC 18F microcontroller. The board connects to the USB port of a computer and supports up to 8 servos with 8 additional digital I/Os. Why all this horsepower? It’s for a Stewart Platform [Patricio] and his partner [Natalia] built.

Continuous rotation servos

Standard servos are usually limited to a rotation angle of somewhere between 140 and 160 degrees. Sometimes you need a continuous rotation servo, and those are a little more expensive. Every servo is a continuous rotation servo if you disable a the variable resistor as [Valentin] shows us. It’s a simple, if old, hack. It’s new to someone, though.

Eight servos on a Raspi

[Mikael] made a little board to attach to the GPIO header of his Raspberry Pi and control up to 8 servos. The board is running a serial interface with a small microcontroller on board. There’s nothing in the way of schematics or code, a testament for why you should always use a good email address when sending something into the HaD tip line. It seems [Mikael] is making a proper board, and we’ll more than happily give it a full post when it’s complete.

A Hardware Random Number Generator For Your FPGA

July 18, 2012 by 8 Comments

[Zach] sent in a project he’s been working on that brings hardware random number generators to common hardware you might have lying around. It’s called Whirlyfly and it turns an FPGA dev board into a hardware random number capable of outputting random bits over a USB connection at 3 Mbps.

Previously, the whirlygig ran on a custom CPLD that interfaced to a *nix box and provided high quality random numbers via /dev/hw_random. [Zach]’s efforts takes the core of the whirlygig and ports it to the very popular and inexpensive Papilio One FPGA dev board.

As for what [Zach] can do with his random number generator, it’s extremely easy to write a Monte Carlo experiment to approximate the value of π with a better accuracy than [Ptolemy] was able to muster 1900 years ago. There’s also the aspect of encryption, and – why you would do this we have no idea – making an uncompressable file is also possible.

Cracking Open An Ancient Avionics Gyroscope

July 16, 2012 by 26 Comments

This artificial horizon might as well have come from an alien ship. [Mike] somehow manages to get his hands on most interesting equipment, this time its a very old piece of avionics equipment. The mechanical gyroscope functioned as the artificial horizon, and he’s going to take us inside for a look. He doesn’t spend quite as much time on it as he did that thermal imaging camera, but this electro-mechanical odyssey is just as interesting.

To get the accuracy needed to help keep a plane in the air (well to keep the pilot well-informed anyway) the device needed to be very well manufactured. [Mike] comments several times along the way on how the different rotating parts are so well-balanced and machined that they seem nearly frictionless. It appears that a lot of the positional feedback depends on wirewound resistor rings which connect to a rotating piece via a series of very fine spring wires. As the parts rotate the resistance changes and that’s what gives the feedback. There are also mercury switches to help along the way.

He does his best to explain, but to us the inner workings are still a big mystery. See if you can get a clearer picture from the video after the break.

Continue reading “Cracking Open An Ancient Avionics Gyroscope” →

Rocket Telemetry From UAV Hardware

July 16, 2012 by 7 Comments

When we posted our call for rocketry hacks and builds, we expected to see a few altitude sensors and maybe a GPS module or two. Apparently, we forgot similar hardware is very popular in the remote-controlled aircraft world, and can be successfully added to a rocket as [Kevin] and his ArduPilot equipped J motor rocket showed us

The ArduPilot is a small Arduino comparable board designed for UAVs, quadcopters, and other whirligigs not powered by rocket motors. To get real-time telemetry from his rocket, [Kevin] attached a GPS receiver and an XBee transmitter. When launched on an H165 motor, [Kevin] was able to keep a radio lock on his rocket, allowing him to pull down data in real-time.

There are a few drawbacks to using the ArduPilot to collect flight data; the ArduPilot only reports ground speed, a somewhat useless feature if the vehicle is going straight up. Also, there is no way for [Kevin] to record data to an SD card; the ground team must be able to receive the XBee, lest bits of data go missing. For most rockets the radio issue shouldn’t be a problem. [Kevin] launched the same hardware on a J motor and was able to receive data from 3600 AGL.

Ouya, A $100 Game Console For Indie Developers

July 11, 2012 by 43 Comments

With the explosion of mobile gaming (due in no small part to the egg-bombing Angry Birds), the Ouya was bound to happen. It’s a $100 game console powered by Android that puts indie games right into your living room.

The specs for the Ouya means this cube of games isn’t a slouch: the console comes loaded with an NVIDIA Terga3 quad-core processor, 1 GB of RAM, 8 Gigs of flash storage, HDMI, WiFi, Bluetooth, and Android 4.0. A requirement for publishing games on the Ouya is making at least some of the game free to play, a la TF2 or LoL. In addition to being a video game console, Ouya will also pull down Twitch.TV streams allowing you to watch Starcraft championships and other e-sports on your big-screen TV.

Not only does the Ouya play games, its designers made the device easily hackable. There aren’t enough details to know exactly what this means, but we’re sure we’ll see a full-blown Linux distro running on the Ouya within a week of release.

As of this writing, the Ouya Kickstarter has already met their funding goal of $950,000 by taking in two million a freaking ton of money with 29 days left. This might become the most successful Kickstarter to date, and we can’t wait to see all the neat stuff and hacks for the Ouya in the near future.

Cheap As Chips Arduino Ethernet Shield

July 10, 2012 by 51 Comments

It’s no secret that Ethernet shields for the Arduino are a little expensive. With the official Ethernet shield selling for about $50 and other options not much cheaper, there’s a lot of room for improvement for Arduinofied Ethernet. [Boris] over at Open Electronics has a solution to this problem: his Ethercard powered by a $3 Ethernet controller.

The Ethercard uses the Microchip ENC28J60, a through-hole Ethernet controller. There isn’t much else on the board apart from an RJ45 jack, caps, resistors, and a cheap buffer chip. This board was designed to be easily produced, and we’re thinking it might be possible to etch this board at home.

There are a few drawbacks to this ENC28J60 Ethernet shield – the official Arduino Ethernet shield has a 10/100 Mbps connection where the Microchip-powered shield is limited to 10 Mbps. Given the reduced cost, ease of assembly, and the fact that it’s pretty hard to saturate a 100Mbps connection with an Arduino this flaw can be easily ignored.

Pretty neat, especially considering how much you can do with an Ethernet connection on your Arduino. Files and code available in the git.