Monitoring Your Home Energy Use

July 18, 2012 by Mike Szczys 19 Comments

[Dave’s] been elbow-deep in mains voltage while building this home energy monitoring rig. He started with an approach that is different from most we’ve seen before. He wanted a system that could make a linear measurement to keep the accuracy as high as possible. His first thought was to use a opto-isolated linear amplifier to measure voltage, but ended up altering that plan since he’s looking for digital values when all is said and done.

He’s using an ADC on the mains side of the interface board, then sending the digital values to an Arduino with opto-isolators to keep the high voltage separate from the low. This does complicate things a little bit, as he has low voltage rails on either side; 0V and 5V to run the ADC on the mains side, and separate 0V and 5V to run the Arduino. To solve the problem of accurate current measurement over the full range a house uses he opted for a Programmable Gain Amplifier. It’s addressed via SPI and allows him to adjust resolution to facilitate accurate measurement of very small currents. We think anyone who has tried to measure small appliances (like an alarm clock) with a Kill-A-Watt and gets a zero reading will appreciate this.

The Arduino sends data via a serial connection, which [Dave] is currently graphing using his laptop. It would be nice to see a simple web-server using the Ethernet shield (or a different board like the RPi) so you could log in from the couch and see what’s been going on with your home grid.

Sensordrone Really Does Make Your Phone A Tricoder

July 18, 2012 by Mike Szczys 33 Comments

Sensordrone is a sensor-filled wireless dongle for use with a smart phone or other computer-like device. But perhaps this is better explained as the thing that makes your smart phone work exactly as the original Star Trek tricorders did. In one had you have the main unit that displays data, in the other you hold the sensor array which you can wave in front of things to take a reading.

This is really just a Bluetooth module, battery, a handful of sensors, and a breakout header all packaged in a nice case. But seeing it used in the video after the break does make us a little giddy. That breakout header gives you the option of connecting the Sensordrone to RS-232 or I2C devices. The first demonstration is a thermal printer being sent a print job from an Android phone. But the dongle isn’t just a pass-through. It comes with a range of sensors (those three windows in the case) for gas sensing, temperature, humidity, pressure, color sensing, and perhaps a few others.

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A Hardware Random Number Generator For Your FPGA

July 18, 2012 by Brian Benchoff 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.

Static Testing Hybrid Rockets For A Flight To Space

July 18, 2012 by Brian Benchoff 7 Comments

A team of rocketry enthusiasts at Boston University have been working on a small hybrid rocket motor that serves as a test bed for a larger, yet-to-be-designed power plant that will hopefully launch a rocket into space.

The static tests of the BURT Mk. II began last April with a series of tests using HTPB solid fuel and Nitrous Oxide as the oxidizer. The team had a series of failures – mostly due to the JB Weld seal on the igniter leads blowing out – but managed a 10 second burn on April 21st.

For later tests, a vector drive system built by a complimentary Boston University engineering group was used to control the direction of the thrust up to 12 degrees away from the axis of the engine. That’s an impressive bit of kit, especially considering the exhaust from the rocket reaches over 5000 degrees Fahrenheit.

Even though it’s summer now and the Boston University team is on a much deserved break, we can’t wait to see what the BURT team comes up with next year. Hopefully we’ll see a flight test that reaches the team’s goal of the Karman line.

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Sending A Raspberry Pi To 130,000 Feet

July 18, 2012 by Brian Benchoff 23 Comments

We knew this wouldn’t take long. [David] sent a high altitude balloon into the upper atmosphere last weekend using a Raspberry Pi as the brains of the payload.

[David]’s payload consisted of a Raspberry Pi, natch, with a Logitech webcam, GPS receiver, and six AA batteries wired into a LDO regulator with a monstrous heat sink to keep everything in the EPX foam enclosure relatively warm in the frigid rarefied air of near space.

A high altitude balloon isn’t much fun without some real-time data coming down from the upper atmosphere, so [David] used a Radiometrix NTX2 transmitter module (anyone know of an equivalent part for the USA?) that transmits a measly 10 milliwatts. Even though the transmitter has an ‘official’ range of 500 meters, [David] got word of image data being received in Northern Ireland, over 500 km away.

We’re pretty impressed with [David]’s flight – and the fact that his flight is now 12th place on the list of UK balloon altitude records – but now we’re wondering what could be done with another Raspi flight to near space. [David] had a lot of computing horsepower up there, enough to get images from a webcam and send them down to earth. Now we’re wondering what else could be done with a Raspberry Pi in space.

You can check out the GoPro video of the very fast decent after the break, or check out the received images on [David]’s Flickr.

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Hackaday Links July 18, 2012

July 18, 2012 by Jeremy Cook 13 Comments

Apollo 13 DJ controller Follow Up

[Adam] had a really impressive DJ controller build featured here recently. Many of you had more questions about the internals and such, so this post should clarify a few things. He’s still got a few more updates to make, but promises to reveal all if given enough time!

Noise Absorbing Headphones from Shooting Earmuffs

If the circuitry on your microphone-enabled shooting earmuffs has gone bad, the actual speakers may still be good. Why not convert them into some noise-blocking headphones? For that matter, if you’ve broken a pivot, there’s a simple solution for that too!

Help Choosing your CNC Router

If you’re in the market for a CNC router, but aren’t sure where to start, Ponoko has put together a handy pricing guide to several of the more popular DIY routers available.

DIY AC Unit

It’s very hot out, so what is one to do when your shop or garage is burning up? Why not build your own “AC unit?” Sure you have to supply your own ice, but at under $20 for this cooler-based unit, maybe it’s worth it. Here’s the Reddit thread explaining it as well as a picture of the finished product.

3D Topo Map on a CNC Router

Once you’ve purchased your CNC router using the above guide, why not make your own 3D top map? This tutorial features a map of Ross Island off of Antarctica. Why Ross Island? It was the first vector-format topo map found off of Wikimedia.

DMG Lib: Digital Mechanism And Gear Library

July 18, 2012 by Gerrit Coetzee 9 Comments

Reader, [klemens], suggested DMG Lib to us when we posted about a similar site. DMG-Lib is an amazing source of information. It’s primary downside is that a great portion of the text is in a language other than English, though in some ways this is a plus. Latin, Italian, German, and many other languages held the position of being the chief scientific language of the world long before English, and this repository holds entire books about mechanisms in those languages. Some of the books range all the way back to the 1500s. The mechanism animations are very good on this site and play smoothly. While it’s a little harder to search than KMODDL due to the language oddities, it’s still an extremely useful and interesting site to add to the hacker’s information toolbox.