A Primer on Buck (and Boost) Converters

We all know that the reason the electrical system uses alternating current is because it’s easy to step the voltage up and down using a transformer, a feature which just isn’t possible with a DC system… or is it? Perhaps you’ve heard of mysterious DC-DC transformers before but never really wanted to look at the wizardry that makes them possible. Now, SparkFun Director of Engineering [Pete Dokter] has a tutorial which explains how these mysterious devices work.

Known as buck converters if they step the input voltage down and boost converters if they step the voltage up, [Pete] explains how these circuits exploit the properties of an inductor to resist changes in current flow. He goes into exquisite detail to explain how components like transistors or MOSFETs are used to switch the current flow to the inductor very rapidly, and just exactly what happens to the magnetic field which makes these devices possible.

The video gives a good amount of background knowledge if you’ve always wanted to understand these devices a little bit better. There are also a few projects floating around that exploit these devices, such as one that uses an AVR microcontroller to perform the switching for a small circuit, or another that uses the interesting properties of these circuits to follow the I-V curve of a solar panel to help charge a bank of batteries. The possibilities are endless!

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Drums Anywhere!

The students over at Cornell’s School of Electrical and Computer Engineering have been hard at it again with their senior projects. This time, it’s the very tiny and portable drumset dubbed Drums Anywhere by its creators [Shiva Rajagopal] and [Richard Quan]. Since there are other highly portable instruments like roll-up pianos, they suppose there should be a portable drum kit that actually sounds like drums, and this ECE duo have hit the metaphorical and physical drum on the head… except that this project doesn’t actually use physical drums to make sound.

The project consists of two 3D-printed box-like sensors with velcro straps that can be attached to any drumstick-shaped object that might be lying around. Inside the box is a flex sensor and a tiny microphone which report the “beats” to a microcontroller when they strike another object.

On the software side, there are two sampled sounds stored in the microcontroller but they plan to add more sounds in the future. The microcontroller outputs sound to a pair of speakers, and the sensors are sensitive to force, so the volume can range from almost inaudible all the way up to [John Bonham]-style booms. This could also be theoretically expanded to include more than two “beat boxes” for extra sounds, or be wireless. The options are virtually limitless, although the team notes that they are limited by the number of interrupts and ADC converters on their particular microcontroller, an ATmega1284.

This is another interesting take on a having drumset without the drums, and definitely expands the range of what a virtual drum set can do. It’s also great to see interesting projects coming from senior design classes! Be sure to check out the video after the break.

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Keystroke Sniffer Hides as a Wall Wart, is Scary

For those of us who worry about the security of our wireless devices, every now and then something comes along that scares even the already-paranoid. The latest is a device from [Samy] that is able to log the keystrokes from Microsoft keyboards by sniffing and decrypting the RF signals used in the keyboard’s wireless protocol. Oh, and the entire device is camouflaged as a USB wall wart-style power adapter.

The device is made possible by an Arduino or Teensy hooked up to an NRF24L01+ 2.4GHz RF chip that does the sniffing. Once the firmware for the Arduino is loaded, the two chips plus a USB charging circuit (for charging USB devices and maintaining the camouflage) are stuffed with a lithium battery into a plastic shell from a larger USB charger. The options for retrieving the sniffed data are either an SPI Serial Flash chip or a GSM module for sending the data automatically via SMS.

The scary thing here isn’t so much that this device exists, but that encryption for Microsoft keyboards was less than stellar and provides little more than a false sense of security. This also serves as a wake-up call that the things we don’t even give a passing glance at might be exactly where a less-honorable person might look to exploit whatever information they can get their hands on. Continue past the break for a video of this device in action, and be sure to check out the project in more detail, including source code and schematics, on [Samy]’s webpage.

Thanks to [Juddy] for the tip!

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Stereo Audio on a PIC32

The PIC microcontrollers are powerful little devices, and [Tahmid] is certainly pushing the envelope of what these integrated circuits can do. He has built (for educational purposes, he notes) an audio player based on a PIC32 and a microSD card. Oh, and this microcontroller-based audio player can play in stereo, too.

The core of the project is a PIC32MX250F128B microcontroller. 16-bit 44.1kHz WAV files are stored on the microSD card and playback is an impressive 12-bit stereo audio. It can also play back 8-bit files (with some difficulty). [Tahmid] programmed the interface to work through the serial port and it is very minimalistic, mostly because this was a project for him to explore audio on a microcontroller and wasn’t to build an actual stand-alone audio player that he would use from day to day.

Still, even though the project isn’t ready to replace your iPod, the core audio-processing parts are already done if you want to try to build on [Tahmid]’s extensive work. You could even build a standalone audio player like this but have it play high-quality 12-bit stereo audio!

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Everyone’s Favorite Energy Meter Hack, Now Wireless

[Kalle] is at it again with more hacks on electricity use meters. This time, the meter has been hacked to stream their data over the aether wirelessly. Now, data can be grabbed from multiple devices simultaneously, making the possibilities for home energy monitoring limitless

The first project [Kalle] did involved finding a meter from China with capabilities similar to (and cheaper than) the Kill-a-Watt meters. Unlike the Kill-a-Watt which spits out analog values, the Chinese meter sent digital information out on a ribbon cable with the bus lines labeled. Since the meter was so hackable, [Kalle] took it even further in this hack.

With those pesky wires out of the way, the device now uses an Arduino Pro Mini to sniff the energy meter’s data stream. Then it transmits the data wirelessly with a nRF34L01+ transceiver. As a perk, all of these chips fit inside the case of the energy meter, making this a very tidy hack indeed. The project code an incredible amount of detail is available on the project site, so be sure to check this one out for all of your energy monitoring needs!

Redundant Automated Water Filler For Your Coffee

We’ve always wondered why we have indoor plumbing if it isn’t hooked up to our coffee pots. We probably drink as much coffee as water anyway, so why not just hook up a water line to refill the pot? [Loose Cannon] aka [LC] has been working on just that problem, with a whole lot of extra features, creating a very robust automatically-filled, gravity-fed, vacuum-sealed water tank for whatever appliance you have that could use it, including your coffee pot.

[LC] tapped into the 1/4″ water line from the ice maker, which has the added bonus of being a common size for solenoid valves. He’s using an eTape sensor to measure the water level in the reservoir, but he ALSO is using a flow meter in the line itself to double-check that the reservoir won’t overflow. The flow meter allows a hard limit to be set for the maximum amount of water allowed into the tank. He’s used an Arduino Micro to tie the project together, which also handles a real-time clock so the tank can be filled on a schedule.

The tank that [LC] was trying to fill was vacuum-sealed as well, which made things a little trickier. Without a vacuum on the tank, the water would just run out of the overflow valve. This is an interesting project that goes way beyond the usual automatic water supplies for coffee pots we’ve seen before.

Automated Bed Warmer Control for Chilly Nights

For most of the Northern Hemisphere, winter is in full swing right now. That means long, chilly nights. We assume [LC] is in one of these climes because it seems like his bed warmer wasn’t doing quite a good enough job of getting his bed up to a reasonable temperature before he climbed in. To alleviate some of his discomfort, he hacked into the control unit and added some automation.

The original controller uses a mechanical potentiometer to set the heat level. [LC] added a digital potentiometer which he can switch to in order to allow the automation (using a real-time clock to handle scheduling) to take over control of the bed warmer. This also preserves the original functionality of the controller. There is also an Arduino involved which handles the override from mechanical to digital potentiometer when a capacitive touch sensor is activated. This means that when someone attempts to take manual control of the device, the Arduino can switch the override circuit off.

There is quite a bit of detail on the project site about this hack, including the source code for the controller. [LC] also mentions that this could be interfaced to the web to allow remote control of the bed warmer. This is a great hack, and also fits into the idea of heating the person, not the room.