Using multiwall carbon nanotubes, researchers at Georgia Institute of Technology have created what they say are the first optical rectennas–antennas with rectifiers that produce DC current. The work could lead to new technology for advanced photodetectors, new ways to convert waste heat to electricity and, possibly, more efficient ways to capture solar energy.
A paper in Nature Nanotechnology describes how light striking the nanotube antennas create a charge that moves through attached rectifiers. Challenges included making the antennas small enough for optical wavelengths, and creating diodes small enough and fast enough to work at the extremely short wavelengths. The rectifiers switch on and off at petahertz speeds (something the Institute says is a record). Continue reading “Optical Rectenna Converts Light to DC”
Cell phones have killed many industries. It is getting harder and harder to justify buying an ordinary watch, a calculator, or a day planner because your phone does all those things at least as well as the originals. Cell phones have cameras too, so the days of missing a shot because you don’t have a camera with you are over (although we always wonder where the flood of Bigfoot and UFO pictures are). However, you probably still have a dedicated camera tucked away somewhere because, let’s face it, most cell phone cameras are just not that good.
The Raspberry Pi camera is about on par with a cheap cell phone camera. [Martijn Braam] has a Nikon camera, and he noticed that he could get a Raspberry Pi camera with a C-mount for lenses. He picked up a C to F adapter and proceeded to experiment with Nikon DSLR lenses on the Raspberry Pi camera. (Update: We’ve changed the link to [Martijn’s] original blog post instead of a copy of it.)
Continue reading “Hacking a Pi Camera with a Nikon Lens”
After building devices that can read his home’s electricity usage, [Dave] set out to build something that could measure the other energy source to his house: his gas line. Rather than tapping into the line and measuring the gas directly, his (much safer) method was to simply monitor the gas meter itself.
The major hurdle that [Dave] had to jump was dealing with an ancient meter with absolutely no modern electronics like some other meters have that make this job a little easier. The meter has “1985” stamped on it which might be the manufacturing date, but for this meter even assuming that it’s that new might be too generous. In any event, the only option was to build something that could physically watch the spinning dial. To accomplish this, [Dave] used the sensor from an optical mouse.
The sensor is surrounded by LEDs which illuminate the dial. When the dial passes a certain point, the sensor alerts an Arduino that one revolution has occurred. Once the Arduino has this information, the rest is a piece of cake. [Dave] used KiCad to design the PCB and also had access to a laser cutter for the enclosure. It’s a great piece of modern technology that helps integrate old analog technology into the modern world. This wasn’t [Dave]’s first energy monitoring system either; be sure to check out his electricity meter that we featured a few years ago.
This rather bulky looking wall wart is actually a computer mouse. Sure, it may cause your hand to cramp horribly if used for any length of time. But some would say it’s worth that for the hipster value of the thing.
The rather odd shape is somewhat explained by the fact that this was sourced from Ikea. After gutting the transformer found inside the plastic case he had plenty of room to work with. He drilled a hole so that the sensor from a Logitech USB optical mouse can pick up the movement of the mouse. He also got pretty creative when it came to the buttons. The two prongs of the wall plug pivot horizontally to affect the momentary press switches inside.
After the break you can see a quick demo of the project. [Alec] doesn’t consider it to be complete. He wants to make a couple of improvements which include adding weight to make it feel more like the original wall wart, and finding a way to hide the hole he drilled for the sensor.
Continue reading “Wall wart computer mouse”
[Sebastian] wrote in to update us about the optical sensor project he started a couple of years ago. You’ll find his most recent update here, but there are four different post links after the break that document various parts of his progress.
You may not recall the original project, but he was looking to add resolution and sensitivity to the keystroke of an electric keyboard. With the sensors built, he started experimenting with using the force data to affect other parts of the sound. His post back in January shows this bending the pitch as the keys receive more force from the player.
In March he installed the sensor array in an old piano. The video he posted where he plays the piano, but we hear the sound generated from the sensor inputs. We’ve embedded it after the break.
Last week he published two posts. They cover a redesign of the sensor boards, and the panelization work he’s done to help bring down manufacturing costs. The base unit was redesigned to use an AT90USB microcontroller which consolidates the separate chips used in the previous version.
Continue reading “Update: many improvements to optical-sensor-based piano”
In an attempt to add technology to his brewing process [hpux735] build a sensor rig that monitors bubbles and pressure during fermentation. What does this have to do with brewing great beer? We’re not sure and neither is [hpux735], but he’s got some preliminary readings to spark your imagination.
The bubble sensor itself was inspired by a SparkFun Tutorial where fermenting wine was monitored with a data logger. It uses an optical gate to detect the passage of air. But the goal here was to combine bubble frequency with internal pressure measurements to calculate how much CO2 is being vented. Perhaps it would be possible to get an idea of how close the batch is to completion based on those calculations. A hole was drilled into the fermenter side of an airlock to take these pressure readings.
This actually works quite well during secondary fermentation when the bubble frequency is quite slow. The hardware is able to discern a pressure difference before and after a bubble has passed the lock. Unfortunately the system breaks down during the vigorous bubbling that takes place soon after pitching yeast. See a few bubble-counting clips in the video after the break.
Continue reading “Logging bubble frequency and pressure in your fermenter”
[Sebastian] is trying to improve the responsiveness of an electric keyboard. He was unsatisfied with the lack of adequate sensitivity to keystroke. The first step in his process was to measure how fast the quickest keystroke actually is. By setting up an LED and phototransistor and taking some measurements he found that sampling at 1 kHz would be more than adequate.
With initial testing complete he ordered some CNY70 transmissive/reflective light sensors that can be place below the keys. He measures the sensor with the ADC on an ATmega16 microcontroller. Running at 16 MHz he can sample each of the eight analog-to-digital converter channels at 1202 Hz. After doing a bunch of math he put together some lookup tables that are used to translate the ADC data into midi signals. We’ve embedded a video of one sensor controlling the midi program PianoTeq. [Sebastian] also sent us a schematic of one node in the sensor network (see it after the break).
When everything is said and done he plans to use eleven ATmega16 microcontrollers to address the 88 keys, with an additional microcontroller to act as the master using a two-wire interface for communications.
Update: [Sebastian] put up a webpage with a fairly verbose description. Reading it straight from the source really clears up a lot of questions.
Continue reading “Playing piano with optical sensors”