# Light bulb, diode, and capacitor step mains down to 12V DC

[Todd Harrison] needed a way to run a 12 volt PC fan from mains voltage. Well, we think he really just needed something to keep him occupied on a Sunday, but that’s beside the point. He shows us how he did this in a non-traditional way by using the resistive load of an incandescent light bulb, a diode, and a capacitor to convert voltage to what he needed. You can read his article, or settle in for the thirty-five minute video after the break where he explains his circuit.

The concept here is fairly simple. The diode acts as a half-wave rectifier by preventing the negative trough of the alternating current from passing into his circuit. The positive peaks of the electricity travel through the light bulb, which knocks down the voltage to a usable level. Finally, the capacitor fills the gaps where the negative current of the AC used to be, providing direct current to the fan. It’s easy to follow but the we needed some help with the math for calculating the correct lightbulb to use to get our desired output current.

# Hydrocrystallophone probably won’t make you insane

[Fish] is really proud of his newest creation, the Hydrocrystallophone. This new instrument reminds us of an even more steampunk version of [Benny Franklin]’s glass armonica – an instrument that reportedly plunged the player into a, “dark and melancholy mood.”

The build is based around a 1920s hand-cranked phonograph motor. The phonograph motor spins a wine glass filled with water. The water level (and thus tone produced by the wine glass) is varied by a brass tube inside the glass connected to a hydraulic cylinder. Pushing and pushing on the handle of the hydraulic cylinder causes the water level in the glass to change.

We’ve all seen wine glass music before, but this is the first time we’ve seen it with just one glass. [Fish] is working on modifying the phonograph’s governor to get rid of the effects of 78 RPM on the water. He hasn’t quite mastered his new musical invention yet, but we can’t wait to see what [Fish] is able to play with some practice.

In case you’re keeping track of the musical instruments featured on Hack A Day that fall into the “why didn’t I think of that” bin, The Hydrocrystallophone would be the second such instrument in as many months. It’s a very simple but really ingenious device. Check out the video of the Hydrocrystallophone after the break.

# Going for the amateur balloon altitude record

At 11 AM London time, October 22, the Sutton grammar school for boys is going to be launching Apex Alpha, a high altitude amateur balloon for an attempt at the UK altitude record. Unlike a few other balloons we’ve seen, the Apex team is doing it right and giving everyone the downlink details for the balloon.

The payload for the balloon was built entirely by student of the Sutton grammar school and weighs less than 300 grams. While it’s not carrying a camera for the all-important pretty pictures, the payload does have a GPS module and a transmitter; it’s just enough to do the required testing on the lead up to Apex III.

Right now, the UK amateur balloon record stands shy of 130,000 feet. The team gained a lot of experience with their Apex I and Apex II launches, and they’re pretty confident they have the experience to pull this one off. You can check out the progress of the Apex Alpha flight on the spacenear.us tracker. For us Yanks, the launch should start October 22nd at 6:00 am Eastern time and 3:00 in the morning for the West coast. The team says they’ll be updating that throughout the flight.

UPDATE: Apex Alpha just won’t burst. Any HAMs near Berlin in Eastern Europe are sorely needed. Head over to the IRC chat if you can help.

# 14-part RepRap Saga draws to a close

Behold, another RepRap springs into existence! Well, springs might not be the best choice of words, it took a while and there were many bumps in the road. But [NBitWonder’s] self-built RepRap is now finished and you can read his 14-part build log to see all that went into the process.

We checked in on the project at one of the early stages. At that point he was just beginning to assemble the hardware and we mused that the calibration stage is where we thought things would get exciting. The project didn’t disappoint, as he had many follies getting the extruder heads to work. At first some issues popped up when figuring out what diameter filament would work for the print head he was using. Once that was worked out, a less-than-precise PID controller led to the clogging and eventual destruction of the extruder tip. He goes on to assemble and test a heated build platform only to discover that the resistors shipped with the hardware are shockingly underrated for the task. We could go on and on, but that would ruin the fun for you. Bookmark this one for the weekend and enjoy!

# Extend your personal weather station’s reporting capabilities

This Nexus wireless weather station has an array of weather sensors that you mount outside and monitor on the LCD screen. It also has the ability to stream the data over USB, but that feature is only supported in Windows and the companion software leaves a lot to be desired. Here’s a technique that will let you unlock the potential of the data by streaming it to your Linux box or directly to the Internet.

It turns out that grabbing the data via Linux has been made quite easy thanks to a package called TE923 (translated). With the base unit connected via USB, the software will pull down a string of colon-separated data which will be easy to parse using your favorite scripting language. But what if you don’t want to tether this to a computer?

The project goes one step further by using a Carambola board. This is a WiFi board with a USB port on it. It runs OpenWRT so getting TE923 going is as simple as building the package. The best part is, any wireless router that runs OpenWRT (or DD-WRT, etc.) and has a USB port can substitute for this board. With the module connected to the station, data is pushed to the Pachube website to serve as a custom web readout.

[Thanks Saulius]

# Building optical flex sensors

[Joel] dug up this hack that he pulled off over ten years ago. It’s inspired by the Nintendo PowerGlove, and uses flex sensors to react to movements of your fingers. The interesting thing is, he built these optical flex sensors himself.

He likes to say that this is a ghetto fiber-optic setup. The inlaid diagram above gives you an idea of how the sensors work. An IR LED and infrared diode are positioned at either end of a piece of clear aquarium tubing. When the tube is flexed, the amount of light that makes it to the diode is diminished, a change that can be measured by a microcontroller. [Joel] found that he could increase the resolution of the sensor by adding something to the center of the tube, blocking the light when not straight. In this case he used pieces of scrap wire. The outside of the sensor was also wrapped in shrink tubing to keep ambient light from interfering with measurements.

He uses a trimpot to tune the sensors but we wonder how hard it would be to add a calibration algorithm to the firmware?

# Illogical voltage double uses logic

[Jonathan Thomson] just finished writing up his entry for the 7400 logic contest. It’s a voltage doubler that uses a 74HC14 logic chip. Because this is not at all what the chip was meant for–and he’s a sucker for puns–he’s calling it the Illogical Dickson Doubler.

What he’s got here is basically a charge pump built from a set of diodes and capacitors. On the breadboard you see two chips, one is used as a clock signal generator for the other which is acting as part of the charge pump. We’ve seen a string of hacks that misuse the protection diodes on the inputs of logic chips. In fact, [Jonathan’s] setup uses the same back power concept that barebones PIC RFID tag did. You may remember in that project the chip was being powered from one of the I/O pins, with the VCC pin not connected to anything.

We’ve embedded a video after the break with shows some voltage measurements, as well as an LED being powered from the doubling circuit.