Light Bulb, Diode, And Capacitor Step Mains Down To 12V DC

October 21, 2011 by Mike Szczys 64 Comments

[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.

Continue reading “Light Bulb, Diode, And Capacitor Step Mains Down To 12V DC” →

14-part RepRap Saga Draws To A Close

October 21, 2011 by Mike Szczys 17 Comments

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

October 21, 2011 by Mike Szczys 3 Comments

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

October 21, 2011 by Mike Szczys 12 Comments

[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

October 21, 2011 by Mike Szczys 5 Comments

[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 ~~mis~~use 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.

Continue reading “Illogical Voltage Double Uses Logic” →

Light Painting Nyan Cat With An Arduino

October 21, 2011 by Mike Szczys 5 Comments

You too can paint your favorite meme in light with just a few tools. [Skywodd] brought together a couple of different projects to make this happen. He had already built a large POV display and now uses a DSLR with long exposure to create light paintings (translated).

The Arduino-powered display is built from a strip of 35 RGB LEDs. Now, that’s four pins per LED but one of is ground, leaving just 105 pins that need to be addressable. A couple of things make this manageable. First, he etched his own circuit boards for the LED strips. This breaks out the contacts to the edge of the boards and simplifies the soldering a bit by taking care of the ground bus. Secondly, he’s using M5450 LED display drivers for addressing. After the break you can see the video of the prototype hardware (in French but blinky action starts at about 2:30).

If you’re looking for an easier way to do this, check out the light painting that uses manufactured LED strips.

Continue reading “Light Painting Nyan Cat With An Arduino” →

Grab Your Own Images From NOAA Weather Satellites

October 20, 2011 by Mike Szczys 55 Comments

Can you believe that [hpux735] pulled this satellite weather image down from one of the National Oceanic and Atmospheric Administration’s weather satellites using home equipment? It turns out that they’ve got three weather satellites in low earth orbit that pass overhead a few times a day. If you’ve got some homebrew hardware and post processing chops you can grab your own images from these weather satellites.

The first step is data acquisition. [hpux735] used a software defined radio receiver that he built from a kit. This makes us think back to the software-radio project that [Jeri Ellsworth] built using an FPGA–could that be adapted for this purpose? But we digress. To record the incoming data a Mac program called DSP Radio was used. Once you do capture an audio sample, you’ll need something to turn it into an image. It just so happens there’s a program specifically for weather image decoding called WXtoImg, and another which runs under Linux called WXAPT. Throw in a little post processing, Robert’s your mother’s brother, and you’ve got the image seen above.

[Hpux735] mentioned that he’s working on a post about the antenna he built for the project and has future plans for an automated system where he’ll have a webpage that always shows the most current image. We’re looking forward hearing about that.