Archive for month: May, 2011

Lotte Reiniger’s Adventures of Prince Achmed

May 30, 2011 | Movies | By: Mark VandeWettering

Today, while scanning around for things that I could watch on Netflix streaming, I found that they had The Adventures of Prince Achmed, which was a movie which I had heard about, but had never seen. Wikipedia claims that it is the oldest surviving full length animated feature film, dating back to 1926. I first […]

Speleogroup’s cool LED headlamp design

May 29, 2011 | diy, electronics, My Projects | By: Mark VandeWettering

Fellow hacker Mike Cowlishaw tweeted me a reminder that he had worked on a design for a spelunker’s headlamp that used Luxeon LEDs, and had excellent high performance. I remember that I listened to a talk about this design, but at the time, I wasn’t saavy enough in electronics to grasp the details, and it […]

A simple constant current LED circuit

May 28, 2011 | diy, electronics | By: Mark VandeWettering

I’ve been pretty happy with the performance of my linear current based LED transmitter, but that was just sitting on the bench, driving a 20ma device. As I played with the circuit, I began to realize that if I scaled the circuit up to a 1W LED, its deficiencies in terms of efficiency would become […]

High Power LED Driver Circuits

May 28, 2011 | diy, electronics, My Projects | By: Mark VandeWettering

My recent experiments with light based communication left me thinking about simple circuits for driving LEDs. I’ve got three big LEDs (1W) on order from deal extreme, so I was looking for circuits to drive these larger LEDs. This Instructable has some good ideas. I’ll probably breadboard some of these soon. High Power LED Driver […]

Return Infinity – BareMetal OS

May 28, 2011 | Computer Science, Operating Systems | By: Mark VandeWettering

At various times, I’ve been interested in writing operating systems. I haven’t done much thinking about this recently, but it is a topic of interest. I hadn’t seen this project before: a small 64 bit kernel written in assembly. I have no idea whether it’s interesting, but I thought I’d bookmark it for future investigation. […]

FUNcube Dongle on order!

May 26, 2011 | Amateur Radio | By: Mark VandeWettering

Huzzah! I’ve been wanting to get a Funcube Dongle Pro for some time, but they have been in short supply. Today, a fresh batch went on order, and this time: success!! The Funcube Dongle Pro is a cool little software defined radio that plugs a USB port, and receives from 64Mhz to 1700Mhz. I am […]

Question about LEDs…

May 23, 2011 | electronics, My Projects | By: Mark VandeWettering

A few days ago, I posted a query to twitter regarding voltage drop in LEDs: I didn’t receive a lot of truly helpful replies: a few people reinforced the general dogma that indeed LEDs were diodes, and since they were diodes, they should have relatively constant voltage drop despite current across them. But that’s not […]

More light transmitter experimentation…

May 21, 2011 | Amateur Radio, electronics, My Projects | By: Mark VandeWettering

Today, I had to do some yardwork, so I dusted off the weed whacker, and climbed the back of the hill to chop down some high grass. At the end of an hour, I was about 40% done (I’ll do the rest next weekend) but sneezing and coughing from the liberated pollen and dust. So, […]

Improved Joule Thief Circuit

May 20, 2011 | electronics | By: Mark VandeWettering

While surfing for more LED information, I found this rather nifty little circuit on Electronic Design’s website. It’s a little Joule Thief-like circuit, but with enhanced efficiency (~80%) and it can drive white LEDs with rather large forward voltage drops. Archived for later…. Single Alkaline Battery Drives White LED.

DIY FET/home-made transistor Scientific American June 1970

May 20, 2011 | Amateur Science, electronics | By: Mark VandeWettering

When I was still in grade school, I (and this will be a shock to my readers) spent a lot of time in libraries. Our library used to have a free bin, where they would toss things that they no longer wanted in their collection. One day, I came by and found a pile of […]

A foxhole radio…

May 20, 2011 | Link of the Day | By: Mark VandeWettering

IRC and Minecraft buddies Atdiy and whisk0r have been doing some cool videos on making cigar box guitars, some kind of neural network stuff, and more recently: some introductory electronics videos. After winding inductors and making their own capacitors in previous episodes, they get around to making their own foxhole radio just using a blued […]

LED Transmitter Schematic

May 20, 2011 | electronics | By: Mark VandeWettering

Okay, so here’s the schematic for the LED transmitter circuit as I assembled this evening. I tried to write up an exposition of how it works, but frankly, it pales in comparison to the clarity and completeness of KA7OEI’s page. But here’s the basic idea: imagine that you supplied 1V to the input of the […]

An improved linear current LED transmitter

May 19, 2011 | electronics, My Projects | By: Mark VandeWettering

I spent some time reading KA7OEI’s great article on creating a good linear current driver for an LED or laser based communication system. The basic idea was pretty straightforward, so I decided to try it out when I got home. The “simple” circuit that I had before was in no sense linear: the audio became […]

KA7OEI – LED Linear Current Modulator

May 19, 2011 | Amateur Radio, electronics | By: Mark VandeWettering

My silly experiment with an LED communicator naturally led me to looking up more complex (and better engineered) versions of the same kind of circuit. There are now cheap LEDs that can emit a watt or more of energy, and produce a prodigious amount of light. It seems like an area which is ripe for […]

A simple LED transmitter, and LED receiver!

May 18, 2011 | electronics, My Projects | By: Mark VandeWettering

Tonight’s 20 minute electronics project was to create a simple transmitter to send music using light. A trivial circuit modulates the current through an LED, and a different LED serves as an (inefficient, and not very good) light sensor. Normally you’d use a selenium photocell or the like, but I couldn’t find one in my […]