brainwagon

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 […]

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 […]

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, […]

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.

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 […]

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 […]

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 […]

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 […]

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 […]

Of course I knew that all LEDs aren’t the same: they differ in color, size and brightness. They also differ in the forward voltage, reverse voltage and capacitance. When I simulated the Joule Thief with LTSpice, I just picked a random LED out of LTSpice’s catalog. When I simulated it, I got a waveform like […]

Kindred spirits Atdiy and whisk0r over at the tymkrs blog were playing around with inductors: They demonstrated that inductors can generative large inductive spikes: in spite of the fact that there coil is charged by a relatively low voltage, when you sharply disconnect a coil from a charging voltage, it generates a large voltage spike […]

I may have mentioned before, I’m kind of old. One measure of how old I am is the fact that I’ve actually programmed machines that used core memory. Real core memory. Little ferrite donuts on arrays of wires. Some time ago, I remember running across this awesome blog post from “Wayne’s Tinkering Page” which showed […]

I always think it is good to follow up a practical build of an electronic circuit with some simulation to try to learn some of the underlying design principles. LTSpice is a great circuit capture/simulation system which runs on Windows, but also runs pretty well under Wine. I was a bit intrigued by the behavior […]

I was bored, but not quite up to the challenge of debugging my existing radio project, or starting a new one. I idly began winding some wire onto a FT-37-43 toroid, and then remembered that I had never constructed a “Joule Thief”, a simple little circuit that allows you to light an LED using just […]

I’m old. I learned to program as a teenager in the 1980s. Back then, we learned to program on small microcomputers. These machines weren’t very powerful, but they had a neat feature: they were self-hosted. In recent years, a large variety of small microcontrollers have become popular. Many of these have capabilities far in excess […]