brainwagon

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 […]

One year ago today, I first published a link to The Broadcaster Project, a site which had several tips on using command line tools such as ffmpeg to assemble videos. I use a similar technique to do my more recent videos: I take the raw footage from the camera and resize it, denoise it, and […]

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 […]

Dave, NM0S and designer of the HamCan, a kit that I previously assembled, but had some difficulty with nicely contacted me via email today so ask if he could be of help. I’m pretty sure that whatever the issue is, it’s my own fault, but hopefully with some patient help from Dave I can figure […]

I’m going to be nostalgic for a few moments. If you are too young to have any sense of nostalgia, skip ahead to the bold text below. You were warned! A few days ago, I mentioned that I was having a bit of flashback, thinking of my first experience with time sharing computers back in […]

Next weekend is our Maker Faire here in California, but there was just a Mini Maker Faire in Toronto, and it looked like there was some awesome stuff. Check out these neat video: Makers: Mini Maker Faire Toronto from Ryan Varga on Vimeo.

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 […]

In my previous post, I mentioned that I had programmed a machine that used core memory. It was the DEC 1091 we had at the University of Oregon back in the mid 1980s. I was overcome with a feeling of nostalgia, and decided to try to look up how to install TOPS-10 onto the simh […]

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 […]

So, over the weekend I assembled the HamCan, and got some pretty wonky performance. I’m going to go through it all again and see if I can figure out why the receive performance is so bizarre, (loose connection? poor adjustment?) but it got me thinking that part of the issue is that typical PCB construction […]