Alright, this is something I’ve been meaning to upload for a while. It’s the schematic for a decent linear power supply. It addresses the limitations of just using a variable linear regulator, but it has many of the same draw backs in it’s design. In addition to a connector for output power, I added two linear 0-5V outputs for measuring output voltage and current with an ADC. I’ll hook it up to an Arduino this weekend to see how well that works. When I get a chance, I’ll upload the .sch file for the schematic, but I still haven’t chosen actual parts yet. Maybe I’ll even put together a .brd file. We’ll see. I’ll try to get a brief write up of the design online later this weekend.
This photo is of the Z Machine – a device designed for X Ray experimentation. The device works by compressing plasma under an intense magnetic field. In order to generate this giant magnetic field, tens of millions of amps are dumped across a network of small wires, which also completely obliterates them. The system is insulated by a container of deionized water and another container of transformer oil, but even still, the magnetic field is large enough and changes so fast that currents are generated in any metallic object near by creating the giant arcs seen in the photo above along the surface of the insulators. The machine pulses the current for 100 nanoseconds, and consumes 50 terawatts of power. The device is used to study a lot of high energy physics, such as fusion, but I imagine that this technology will eventually find itself in to the secret under ground laboratory of mad scientists all over the world, so look out James Bond.
So what was once just an optics debate has now entered in to the main stream media. Lumens vs. Watts, what should we be using to rate our light bulbs? The short answer – lumens. This has been the real unit of measurements that people in the lighting industry have been using for years, so in many ways, the debate ended long ago, but now that CFL and LED technology are being used in general lighting, it’s going to take some time to convince people to start using it.
The reason that we should convert over to lumens in the first place is that the unit Watts actually doesn’t describe light. It describes real power (technical side note, the unit is volt amps (VA) for power with an imaginary component). From an electrical standpoint, this means the combination of voltage and current. This means that when you hook up a 60 watt light bulb to your house wiring, you’re going to consume an additional 60 watts of power. The problem is that this doesn’t describe how that power is being used. Ideally, all this power should be producing visible light, but the vast majority of that power is going outside the visible spectrum in the form of heat in the infrared range as the temperature of the filament reaches thousands of degrees. That’s not good, we don’t care about thermal radiation – we only want light. Well, since ever since the first light bulb rolled out of Edison’s lab, we have been using the same 120VAC supply, and since incandescent bulbs all have about the same efficiency (light output per watt, that is), we could effectively describe how bright a bulb was by how many watts it was consuming. Fast forward a hundred years of this, and people no longer differentiate between power consumed and light output.
Then comes the LED. An LED can easily put out five times more light for the same amount of power as an incandescent bulb without even running the LED at it’s most efficient current level. This is because LEDs don’t need to get up to high temperatures in order to operate. In fact, most LEDs want to stay around room temperature, hence the giant heat sinks. This means more light output for the same power input, so if an LED were to run at 60 Watts, it would be uncomfortably bright (it would be about a 300 Watt incandescent, yowch). So this has led to a trend of LED general lighting manufacturers to light their wattage equivalence. This is complete bologna. You can’t say 12 Watts is equivalent to 60 Watts. That sentence doesn’t make any sense. What they mean to say is that the lumen output is the equivalent. Lumens describe the total light output of a source that can be detected by the human eye (as opposed to radiant flux – the total light output of a source).
While people may not want to go back to school to learn how light should be properly measured, there needs to be an effort to correct this bad habit of using the wrong unit of measurement. Perhaps people are comfortable with Watts because other objects are also listed in Watts such as microwaves, hair dryers, and speakers. Besides, we can then add up this wattage to describe how many things can be hooked up to the same circuit breaker. That’s handy, right? So in reality we shouldn’t stop listing the wattage of light bulbs, but instead list the lumens, the wattage, and a brief description of the difference so consumers see on their own how much power they could be saving by using alternative lighting technology.
So I know everyone has their own opinion about the OWS protests right now, so I don’t want to talk about whether or not I agree with their message, but one thing that I’m kind of surprised about is that no one is protesting for IP law reform. Where banking reform is something people tend to go back and forth over, everyone I’ve ever talked to in the tech industry has agreed that the US patent system needs some fine tuning, yet this problem gets very little main stream coverage. I was pretty thrilled when I noticed that This American Life covered the story a while back. They did a marvelous job sumarizing the problem, and it’s definitely worth the listen. Besides, TAL is an amazing program, and if you aren’t listening to it already, you really should start.
Okay, I work in the LED industry so I’m a little biased, but LEDs really aren’t getting the reputation or news coverage they deserve. Yeah, CFLs are cheaper, and incandescent are easier to dim, but LEDs are to either of these as the microprocessor was to the vacuum tube. The real advantage of LED technology, once you get past the energy savings, of course, is how much more an LED can do.
What I mean is that an LED light bulb in the future won’t just be sitting plugged in outlet like your current light bulb. It will have smart electronics in to it. This means that any lightbulb could function as a smoke alarm, a motion detector, an embedded speaker, a wireless hub, or any other million possibilities. Imagine a future where LEDs can tell you when they burn out or need replacing wirelessly, either through text message or email. Incandescent and CFL bulbs are naturally incompatible with this technology. Incandescent bulbs were designed to operate on a standard set about a hundred years ago, 120VAC at 60 Hz, so besides being naturally inefficient pieces of technology, they also require far more voltage than what most electronic devices are designed for. By comparison, all the electronics in a car is designed to operate at no more than 12VDC, one tenth the voltage (let’s forget about the difference between AC and DC for just a second). CFLs are not really any different. While they take an input voltage of 120VAC, this is actually being converted internally by a ballast or flyback converter (to get technical), usually up to around 1000VDC necessary to excite the gas inside the tube.
LED bulbs, on the other hand, are usually made up of a train of smaller LED die, each one operating between ~2.5-5VDC depending on material and wavelength, among other things. As an example, let’s take a train of blue LEDs. If you hook them up in series, and run 700mA through them, you’ll see a voltage drop of about 12V. This is great, because this is close to the voltage requirements of most modern electronics. This means that things like speakers and alarms can run straight off this voltage. Even things like microprocessors can be run if hooked up to a linear regulator. Good luck getting a linear regulator that can go from 120VAC to 3VDC. This opens up a lot of possibilities. The brightness of the LEDs can be played with by adjusting the number of LEDs in the string, or by running several strings of LEDs together in parallel.
Of course, that’s not to say LED technology doesn’t have it’s draw backs. Unfortunately, wiring standards are still designed for ancient technology, so we’re stuck with 120VAC. This means that LEDs require complicated hardware to regulate the output. This also makes dimming of LEDs a hot topic right now in the design world – how do we get LED technology to work with standard dimmer switches. All of these problems are just design puzzles that will be worked out in the future as LED technology continues to grow and become more common place in general illumination.
Added a few photos, finally. Expect more photos to be added soon.
So I’ve signed up for the intro to Databases course being done through Stanford. As a study aid for people taking the course, I’ve decided to post my assignments online as a reference. These will be posted under the projects section. Also, resume section is updated with links to social media sites.
UPDATE: Due to time constraints, I will not actually be able to take this course. Oh well, always next year!