In response to the nasty criticism about this being so very dangerous. Most of the readers drive cars, which are far more dangerous than this flashlight. Almost everything requires a bit of wisdom and good judgement to use. The safety rules designed to protect drunks bent on self destruction are a needless burden on most of society. What I am referencing is the european safety regulations for electrical equipment, by the way.
At some point an individual must take responsibility for the results of their actions, and a big part of that responsibility is understanding what one is doing. I know that is offensive to those who abhor personal responsibility, go ahead and be offended.
Those who produce my designs are confident in my level of responsibility, and know that I will not deliver a design that will not meet the project requirements. That would be a big risk if I were not responsible enough to assure that the design was adequate. Certainly there are many other engineers in a similar position, who are responsible for doing their job correctly. Those are the good engineers, the others need to have fifty people check their work for errors, oversights, and other types of goof-ups.
I disagree with the statement that Gadget Freak articles are just for novices. I'm a retired electrical engineer and I don't miss a single one. Even an experienced engineer can sometimes learn something.
For the most part, it is eye-safe. I wear sunglasses for the final test, and welding goggles while building becasue I am right next to the lights. More than a foot or so away, and it's not very dangerous for a short glance. Only when you are RIGHT on the LEDs does it really start to cause damage (I used a light-sensitive resistor and the threshold of a 3mW laser to determine what would cause eye damage).
Basically, if you don't have something right in front of the LEDs, and no one is looking directly at it, it isn't dangerous.
First off let me give John a thumbs up for the good work.
I have been reading this article over and over and cannot understand how Design News publishes a project that falls into a category of a flash light that can cause eye damage if looked at accidentally. This is not a novice project and Design News should considered not publishing projects of this type.
Nice project;it's great to see this lad working hands-on on this project. Perhaps a good follow-on project would be to design a switching regulator and avoid the power loss in the resistor bank. Keep up the the good work you've started.
My humble apologies. I just cranked through the numbers (Using E^2/R, 90W across 1-ohm means voltage of ~9.48V, and current of ~9.48V; break that into thirds, carry the zero, hold yer tongue right, etc...) and John (along with the rest of you) is correct! Somehow, 30 years as a BSEE and all, I let my mind take over before doing the (full) analysis.
The first Tacoma Narrows Bridge was a Washington State suspension bridge that opened in 1940 and spanned the Tacoma Narrows strait of Puget Sound between Tacoma and the Kitsap Peninsula. It opened to traffic on July 1, 1940, and dramatically collapsed into Puget Sound on November 7, just four months after it opened.
Noting that we now live in an era of “confusion and ill-conceived stuff,” Ammunition design studio founder Robert Brunner, speaking at Gigaom Roadmap, said that by adding connectivity to everything and its mother, we aren't necessarily doing ourselves any favors, with many ‘things’ just fine in their unconnected state.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.