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Cool Gadgets, Gizmos, Games and Weird Science

Cool Gadgets, Gizmos, Games and Weird Science

Electronics - www.vetco.net Switch 6. Transistor as a switch Resemble circuit between the transistor and switch (fig.6a) typical transistor interface, as a switch. (fig.6b) switch interface function resembling fig a. (fig.6c) opto-coupler interface. (fig.6d) resembling opto-coupler interface, compare fig c. Using transistor as a switch to drive high current loads (fig.6e) Digital Logic interface to a Relay as output using transistor. - npn transistor "BC549" to drive up to 0.1A load - npn transistor "2N3019" to drive up to 1A load - npn transistor "tip31a" to drive up to 3A load (fig.6f) same transistor setup to drive a motor. The switching setup to drive the coil load On/Off, can generate "back emf". (fig.6g) flyback diode typically 1N4148 (for small current rating), to eliminate back emf generated. Analog Devices, IRF (International Rectifier), MAXIM, National Semiconductor A switch is a mechanical to electrical conversion device. Transistor can be used as a switch or as an amplifier. More information

Korben - Site d'actualité geek et tech TechFresh, Consumer Electronics Guide Motherboards.org | The Latest News, Reviews, Guides and Rankings for Motherboards and PC Hardware. The illustrated guide to a Ph.D. Imagine a circle that contains all of human knowledge: By the time you finish elementary school, you know a little: By the time you finish high school, you know a bit more: With a bachelor's degree, you gain a specialty: A master's degree deepens that specialty: Reading research papers takes you to the edge of human knowledge: Once you're at the boundary, you focus: You push at the boundary for a few years: Until one day, the boundary gives way: And, that dent you've made is called a Ph.D Of course, the world looks different to you now: So, don't forget the bigger picture: Keep pushing. There's a bit more below, but I also wrote a follow-up 5 years after the illustrated guide which may be of interest -- HOWTO: Get tenure. Related posts If you like these posts, then I recommend the book A PhD Is Not Enough Get it in print; fund students; save lives By request, a print version of The Illustrated Guide to a Ph.D. is on sale. Click here to preview or buy it. Why biology? License: Creative Commons Resources

Mobile Trendy Gadget Surviving a traffic surge: Three techniques to scale your site fast My server I've been a satisfied linode customer for about seven years. I've always had the cheapest plan (about $200/year), and because it's a virtual server, it automatically upgrades for free whenever the cheapest plan gets more memory, disk space or bandwidth. Right now, that means 512 MB RAM, 24 GB disk and 200 GB/month bandwidth. Step -1: Detect the surge I keep tabs on my site through an app for Google Analytics on the iPhone. Unfortunately, Google Analytics failed to detect the surge: page load time was so high that visitors were closing the page before analytics could load. As a result, my analytics showed almost no increase in page views. It took me about fifteen hours to realize my site was crushed. I now have a cron job running to watch for stress on might.net. It looks at the httpd log file every five minutes, and it sends me email when requests per second exceed a preset threshold. I also installed the linode iPhone app, so I can check server load in real time. More resources

Blog Web 2.0, Buzz, Technologies et Gadgets Holycool.net 7th Grader mimics Nature 13 year old copies Nature to Improve Solar Performance Thirteen year old Aidan Dwyer was walking in the woods in Upstate New York in the winter and noticed a spiral pattern to tree branches. Aidan realized the tree branches and leaves had a mathematical spiral pattern that could be shown as a fraction. After some research he also realized the mathematical fractions were the same numbers as the Fibonacci sequence. "On the oak tree, the Fibonacci fraction is 2/5, which means that the spiral takes five branches to spiral two times around the trunk to complete one pattern. Aidan's backyard in Northport, NY. The 7th grader next wondered why nature used such a pattern? Aidan discovered that the Fibonacci pattern helps deciduous trees, in higher latitudes, efficiently track the Sun and collect the most sunlight even in the thickest forest, on the cloudiest days. The American Museum of Natural History has awarded Aidan a Young Naturalist Award for 2011. Share this page... Got water?

Emilie Ogez - Pérégrinations d'une fan du web OhGizmo!

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