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Constructing A Low-Power 2U Wireless Rack-Box
adelayde writes "Recently we decided to build ourselves a custom rack-mountable box that we could use as a web and DNS caching proxy and which would offer flexible wireless networking facilities and have an uniterruptible power supply. The result was a 2U rack-box with dual wireless networks built upon a low-power Via EPIA MiniITX motherboard. The box has two wireless networks built in with external antenna connectors, locking switches on the front to avoid tampering, a battery to give at least 20 mins of autonomous operation, a low wattage power supply and most importantly lots of blue LEDs :)"
I'm a college degreed Electrical Engineer with over 30 years of experience, including teaching electronics at the college level for three years. That regulator circuit looks quite familiar. As long as the heatsink is sufficient for the heat dissipation in the LM317, there should be no problem. Since this is powering only the wireless bridge, the current drain at 7 volts should be modest and it only needs to drop 5 volts across the regulator IC. The total power dissipation spread across both of the 1/2 watt resistors is only 85 milliwatts so no trouble there either.
If you are referring to the capacitor voltage ratings, the only requirement there is that the voltage rating of the cap be more than the voltage actually applied to it. For example a 35 volt cap is just fine with 6 volts across it. It could even be a 1,000 volt rated cap with no ill effects.
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
"Do the Right Thing. It will gratify some people and astound the rest." - Mark Twain
First of all, the human eye isn't the most sentitive to blue light, it much more sentitive to green. You can see the human eye's response curve here and a breakdown of color vs wavelength.
Secondly, the lumen or candela rating already takes this into account. At the peak of photopic vision, 555 nm (green), there are 683 lumens per watt. If you had one watt of blue light, it would only be about 100 lumens, because the human eye is less sensitive to that wavelength.
In other words, one watt of green light appears brighter than one watt of blue light, because humans are more sensitive to that color. One lumen of green light is just as bright as one lumen on blue light, because the lumen measurement takes this into account. That's the whole point of lumens, they are watts times luminous efficacy for human vision.