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>> 2nd law of termodimanics says nothing to you ? ?Not so quick. He may be freezing the bottles in his freezer in the kitchen and cooling a bedroom upstairs. That's no so unreasonable. Personally I would by a bag or block of ice from the grocery store.
>> Maybe an airlock to isolate the bedroom?Yes - we call it a door.
Downwind Faster Than The Wind Cart
Yup. I have used them that way as sensors for the light of a similar LED.
Dome LED's have a fairly wide variety of emission angles. This is generally controlled by how far they place the light emitter from the dome. The spec sheets almost always give you a "half-power angle" (the angle off-axis at which you're seeing only half the brightness). If you want a much wider emission angle you can cut the dome off with a dremel tool. If you care, you can then file or polish the end, but it's not necessary. The closer you cut it to the emission device, the wider angle you'll get. But be careful not to cut too close because there's a tiny wire in there that usually cannot be seen by eye.You'll find plenty of LED's here: http://www.ledsupply.com/
Nice instructable. You mention that IR LED's "generally works on a transmission frequency of 38KHz". This is generally true, but it's not in any way related to the LED itself. The designer modulates the LED as a way for the receiver to discriminate it from other IR sources. LED's are also modulated at very low frequencies to simply show a blinking LED, and are often modulated at relatively high frequencies with varying duty-cycle to effectively control their brightness. And then some are modulated at much higher frequencies to send data (as used in fiber optics for example).You also mentioned that "You can test a IR LED by viewing it under a Camera whilst a current is appliead across the LED. In other words cameras can detect IR rays emitted from the LED." This is true, but most cameras incorporate an IR block filter. Cameras that don't have an IR block filter can generally see near IR quite well (and tend to be cheap cameras and particularly security cameras). But it should be mentioned that even some cell phone cameras don't see IR LED's very well at all because of their IR block filter.
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