First off, it’s all about the lumens. Lumens are the visible light given off by a
source, and they are the ultimate goal. Wattage has often been confused with
lumens, thanks to how incandescent bulbs are rated (everyone knows that a
60W bulb is not as bright as a 100W one), but more efficient lighting technologies
have greatly changed the relationship between wattage (essentially
power usage) and lumens (light output). For example, an incandescent might
operate at about 12-15 lumens-per-watt (lm/W), while an LED bulb will be in
the range of 40-50, a much greater luminous efficacy...
The MintDuino is deceiving—this little tin of electronics is capable of providing
the brains for an unlimited number of devices limited only by your imagination…
and, of course, your bank account.
While the MintDuino is certainly capable of being used during a moment of
inspiration, you’ll find that the real power of the device comes when you sit
down, figure out what you want to make, and then start tackling your project
a bit at a time.
Serial Connection And Parallel Connection
Figure 1 shows the most basic and commonly used circuits for driving light-emitting diodes. In Figure 1(A), a constant voltage source (VCC ) is connected through a current limiting resistor (R) to an LED so that it is supplied with forward current (IF). The IF current flowing through the LED is expressed as IF = (V CC - VF)/R, providing a radiant flux proportional to the IF. The forward voltage (V F) of the LED is dependent on the value of IF, but it is approximated by a constant voltage when setting R. Figures 1(B) and...
Build a robot that responds to electrical activity in your brain—it’s easy and fun. If you’re familiar with Arduino and have basic mechanical building skills, this book will show you how to construct a robot that plays sounds, blinks lights, and reacts to signals from an affordable electroencephalography (EEG) headband. Concentrate and the robot will move. Focus more and it will go faster. Let your mind wander and the robot will slow down.
You’ll find complete instructions for building a simple robot chassis with servos, wheels, sensors, LEDs, and a speaker.
The phenomenon of total internal reﬂection, responsible for guiding of light in optical ﬁbers, has been known since 1854 . Although glass ﬁbers were made in the 1920s –, their use became practical only in the 1950s, when the use of a cladding layer led to considerable improvement in their guiding characteristics –. Before 1970, optical ﬁbers were used mainly for medical imaging over short distances . Their use for communication purposes was considered impractical because of high losses (∼ 1000 dB/km).
The role of the optical transmitter is to convert an electrical input signal into the corresponding optical signal and then launch it into the optical ﬁber serving as a communication channel. The major component of optical transmitters is an optical source. Fiber-optic communication systems often use semiconductor optical sources such as light-emitting diodes (LEDs) and semiconductor lasers because of several inherent advantages offered by them.
To our knowledge, only one previous effort (Wilson et al, 2007) explicitly studied
school travel in light of school choice. There, we found that school choice led to
longer school commute distances (because children attend schools across the district
rather than in their neighborhood) and reduced levels of walking and bicycling to
school (because longer commutes are less amenable to walking or bicycling). The
current study strengthens and expands earlier research.We survey parents to determine
attitudes that affect school choice and school travel mode.
In a similar vein, Azuri Technologies has focused its attention
on African villages that are too remote to have any connection to
an electric power grid. Azuri’s technology uses solar cells and the
latest lithium battery technology to run two powerful LED lights
for up to eight hours, eliminating the need for expensive kerosene
lamps. What makes Azuri unique is its business model. Instead of
selling the system, Azuri leases it at a cost that even poor villagers
can afford. The basic equipment is available for a nominal fee, and
the customer then leases time on it by purchasing...