UtahNature has a few interesting emergency light project uses a few white LEDs to create an inexpensive light.
Project 1
Project 2
“We will describe constructing an emergency light using 3 or 4 white LEDs fitted into a 1/2 or 3/4 inch PVC pipe coupling and mounted into a clamp-on miniture light housing. Since most radio shacks have a 13.8 VDC emergency supply, we will configure the light to use this power source.
We tried making an LED light array with 3 white LEDs, then 4 white LEDs, but when we wanted even more light, we used 15 white LEDs.”
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Why did he put seperate resistors on each LED rather than doing them in series? Or at least
have 3 or 4 LEDs in series and have little series groups. That would be much more energy efficient.
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Hi David,
Only thing I can think would be for survivability of the circuit given a failure. Although we all know how reliable LEDs are and with a life of 100,000 hours this might not be the biggest concern.
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How is this better than a regular flashlight?
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Might not be better, but it would be more fun to build rather than buy 🙂
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We did this in March 2001, back when white LEDs were fairly new and expensive. We used current limiting resistors on each LED to make sure we didn’t burn any of them out. Of course, we quickly learned that LEDs are relatively hardy and could be wired in series without harming them.
The price decrease for LEDs and LED flashlights in the past 5 years has been amazing although not entirely unexpected.
This is truly a case where the follies of the past come back and bite you.
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Why cant the ckt be made more efficient by a charge pump ckt to drive the led chains off a low 4.5v battery that a flashlight has? can someone give a ckt idea for this?
I belive that the battery life will be much more that this. also the LEDs will glow more brighter.