Re: "Shake flashlight" how strong (current, volt)?
From: Don Klipstein (don_at_manx.misty.com)
Date: 06/19/04
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Date: Sat, 19 Jun 2004 06:40:29 +0000 (UTC)
In article <Xns9506E4FB2AB5heritagedestinations@212.83.64.210>, Lou wrote:
>Hello, I'm new to electronics. I want to make a small device with a small
>6V motor and no batteries. I want to use the "shake" system, which can be
>found in some fun flashlights. (see link: http://www.quality-items-
>flashlights.com/product_info.php?products_id=90 ).
>
>Only I am not sure how much power such a "shaker" can provide.
>
>I want to power a little fan with blades of say 12 centimetres wide
>(diametre, 5 inches), to make wind.
>
>I would appreciate it very much if someone could explain to me how much
>shaking you would need, to power the fan for about 3 minutes.
>
>And I would also like to know if I use "two" magnet shakers, do I increase
>the power 2 times? Or is there loss?
I would advise to use green LEDs having either peak or dominant
wavelength anywhere from 505 to 540 nm.
I would also advise that most such LEDs of "regular size" (5 mm AKA
T1-3/4, 3 mm AKA T1, smaller sizes, including similar smaller surface
mount packages, and even other sizes neither including a heatsink or a
"partial heatsink" nor requiring heatsinking, and questionable as to "high
flux" units in "spider" (4-lead) or "TopLed" packages or the like) tend to
have higher efficncy at lower currents, such as a few milliamps.
Blue, blue-green, white and green LEDs having rated current 350 mA or
more, in my experience, tend to have higher efficiency when somewhat
underpowered.
I would also advise charging of large capacitors for energy storage.
Along with lowest possible current through the LEDs from energy storage
capacitors, even if as low as a fraction of a milliamp. I would avvise
usage of blue-green or green LEDs having peak or (this i different)
dominant wavelengths anywhere around 500 to 540 nm.
I have found ability of LEDs having nominal wavelength close to 500 nm
being able to illuminate a whole room well enough for me to navigate by
using night vision even when said LED was fed 50 microamps and hyad at
this current a voltage drop of only about or maybe a little less than 3
volts.
Please consider "night vision advantages" of wavelengths in the upper
400's and lower 500's of nm, and also most LEDs having peak wavelength in
this range (and many other LEDs) having peak emissionn wavelength varying
a little notaceably slightly inversely with current.
Wavelength noticeably varying inversely with current I have found to
occur mainly with LED chip chemistries favoring higher efficiency at lower
currents. When the chip chemistry favors higher efficiency at higher
currents (a large majority of those with peak wavelength yellow-green 555
nm or longer, including most yelow, many orange, many red and a few
infrared chemistries), the peak wavelength in my experience tends to
vary less with current.
- Don Klipstein (don@misty.com, http://www.misty.com/~don/index.html)
- Next message: Robert C Monsen: "Re: Bad Idea: Put 9V Flasher LED on top of 9V Battery??"
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