[ale] [OT]: one for the EE's...

[Keith R. Watson]

At 10:03 AM 4/7/2003 -0400, you wrote:


>   To stave off the fear of the dark I got two of those little push
>lights for my kids.  Blue with stars, moon and a space shuttle, they're
>pretty cool.  The only problem is the suckers will eat 4 AA batteries in
>a single night if left on.  When the kids wake up in the middle of the
>night and turn it back on, simply turning it off doesn't help.
>
>   Last night durring the thunderstorm I cut the end off a 5vold, 1amp
>power supply and soldered it to the battery leads.  It ran great for
>atleast 3 hours before I went to sleep (GFCI outlet) but was quite dead
>when we got up this morning.
>
>   I had used the 5volt as I figured I needed 6 volts (4xAA) and that was
>the closest, the next being 9.5volt.  As per the amperage I hoped it was
>within tollerances, but it was $4 for a new light if I was wrong (oh
>well).
>
>   Any suggestions on the Volt/Amperage power adapter I should look for
>when I go to wally world to replace this push light and get a proper
>power supply?  Ideally I'd rather not pay $4 for a light, $20 for a
>power supply (multi-voltage) that'll burn out overnight again.
>
>   The lights are actually pretty cool...
>
>Robert
>
>
>:wq!
>---------------------------------------------------------------------------
>Robert L. Harris                     | PGP Key ID: E344DA3B
>                                          @ x-hkp://pgp.mit.edu

Robert,

To do this correctly would require testing the max current draw of the 
bulb. Once you know this you can replace the battery with the correct power 
supply. However a simpler approach would be to get a larger 6 volt battery, 
such as a gell cell. Gell cells are commonly used in emergency lighting 
systems and uninterruptable power supplies. They come in all sizes 
depending on what length of runtime you need and they're rechargeable.

Another solution would be to use a light source that has a very low current 
draw. L.E.D. (light emitting diode) based lamps can provide the right 
amount of light for months on a battery. Here are a few examples.

This one plugs into an outlet. With the addition of an on off switch (like 
a cheap power strip from Home Depot) this would do what you want.

0.05 Watt LED Night Light
http://www.nolico.com/saveenergy/led_night_light.htm


This is an example of a flashlight that has an extraordinary run time on a 
single 9 volt battery.

PALight
http://www.gadgetguys.com/readreview.asp?ArticleID=53
http://www.theenergyalternative.com/catalog/?item=108


Another possibility would be to back fit your existing night light to use 
an LED. Here's is an example.

http://www.zetatalk.com/info/tinfo20v.htm


I once saw an LED flash light that would run continuously for 3 months on a 
couple of D cell batteries.

I haven't used any of the devices mentioned above but it gives you an idea 
of what is possible using LEDs. You may want to look around and see if you 
can find something that meets your needs.

keith
-------------

Keith R. Watson                        GTRI/ITD
Systems Support Specialist III         Georgia Tech Research Institute
keith.watson at gtri.gatech.edu           Atlanta, GA  30332-0816
404-894-0836

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