Re: ? on small battery operated fluorescents

On Feb 20, 9:55 pm, "Dave" <db5...@xxxxxxxxxxx> wrote:
<emailaddr...@xxxxxxxxxxxxx> wrote in message

news:1a613160-944e-47ea-8636-76abab39c34f@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

For some reason I'd thought you mentioned using 2 x AA cells while you
instead wrote 4.  Ignore the parts of my prior reply which were based
on that mistake.

No problem.  I hadn't thought about that being an older and less efficient
part (the fluorescent tube).  Would obviously rather work towards something
that
worked well.  That was just the best thing I found at the time.  Have since
found that the manufacturer of the parts used in that project is based in
the UK (I am in the US) and has recently been bought by someone else.
Nobody seems to be able to locate a transformer core or form, and the US
sales office doesn't answer their phone/hasn't replied to my email.  Also,
the
transistor called for is an obselete part for which there is no exact
substitute.  I could use the next part in line (tolerant of higher
emmitter/collector voltages etc.) but it's still not a late design.  Would
rather work with something more recent.

Recently found a couple of these at my local electronics candy store...

http://www.logical-lighting.com/pdf/LEDHPModuleWhitePDF.pdf

and built an emergency lantern out of them, using a couple of six-cell AA
holders and a 7812 voltage regulator.  It's not very impressive though, and
I was thinking of doing something similar with the two LEDs for the
flashlight and a fluorescent tube down the side, with a three-position
rocker switch to select which funcion is activated.  Would love it if
someonecould point me in the right direction for something like this.  Do
appreciate the help so far...

Dave

Unless you have a severe itch to proceed with local parts, I don't see
why you'd use that.
Also, I hate to see something running off battery power using a linear
regulator, unless this project is only about cheapest way with parts
you have on hand.

For a replacement to something that lasted 20 years, I think you
deserve more. As always, with a simple circuit homebrew product the
trickiest part isn't the parts as much as the case, what is reasonable
to use instead of being a chunky box when it comes to a flashlight
that has to satisfy a significant other.

You have not listed all your design requirements, so there isn't an
easy answer. One popular alternative among mountain biking circles is
to make the body of the flashlight out of tubular or square/
rectangular aluminum, then the body of the light becomes the heatsink
and the driver board, then for handheld use.. plus cells (battery) is
contained within. One caveat with this type of design is if the
handle is a heatsink, if it runs for a few minutes it starts to get
hot at higher current levels. Size becomes one of the design
criteria.

When it comes to implementing a driver board and LEDs, the sky is the
virtual limit on how you want to shoe-horn these into a finished
product if you only keep the cooling vs current requirements per light
output in mind. Basically, I suggest you try the modern Cree XR-E
LEDs, with a driver board that suits your average voltage for whatever
battery you want to use, then as far as the rest of the housing, it's
up to your imagination so long as you remember to keep the heatsinking
reasonable for the driving current used. More light requires a larger
flashlight, though all else being equal, the more LEDs you use, the
more investment in buying more per the light output you want, the
resultant lower drive current will reduce the size of the heatsink you
need since you reduce the heat density per LED. Driving XR-E's at
350MA per seems to be a sweet spot for good efficiency vs cost, but
this still requires at least a minimal heatsink.
.

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