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G8MNY  > TECH     10.05.23 09:12z 95 Lines 3958 Bytes #8 (0) @ WW
BID : 47094_GB7CIP
Read: GUEST
Subj: Cheap Battery/12v LED Light
Path: SP7YDD<SR1BSZ<IW0QNL<ON0AR<GB7CIP
Sent: 230510/0907Z @:GB7CIP.#32.GBR.EURO #:47094 [Caterham Surrey GBR]
From: G8MNY@GB7CIP.#32.GBR.EURO
To  : TECH@WW

By G8MNY                              (Updated Aug 13)
(8 Bit ASCII graphics use code page 437 or 850, Terminal Font)

Recently I discovered the "99p shop" and "Poundland" discount shops are still
selling twin packs of 4.5V self contained 3 LED battery lights for 99p
(~1.5eu/$). Is this less than parts cost? I have seen these lamps in 3 packs
for far more in other shops!

Inside there is a proper locking "tack" switch, 3 bright LEDs, 10R, flexible
reflecting housing button spring, & stick up 3x AAA in the round battery box.

     clear press cover
       _..----.._              n  = LED
 /~~~~             ~~~~\        
 ~\.n./~~\.n./~ Ĵ
(bat)________(bat)      ~\. = Spring Reflector
|.......................|
===========================         = Switch
Bernet   ~~~~~~~~~~              
 Base      Sticky                ___ = PCB

White LEDs are about 3.5V, so a 10R is in series with a 3 paralleled LEDs on
4.5V to limit the current.

+o\o10RĿ
__                     
__            __  __  __
__ 3x    LED \_/  \_/  \_/
   AAA                 
                       
 

The lights are quite useful as they are. They draw some 90mA from the 3x AAA
cells. But I found the double sided sticky quite poor. So I intend to screw the
base in place & attach the body.

MODIFICATION FOR 12V & EMERGENCY LIGHTING.
This is a fiddly job! The case is lightly glued around the edge and a small
screw driver/knife inserted between the cover and black inner and carefully
worked around will crack the glue, and separate 2 undamaged parts.

Putting the LEDs in series is done by tuning the middle one around & cutting 2
of the paralleling PCB tracks. Then remove the 10R and add a 150R to the -ve
lead. This will then give about the 25mA @ 13.8V. And by putting a diode input
after the switch, an Emergency lighting option can be added. Many of these low
power lights can easily be run from a floated battery on mains with a mains
fail relay.

             1N4001
Emergency oĴ>Ŀ
Lights +                                      ___    ~-_ 
            o\oĿ      E [o o]>ô(:)~-_ PCB
                        Ŀ  Ŀ           ] [          ~-_
     +12V o           __  __  __   +12V[o o]Ĵ  SW (:) >
                   LED \_/  \_/  \_/        ] [          _-~
                                  0V [o o]150(:)_-~
       0V o150                     ~~~    _-~

To makes room for a small 3 way block connection, with a soldering iron I
perforated and cut a hole in the middle of on of the AAA battery holders, to
suit the connector. With care the 3 holes for the bernet mounting plate still
work. The PCB is held firmly back in place on the cut battery mount with heat
glue and the lamp tested, then the whole lot is glued back together.

Running permanently these LEDs light have a short life, as the get quite a bit
dimmer after 6 months on!

MAP LIGHT
Using some strip board pressed into the chrome holder, I replaced a hot dim
power hungry lensed lamp with 6 LEDs. I cut away the copper track away at the
edge to make sure there was no shorting to the case.
__________________       _____________________
Ŀ                  Ŀ 
   (o)_.--'''~~\         (o)_.--'''~~             o o  6 LEDs
   (_)_/\/\/Bulb   |        (_)_  Rs   ||LEDS          o   o
       ~---...__/             ~---...__             o o

As this is used for illuminating my radio while /M (14V battery), I used 2 120R
as the series Rs, one for each chain of 3 LEDs.

12V SAFETY
Make sure the 12V is fused (e.g. 1A) & there is no fire risk from trapped wires
etc.

If your find the light is too directional, just lightly scratch LED lens heads
or lamp cover to defuse more of the light.


Why Don't U send an interesting bul?

73 de John G8MNY @ GB7CIP


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