LED Help

Hi
I need some advice on how to go about lighting up a picture made from
stained glass. The frame is approximately 24" x 24" (600mm x 600mm) and the
actual glass is 20" x 20" (500mm x 500mm)

I want to make up a frame approx. 1" (25mm) thick to sit behind the picture
frame. Within this I want to insert some white LED's to light the picture
from behind.

I need help on how many I would need, where would be the best place to
source what I need (in the UK), what I will need (LED, resistors
transformers?) and some ideas on mounting the LED's. Also, what sort of life
would I get from batteries, maybe a couple of AA ones? I'd hate to have to
start channelling walls to run power to it!

Lots of questions but I would appreciate any help.

TJ

 

Lets see first you will need to know the max ammount of current that
the LED can operate then depending on that current and the voltage(ex 2
AA = 3v) you are going to use calculate the resistance needed in the
circuit using ohms law where R=V/I then conect the positive of the
battery to a switch so you can turn it on and off then conectt it to
the resistor then to the LED then to the negative of the battery
i guess that would be all

 

If possible, I'd suggest some kind of wall adapter.

5 white LEDs would probably be sufficient; having them shine backwards
onto a white piece of paper might work well.

You can get very bright LEDs from lots of places, but here is a selection:

http://www.goldmine-elec-products.com/products.asp?dept=1207

You can also get the wall-adapter there...

These white LEDs usually have a 'forward voltage' of between 3 and 4
volts. So, if you get a 5V adapter and a few 100 ohm resistors, you can
hook them up in parallel (view with 'fixed point' font).

5V--o----o----o----o----o
| | | | |
100 100 100 100 100
| | | | |
--- --- --- --- ---
\ / \ / \ / \ / \ /
--- --- --- --- ---
| | | | |
| | | | |
0V--o----o----o----o----o

This will give you (5-3.4)/100 = 16mA through the LEDs, which should
be sufficient to make them light up nicely.

If you just can't use a wall-adapter, 3 D cells might give you adequate
voltage for a couple of weeks.

--
Regards,
Bob Monsen

I know not with what weapons World War III will be fought, but World
War IV will be fought with sticks and stones.
Albert Einstein