[Dirty]

So, im bored.
i just got a new dining table with a frosted glass insert on the top.

I thought it would be cool to create a string of LEDs to mount under the glass and illuminate it from below.
I know i could just go buy a string of christmas lights or whatever, but i dont want a cord coming out from the table.
So i'd really like to have a self contained unit that mounts below the table and runs off batteries.

But heres the problem.
I have a basic understanding of electrical wiring or whatever, and i was planning on just running them all in parrallel.
I know how to figure out the resistor i would need and everything based on the type of LED and the power source.
but heres the question.
Would i be able to get away with running just one resisitor at the beginning of the circuit between the battery and the LEDs, or would i need to run a resistor after each LED?

I was scanning the web and some people said that batches of LEDs can have different resistance, and so you may run into a case where if you run them in parrallel, one may burn out and then the rest all are overloaded with the extra current, and all burn out as well.

Having to put a resistor with each LED would just be a pain...so id like to try and avoid that...

Also, how many LEDs do you think would suffice? the tables about 55x30

 

[ALEXIS_DH]

http://ourworld.compuserve.com/homepages/Bill_Bowden/led.htm

one resistor seems to be enough.
you´ll need a lot of leds for a table that big, one failing wont raise the current enough to burn all the others. maybe if 1/3 failed at the same time.... but one only? it wont change much the grid V=IR.

 

[Kornphlake]

It's pretty common to run LEDs in series and parallel with groups of LEDs serviced by a single resistor, for example you have a 6 volt battery and 3 volt LEDs and you want a total of 9 LEDs powered by the battery, so you use 3 groups of 3 LEDs and 3 resistors and each LED is underpowered slightly.

I just saw a flexible strip LED array in a trade magazine a few days ago, if I think about it I'll look for it tomorrow at work and post a link, it might work out for what you need. The way it was built all you'd have to do is supply DC power, depending on the voltage requirement of the strip you might be able to use something like a button cell watch battery.

 

[Dirty]

I just saw a flexible strip LED array in a trade magazine a few days ago, if I think about it I'll look for it tomorrow at work and post a link, it might work out for what you need. The way it was built all you'd have to do is supply DC power, depending on the voltage requirement of the strip you might be able to use something like a button cell watch battery.

that would make it a lot easier....would be sweet if you could find it!

 

[Kornphlake]

Here's the link:

http://solutions.3m.com/FFCe

It looks like they are not available to the public yet but there might be something else similar out there, try searching google for "LED array."