LED lights

As a rule of thumb, each LED will take 20mA of current. You can actually drive them higher (25mA or even 50mA if you pulse them like I do when I do any LED sign circuit designs) but use 20mA as a safe working limit for use on a continuous DC supply. To work out the series resistance you need to get the current limit to 20mA, just use Ohm's Law: R = E/I where I = 0,02 for 20mA. You get the answer in Ohms. For example, if you have a 12 Volt supply, then R = 12/0,02 = 600 so a 600 Ohm series resistor is necessary. Just use the next standard value up, for example a 620 or 680 Ohm is common. Mind you, I'm ignoring the voltage drop across the LED and just using the value of the supply voltage. In reality E would be a little less (say 1,7 V or so). When using more than one LED, you can either run them in parallel or series. The voltage drop across an LED is around 1,7V, ~ 1,9V so if you need to run several LEDs in series, you can quickly get to the point where your 12V supply won't be enough to kick the string over. I prefer to have them all wired in parallel. The disadvantage to this is that you need a separate series resistance for each LED, but on the other hand if one dies, the rest of the cluster will still operate and so if reliability is important, you'll still have light. If you want any more elaboration, feel free to email me.

Rohan,
Check out this link http://www.geocities.com/george_tlc/led.html
good info on LED conversions.
Mark

BTW I think you are on the right track with LED's.
I fly for Qantas- we have just taken delivery of three new 747 ER's in the last month or so ( we are THE launch customer) and nearly all the cockpit lights are LED on the new planes!
Not much to do with camping I know, but you get the idea... well sort of?

Rohan
Plexus' suggestions are Ok except he overlooked the power loss in the series resistors. Putting many LEDs in series such that the total forward voltage drop matches input voltage (say about 6-8 with a smaller series resistor to take care of voltage fluctuation) will provide much more light (the number of LEDs in series times) for the same 20ma current draw ... a much more efficient array!