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troypiggo
16-03-2009, 06:15 PM
I'm thinking about building a box for my gear, and want to put a light in the lid of it to make it easier to find things in the dark. I was thinking that it'd be good to have some sort of variable power so can do a dim light and more powerful if needed. Maybe have 8 LEDs, and the switch can either turn on 4 or 8 or something like that.

Now I am a total electronics noobie. I have no idea what sort of LEDs to get, how many will be enough. Could anyone point me in the right direction of a website for a howto, and/or give me a shopping list of what I'll need. Because I'm such a noobie, you'll need to take it back to basics - LEDs, resistors, what do I mount them on, what type of soldering iron do I need, what's a solder sucker and do I need one? Thanks for your patience.

peter_4059
16-03-2009, 07:38 PM
What sort of power are you planning to use Troy? This will influence what you need. If you have use 12V you can buy LED's with built in resistors from Jaycar. You can put a dimmer on these and they might work with 9V but easy enough to try.

troypiggo
16-03-2009, 07:53 PM
Good question. Was originally thinking 12V off the car battery, but that means more leads etc. Maybe some rechargeable batteries would be the go.

Glenhuon
16-03-2009, 08:25 PM
Hi Troy.
Only thing that varies with the circuit for LED lights is the resistor size. Depends which voltage you feed em. LED's typically draw around 20 milliamps of current (0.020 amps).
If using 2 rechargable AA batteries, series resistor would be 120 ohms (R = V/I, R = 2.4/.020 = 120).
For 12 volt, 600 ohms (12/.020 = 600).
Some of the white ultra brights draw a bit more, up to 40 milliamps, but a standard red one will be about 20.
You can chain up to 4 without drawing too much juice from the battery on 12v and probably 2 on the AA's. A 60 ohm resistor on the AA's and a 240 ohm on the 12v. 1/2 Watt resistors would do the job in both cases.

The draw from a 12v battery would be pretty small, only about 80 - 100 ma, for a 4 led chain.

Cheers
Bill

troypiggo
16-03-2009, 08:34 PM
Thanks mate. So any links/tips on how to actually build it? What/how to mount it etc? Soldering, switches etc?

kinetic
16-03-2009, 08:44 PM
Troy, Bill, Peter,

great suggestions so far....

idea for something that could easily do the job.
Maybe a temporary measure to get you up and running:

For the equivalent of about \$20 of parts, you could buy a 4 pack
of the cheapest solar garden lights in a pack of 4....put them all
in the garden during the day and use one in your light box at night :)

I cannibalised the bits from a whole set of these.

They have all the parts you need:

2 x (sometimes just 1) rechargeable NiCad
1 x ultra high brightness LED (put some red cellophane over it)
1 x switch to turn it off
1 x solar cell to recharge it for free during the day :)

Steve

RobF
16-03-2009, 09:33 PM
The guys at Jaycar Woollongabba were happy to spend 10-15 mins sketching circuit diagrams and finding bits and pieces for me when I was building my lightbox Troy. You could do a lot worse then asking them for help.

troypiggo
16-03-2009, 11:57 PM
Thanks again guys. I'll have a chat with the Jaycar dudes.

Astrolabe
17-03-2009, 09:53 AM
Hello Troy

As a non technical solution to your problem, you may consider a standard issue two red LED astronomical deemable torch from one of the astroshops. A nine volt battery will last you for about a year depending of how often you use ot. Just secure it to the box by velcro. I believe that they quite cheap.

Just a thought

Regards

George (astrolabe)

Roger Davis
17-03-2009, 12:55 PM
I bought a rear window mounted brake light from the auto shop with 8 red LED's in it. I hooked up a 9v battery and it's been running for the last 4 years. Because the LED's are mounted at about 70° I set it pointing into the box and it illuminates it more than adequately. A reed switch in the box turns it on and off as I open and close it. Simple, cost me \$12 for the light, \$1.50 for the reed switch and scrap speaker wire and a 9v battery.