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 Post subject: ideas for laptop lighting
PostPosted: Mon Oct 05, 2009 6:04 pm 
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So I have a Toshiba Satellite A215-S4817, nothing to look at really. But I got thinking, if I put blue LED's in the speakers and maybe some on the front of it, that would look pretty darn cool. So of course now I have to give it a shot. My main problem is powering them. How would I do this, I'm not too experienced with pulling power from a laptop, and I'm not sure what kind of voltage LED's use.


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PostPosted: Tue Oct 06, 2009 4:49 am 
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LED voltages vary slightly depending on type, power output and color.. usually about 1.5 - 5v or so.. you can use any pretty much voltage LED as you will use a current limiting resister to match it to your power source.

you want all the wiring internal right? best bet for power is probably tap the +5v line to the HD or optical.

give me a bit and Ill get some specifics on blue LEDs and what resister to use for +5v.


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PostPosted: Tue Oct 06, 2009 5:43 am 
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OK here are a couple examples. used radio shack.

LEDs are diodes (duh) and as such they need a current limiting resister in series with them to limit what they can draw as they will present themselves as a short circuit when forward biased. the resister will also drop the voltage.

keep this formula in mind:

Resistance (in ohms)= Voltage (in volts) divided by Current (in amps)

rectangular

3.2v, 20ma

so for 5v supply to get 20 ma

r = 5 / 0.02
resister= 250 ohms

or this high output

5v, 30 ma

resister might be too much of a voltage drop with 5v supply so tap into 12v (if the notebook has that voltage? hmm this one may not be suitable but Ill include it anyway)

r = 12 / 0.03
resister= 400 ohms

dont worry if you cant find an exact match to the resister, use the closest one higher in value. each LED should have its own limiting resister.


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PostPosted: Tue Oct 06, 2009 12:44 pm 
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Thanks for all the advice. With that 5V LED, can't I just tap the HDD's 5V power circuit, with no need for resistors?


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PostPosted: Tue Oct 06, 2009 1:23 pm 
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no, the LED will draw too much current and burn out. they will draw as much current as you let them. hence the current limiting resister.

you would need a 167 ohm resister to limit it to 30 ma, but that will also drop the voltage below 5v, so the LED may not fire up or will be dim.


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