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Laptop cases. Custom ;)

Spec-Kie

Spec-Kie

Well-Known Member
Hey there loverly people of the android comunity ;). I have a dell inspiron 1545 with a half decent cpu and about 4 gig of ram. And it runs pretty well. I plan to mod thr case :) cutting the case puttin mesh on for better air circulation .. also i plan to add some leds to the casing. Like the ports and the lid. Only thing is i have no idea where to wire them 2 i no that LeDs are polarity consisous so i could wire them in series from a usb port? As most leds are between 3.3v and 5v i cant see this been a problem as usb are powered by 5v? How does this sound??
 
1) The airflow design of most laptops is optimized for cooling. It forces air to flow from the coolest parts to the hottest parts, then out. Cutting the case to change that could cause the laptop to overheat. (Even removing it from the case, then running some CPU-intensive operation for a couple of hours, could destroy it.) It's not just how much air it gets, it's the path the air flows in that's important. Opening the case limits you to convection and radiation cooling. Heat radiates way from hot components (possibly overheating nearby components) and flows upwards. But a CPU needs air FORCED to flow past it - the more air that's moving, the more cooling you get. 95C air sitting all over the top of a 96C CPU isn't going to cool it much, and that's what happens when a fan isn't forcing the air to flow away from the CPU. The channels and fins in the case direct the airflow from the fan for best cooling. There are copper heat pipes in there too, but some of the cooling depends on the case design. (Which is why some cheap Dell desktops lose video cards so often - poor thermodynamic design.)

2) To power an LED from a 5 volt source (like the power supply of a laptop [you don't have to pick the power off at a USB port], put a 330 ohm resistor in series with either lead of the LED and you'll get a pretty good light. Higher resistance will lower both the current drawn and the amount of light. At about 1,000 ohms the light will be about as dim as you'd want it to get.

DON'T try to power an LED from the data leads of a USB port (there are 4 pins, 2 for data, 2 for power) - they aren't made for that. If you want to see blinkenlights you'll need an op amp (and a few resistors) to pick up the signal and drive the LED. (And you'll probably want a bicolor LED, so you can see it flashing between red and green as the data lines go high and low.) But just putting an LED and resistor across the data lines will render that port useless until you remove the LED.
 
Yeh i know about the date lines and stuff lol. The casing was just a little thought to think of to mod as in replace the plastic mesh with some metal mesh i didnt want to totally rearrange the the air flow. My main casing mod was going to be adding 2 plexi glass windows either side of the touch pad but thay can come a different time :) .. its mainly the LEds i wanted to come to grips with lol. So rukbat what would you reccomend take the power from?? I only want a glow from the leds as i am using a difuser anyhow ..
 
As Rukbat said, you could tap straight off the power supply. If you have a DMM, you could take measurements from the power supply section and find either a 3.3v or 5v source and tie in there.
 
Yeah that seems like a better plan then doesnt it .. would i run them parralel or series? The power suply u mean is that the power jack??
 
The power jack feeds into the power supply.

Typically, your brick will generate a DC voltage in the 12-20 volt range, and the power supply will take that and create several different voltages for use throughout the device: 3.3v, 5v, 12v, etc.

You will probably want to parallel the LEDs, but don't go nuts-- every LED you add is a current drain on the power supply, and so your mod is going to kill your battery much faster.
 
I get you see the power jack is on a board separate to the main mother board! So will i just tap into the pins ? Or would it be better to pull from the battery ??
 
Neither. Find the main power bus on the motherboard (there will be two lines, going around most of the motherboard, that are thicker than most. Using a voltmeter (it doesn't have to be a digital voltmeter - any meter that can show you 0,1 Volt iincrements will do), you should find 5 Volts between the 2 lines. That's where you get your LED voltage. Use any ppoint on each line that already has something soldered there.

Put an LED and a resistor in series. Put them on the 2 solder points you determined above. (Check the web to determine the proper polarity. The resistor can go on either lead, but the longer lead, with or without a resistor on it, should go to the positive side (+5 Volts) and the shorter site, with or without a resistor on it, should go to the ground (or -5 Volts) side.

Do the same thing for all the other LED/resistor pairs. The LEDs are in parallel. (You may want to solder a thick (about $14) solid wire a couple of inches ling, to each solder point, then solder your LEDs to those wires, so you don't have 10 LED wires soldered to the sme spot on the motherboard. (Doing tht neatly takes practice.) Make sure you at least tape all exposed wires. (I use heat shrink tubing of just about the right diameter on work like that - I don't shrink it, just use tubing that's just the first size larger than too tight to slide onto the wire. The heat of soldering the end of the wire will shrink the end of the tube and hold it in place. [Put the tuning on the wire before you solder it.] That's for the LEDs and resistors. If you use wire to connect them all to, leave it bare until you're all done, then tape each wire.)

You're probably going to have to use some hookup wire to go from the LED/resistor combination to the motherboard - the LED and resistor leads are pretty short.
 
Right i have all of my components sorted ready to only thing i need is my resistors and to make i have every thing sorted. The power will come from the main power bus ;) i think i need to get some pictures up and make it more visable :) see i plan to use about 15 3.3v 1.8mm leds :) .. .. obs they need to be in all different locations :) .. so the wires are all going to be different lengths does this make a difference? When i have worked out the resistance i got a number of 110? On the equation of R=V/C when i done a internet calc to make sure. It came back with 68? The specs of the leds are 3.3v with a FC of 30MA is this correct?
 
So each LED will use 99Mw Therefore 10 LEDs should draw just under 1A You need to be sure that the 5V lines can take the extra load without anything else suffering under-volts.
 
And the resistor should be 56 ohms. Starting with 5 Volts. 3.3 Volts appears across the LED, so 1.7 Volts has to appear across the resistor. 1.7 Volts divided by 0.03 Amps is just over 56 Ohms. A 68 Ohm resistor (one for each LED) will give you just a slight drop in brightness, cooler operation, longer LED life and less battery drain. (You have to use available values - in 10% values, it goes from 56 to 68 with nothing in between.)

Each LED/resistor pair will draw about 28 mA, so your total current draw will be about .42A (Each pair will be dissipating about 0.14 Watts.)

The effective resistance of each LED is about 110 Ohms, so each LED/resistor pair in series is 178 Ohms. 5 Volts across 178 Ohms is: W = E^2/R and I = E/R, so 0.14W and 0.028A. 15 of them will draw 15 times 0.028 or a little under half an amp. Get as close to the 5 volt output of the power supply as possible, or you'll lower the 5 Volt line to the point that you may have problems.

@DavidL:
99mW * 10 is 990mW, or just under 1 Watt, not 1 Amp. 990mW at 5 volts is 0.198A.
 
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