Hey guys this is my first post here but I hope to be on here more often. I have been modding for a little while but I am always limited by my limited knowledge of electronics. Anyway the current mod that I am working on is nearly done so I decided not to make a full thread on the whole mod (maybe for the next one). So I have this jumbo 10mm. LED that i bought from radio shack and I want to use it for the power on light for my computer case. What I need to know is how I can power this thing to give me the brightest light possible and still have it as the power on light (in place of the one that plugs on to my mobo). Here are the specs of the LED that were on the box it came in: 10mm round 300mcd brightness Absolute Max Values Forward (supply) voltage 2.8V Reverse Voltage 5V Forward Current Peak 100mA Continuous 60mA Power Dissipation 168mA and you probably dont need to know this stuff but here it is anyway... Opto-Electrical Characteristics Forward Voltage (typ) 2.0V Forward Current 40mA Luminous Intensity (typ) 300mcd Peak emission wavelength 635nm If this has already been asked then point me to the right spot please. If not I would really enjoy some help. I suppose that it could be run off of the power from one of the molex connector but after that I have no clue about if 12V or 5V is about right or what other electronics would be needed in between. Thanks guys and girls and sorry this is so long.
I'm not sure what current LED's connected to the power header run at, so if you wanted "maximum brightness" you could run this LED from a molex connector. This would still enable it to function as a power LED. You'll need to use a (5 - 2.8)/0.06 = 37 => 39 ohm resistor. Connect up the LED as shown in my quick guide at the bottom of the Electronics Sticky: http://forums.bit-tech.net/showthread.php?t=61317&page=1
Not a lot. My last 2 boards had 330R led resistors, current board 220R. So with 5V and probably a 0.2V saturated VCE loss, that's around 8.5-13mA for a 2V Power led. The HDD Activity led is even less as there's also a 0.6V diode loss to take off.
Thankyou, you guys have been very helpful. I have one last question. I see in your calculation for the number of ohm resistor I would need you used 60mA. Is there a reason you didnt use the "Peak" 100mA value? Or maybe something in between 100 and 60? Would that damage the LED? Thankyou again. Ill post some pictures of the case when I am done.
100mA is the peak current. This is the maximum current the LED can withstand for a short period of time. If you try to run the LED at this current continuously you'll almost certainly lead the LED to destruction. You may get away with running the LED at 70 or 80mA, but the increase in brightness will be minimal, if at all.
