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| Thread ID: 52676 | 2004-12-26 08:58:00 | How to make a USB Light | Willuknight (6541) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 307643 | 2004-12-28 09:38:00 | Also you can buy cheaper red LEDs from DSE. They're actually brighter then what i used, and only about $2 each ! but you will need a different type of resistor. 8,000mcd Ultra Bright Red LED $5 www.dse.co.nz 3,600mcd Super Bright Red LED $2 www.dse.co.nz i been thinking of doing this for a while too... tho mines alot simpler... I blew a LED when connecting it to the 5v's on the usb tho...*scratches head* You probably didn't have the right resistor. You need a resistor to limit the foltage going into the LED. Just ask at where you bought the LED, or at DSE what type of Resistor you need to limit the 5volt down to the led's level. |
Willuknight (6541) | ||
| 307644 | 2004-12-28 09:47:00 | Hardly seems worth the hassle when you can but one which looks a lot smarter and costs less www.dansdata.com www.dansdata.com Greg, those links are american, so they're like NZ$20. You can actually buy these things in NZ from pc shops, and trademe. Its about $9-$15 for the lower budget ones. Add in about $2.50 or $5 for postage, and my one is actually cheaper. And if you use a cheaper LED its definately worth your time :D |
Willuknight (6541) | ||
| 307645 | 2005-03-30 03:54:00 | sorry to dig up old threads but i have a question for ya Willuknight i want to use maybe 4 LED's to get the effect i want and was wondering, as i have forgotten 5th for physics if i will still need a resistor all will this use all 5 volts if i run them in paralle ??? chur cuz :thumbs: |
dumbskate (6669) | ||
| 307646 | 2005-03-30 04:14:00 | You must limit the LED current to below its maximum level. Typically 20 mA is used. So each LED should have an appropriate resistor in series to limit the current. As LED's are not always all identical, paralleling them with one lower value resistor is not always succesful. Resistor value (for DSE Z4031) is (Vusb - Vf LED) / 0.02 amps = 5v-2.6v /0.02 = 120 ohms Wattage is .02 x .02 x 120 = .048, so a standard miniature 0.125 or 0.25 watt 120 ohm resistor in each LED positive lead should be fine. Total current = 4 x .02 = 0.08 amps (80 mA) and a standard USB port will deliver 500 mA. Should be OK. |
godfather (25) | ||
| 307647 | 2005-03-30 04:55:00 | The important thing to remember is that the forward voltage of the LED depends on the wavelength (colour) . (I think Vf=1234/wavelength in nm) . DSE catalogues have a page giving the voltages . "White" LEDs are an exception because "white" doesn't have a wavelength . They are actually a blue LED, with a fair amount of UV, and there are phosphors included in the plastic encapsulation to produce the white light . They are "fluorescents" ;) Vf is 3 . 6 -4 . 2 depending on manufacturer . For useful light, the 1W ones are quite impressive (and 3W and 5W even more so) . Unfortunately they are still very expensive . You could run the 1W ones off USB . . . 350mA current (at a bit over 3V for white) . They need heatsinking, and current regulation . You can buy the USB plugs from Jaycar . +5 is pin 1, gnd is pin 4 . But for a small torch I use the small ones with a number of high intensity white LEDs using 3 AAA cells . Much easier to carry than a computer . :) |
Graham L (2) | ||
| 307648 | 2005-03-30 05:36:00 | I agree Graham. I have several of the small 6 LED - 3 AAA cell ones around here. At $12 each they could not be built for the price. | godfather (25) | ||
| 307649 | 2005-03-30 05:47:00 | I've even considered these torches as a source of cheap high intensity LEDs. But my only use for high intensity LEDs is in a torch ... :) | Graham L (2) | ||
| 307650 | 2005-03-30 10:05:00 | thanx guyf for th useful info and all the calculations the reason i am doing this is not for a light source but to dress up a cooling plate i am making for my laptop when it is at home. i wanted to place the LED's behind grooved perspec's sheeting to get the illumination effect. so thanx again and im off |
dumbskate (6669) | ||
| 307651 | 2005-03-30 10:40:00 | If you want a cheaper place to get the LED's from, leds.co.nz is a great place to find them - way cheaper than DSE at something like $2 per 15000mcd LED! :) | wintertide (1306) | ||
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