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LED wiz - which LED's?
tony.silveira:
hey guys,
i have a 32 port LED wiz lying around and have an idea for my CP. basically, i want to drive 32 standard red LED's (not RGB). Red LED's on GGG's site say:
"Includes appropriate resistor for 5v connection"
if i read that correctly, that resistor is needed when driving the Wiz with a 5v connection from my power supply. So here are a few questions i have if anyone can answer:
Will the LED's need this resistor if the Wiz is being powered only thru USB?
Can the Wiz even drive 32 LED's solely with USB?
i'm looking at flush mounting the LED's with the top of my panel and am looking at these flat top LED's:
http://www.allelectronics.com/make-a-store/item/LED-167/4MM_Red_Flat-Top_LED/1.html
so, not sure if i have to have that resistor on these or not
any help is appreciated!
BobA:
Whether it is USB 5V or your molex connector you will still need a resistor to run it so it does not burn up.
32 LEDs require approx 20 ma x 32 = 640 ma or .64 amp. This is over the max draw for a USB outlet so you should wire with the molex providing external power.
If the LEDs do not mention 5 or 12 V then they are probably provided bare without the resistor.
Mysterioii:
Yeah that's just a plain ol' LED, you'll need to provide current limiting resistors for each one.
tony.silveira:
thanks guys! if i did my math correctly per the LED wiz instructions, here is what i just bought:
LED, FLAT TOP, 3MM, RED; Bulb Size:T-1 (3mm); Forward Current If:20mA; Forward Voltage:2.25V
RESISTOR, METAL FILM, 140OHM, 400mW, 1%; Resistance:140ohm; Resistance Tolerance:± 1%; Power Rating:400mW; Voltage Rating:250V
PL1:
--- Quote from: tony.silveira on May 08, 2012, 08:52:37 pm ---Red LED's on GGG's site say:
"Includes appropriate resistor for 5v connection"
if i read that correctly, that resistor is needed when driving the Wiz with a 5v connection from my power supply.
...
i'm looking at flush mounting the LED's with the top of my panel and am looking at these flat top LED's:
http://www.allelectronics.com/make-a-store/item/LED-167/4MM_Red_Flat-Top_LED/1.html
--- End quote ---
Tony,
Electronics is like plumbing: Voltage=water pressure, current=how much water flows through
Most LEDs are designed to work with up to 3.2 or 3.3V. If the voltage is too high, it will be like connecting a garden hose to a fire truck--It won't be long before it bursts. Use the resistor with ANY 5V connection.
As for the Flat LEDs: No manufacturer + no manufacturer P/N + no specs = avoid like the plague unless you get help from someone with a good background in electronics. :)
If your heart is set on those flat LEDs, I recommend using the LED calculator to design your circuit. http://ledcalc.com/#calc
If you want to check/test the circuit before building it into your CP, you can use a solderless breadboard to test brightness, current flow, etc. Amazon has one for under 6 bucks.
http://www.amazon.com/Solderless-BreadBoard-tie-points-power-rails/dp/B005GYAIES/ref=sr_1_4?s=electronics&ie=UTF8&qid=1336530277&sr=1-4
You'll need some test leads and jumper wires to go with it. I use the USB power tap cable from GGG to power my board, but you can tap into the power+ground from your computer power supply if you like.
Under the plastic exterior, the breadboard has connections like the attached picture of a solderable breadboard.
Scott
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