Help with LEDS

[Xandas]

I'm a Noob when it comes to LEDS. Now If you have a resistors in the leds path of electricity will it stop all but what is needed? I have a 450W Power supply, and I want to add 3.5 V -5mm-8000MCD Blue led. Now first options for ways to connect 10+ Leds to a power supply without damage? Thanks for any information.

On http://www.v3leds.com/product_info.php/cPath/23/products_id/43


Resistance(Ohms) = (Supply Voltage - Forward V of LED)/ Current (A)


5mm
3.5 volts
8000MCD
20mA

+ 1 FREE Resistor* per LED you purchase!

Available Options:
Resistor: 470ohm

wouldn't you need a 75ohms or close to it.. They offer you a free 470ohm. Wouldn't that be to much?

 

[SarverSystems]

Simple.

You need 2 LEDs, right?

Grab 2 of em, and hook em end to end.

+5VDC ------- +LED- --------- +LED- ------ GROUND

Do that 5 times, and no resistor needed!

Yes, you can hook hundreds if not thousands of them to even a 100Watt PSU.

Don't believe me?

See any resistors? Nope. There aren't any. There's 68 LEDs in that group right there, all running off one molex connector.

 

[SarverSystems]

You wanna hook em up like this, but with only 2 per set, not 4 like I have.

 

[Xandas]

Now when I install to the Computer How would you recommend? A while back I put one in and it fried becauise I took a a Fan and cuts its wires (kept the wire with Power adapter), and sodered it on... What would you recommend for computer installation >

 

[SarverSystems]

That IS for a computer installation.

 

[Xandas]

This sound right (correct)?


LED--> Connector---> Powersupply

Now when I install the Connector and the wires there are four holes.

This correct?


- +
|_|_ _
o o o o<(last one is yellow on standard>
---------.

 

[HHunt]

Regarding voltages and molex:

Red is +5V, yellow is +12V, black is ground (0V).
This used to be explained on PSUs (together with all the other colors). One thing I'd like to see return

 

[Xandas]

Ok thank you for your help. Also Last question you say grab 2 leds. If I did one 3.5V LED on 5V Line.. What would be the result (i.e. The led is grounded too). Thanks for pictures and information though. I want to pimp out my computer before college.

 

[jpnelson83]

Short answer, you'll fry your LED unless you have an inline resistor. If you take two LED's that have a forward voltage of 3.5v you have a combined forward voltage of 6v. Now LED's have a range of voltages that they can operate at. There is usually a min voltage and a max voltage and then there is the normal operating voltage. So by undervolting each LED by .5v your not going to do any damage.

 

[lukeh182]

sorta OT but not necessarily..... if you want a good deal on blue LEDs go to eBay. there is a guy on there from hong kong that sells 50 blue LEDs with 50 resistors for $9.99 if you use buy it now feature. they are very good LEDs too. i actually got 51 LEDs and 51 resistors. <----sad that i actually counted huh!?!?