LED questions

[ivwshane]

I have a bunch of LED's that I got from an old iphone display and I'm planning on using them to make a marquee light but I have a couple of questions on a couple of things.

First, the LED's seem to have a narrow beam of light, is there a way to widen the beam?

Second, I have two strands of LED's, roughly 16-18 LED's per strand all ran in parallel how do I connect these to a computer power supply?

Currently I can run both strands of LED's off of 3 D cell batteries with no problems.

Would it be just a matter of hooking it up to the red and black wires on a molex connector?

[arzoo]

If you file the tops of the LEDs flat, you may get better diffusion. It might help if you posted some pics.

[fatfingers]

You will likely need a resistor or the LEDs will fry from the 5v.

[Twinpanther]

Depending on the color of the LED's (Red, Orange, Yellow, Green run about 2.1v while True Green, Blue, White and UV run about 3.4v) you most likely would need a resistor on the negative LED post.  They'll light up without it but most like will burn out much sooner than you'd like.  No expert here by any means but just info I picked up DiYing my own for my reef aquariums.  

[fatfingers]

Depending on the color of the LED's (Red, Orange, Yellow, Green run about 2.1v while True Green, Blue, White and UV run about 3.4v) you most likely would need a resistor on the negative LED post.  They'll light up without it but most like will burn out much sooner than you'd like.  No expert here by any means but just info I picked up DiYing my own for my reef aquariums.  

Sounds right.

[richms]

Much sooner meaning straight away IME

Also, since the blue and green appear brighter then the red, calculate the resistor for the red and use that on the other 2, he blue and green will be a bit dimmer but nothing major.

[ivwshane]

Sorry for replying so late. Here is a pic of the LED (sorry for the low quality).




Would I need a resistor for every LED or just for each string? If i do get a resistor how do I wire it to my pc's power supply?

[ivwshane]

Can anyone answer the above question (how many resisters do I need)?

What type of resister do I need (yes I'm a noob when it comes to this stuff).

[fjl]

Back when I used to work with LED's I believe I used to put 1k Ohm resistors for each LED.

[Franco B]

You need to know a few details before you can figure out what resistors to use and how to wire them.

• Source voltage you are using (either 5v or 12v from your PSU)
• LED forward voltage (should be somewhere around 3v)
• LED forward current (should be somewhere around 30mA)
• The amount of LEDs you wish to light

When you know all of them put them into [this] calculator and it will tell you which resistors you will need and how to wire them (series/parallel/combination).

[ivwshane]

You need to know a few details before you can figure out what resistors to use and how to wire them.

• Source voltage you are using (either 5v or 12v from your PSU)
• LED forward voltage (should be somewhere around 3v)
• LED forward current (should be somewhere around 30mA)
• The amount of LEDs you wish to light

When you know all of them put them into [this] calculator and it will tell you which resistors you will need and how to wire them (series/parallel/combination).

Thanks.

Since these are second hand led's am I screwed if I don't know the values (other than the source voltage)?