LED strip creation

[maxxis]

Hi guys. I need a little help with the right resistors etc to fabricate a panel containing about 10 LEDs.

The strip is to be used in a car for audio install enhancement and will run of the the 12V supply in the car

Any recommendations? I havn't worked with electronics in about 12 years but I can still solder

[Samaya]

You will need a 220Ohm 1/2Watt resistor per LED, placing all the led's in parallel. I worked it out for a 3.3V drop and 40mA current supply per LED.

[maxxis]

So I will get the following then

10 x 220 Ohm 1/2Watt resistor
10 x Hyper Bright LEDs

Thanks man. That really helps a lot. Thank goodness I remember my electronics a little to know what parallel is

[WiK1d]

This is a pretty handy link

[-Prometheus-]

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[maxxis]

What would you suggest then?

[maxxis]

Thanks for the link Wik. Looks like a 220 Ohm is correct according to the calculator.

[Prime]

if you are still in doubt, you can always ask the electronics supply place where you buy your LED's.

[Samaya]

2200 doesn't sound right, and neither does 220. 1/2 watt is just unnecessarily large. Since you are using nonstandard LEDs you will have to look up the forward voltage drop and the optimal current.

What doesn't sound right? Rled = (Vcc - Vled drop)/Iled? Or what about P = V*I? If these do not sound right then you will have to talk to a gentleman going by the surname of Ohm...

@ Maxxis: Just ask the guys you are buying the LED's from what the voltage drop is for the LED's. You can then substitute the Vdrop of the led into the formula above and calculate the resistor value. If you need more help just PM me

[maxxis]

Will do thanks man

[UrBaN]

With Regards to this

I used the link Wik posted above, but I have a few questions...

The LEDs I want to use in an LED strip have the following specs:

Specifications:-
Intensity: 160 - 250mcd
Wavelength: 405 - 410nm
Forward voltage at IF = 20mA: 3.3V
Power dissipation: 100mW
Viewing angle: 30°
Forward Voltage: 3.0 V (10mA) - 3.6 V (35mA)

I'm a little confused by the two bold statements.

Why are there differing forward voltage and current ratings? This obviously determines which resistors I should use, so I'm now not sure what to buy.

Suggestions please guys?

[WiK1d]

Use this: 3.6 V (35mA)

[Samaya]

The more current you are drawing for this LED you are using, the brighter it will be. If you use a white LED and draw too much current it will start to give off a blueish tint. At this point you HAVE to switch off unless you want to reduce the life of the LED by significant amounts...

[UrBaN]

They are UV LEDs. Samay, can you please check the link I posted above and check if my design is correct? My electronics know-how is dangerous

[Samaya]

The safest way to power the LED's in your strip is to put a resistor in series with each of the LED's. Like so:


You'll notice I used 100 Ohm resistors for those LED's which is just for indication. You should use 56 Ohm or 47 Ohm resistors for your LED's. The ideal resisitor would be 40 Ohm and you would be able to use a 39 Ohm resistor but 47 Ohm is going to keep your LED's working for longer.

[UrBaN]

Thank you very much

[Samaya]

No Problem. Glad I could help

[UrBaN]

Here's a quick question.

Would normal copper wire (twinflex for example), work well as the conductor, or should I use something else? The distance is not long (maybe 40cm in total) so the resistance etc should be negligible, correct?

[Samaya]

Yes that will be correct. Just remember you need 5Vdc for this circuit.

[UrBaN]

Which I can take from a Stiffy drive connector on a standard PSU, yes?

[Samaya]

Yes and its usually the red wire.