# Thread: LED's for creating Angel Eyes!

1. ## LED's for creating Angel Eyes!

So, I was thinking about creating some nice Angel Eyes for my car and have read some nice guides, seems simple enough! The problem is that my math skill isn't the best these day!

I was thinking of putting 2 led's as this:

to light up the acrylic rod, their stats is:
Voltage (max) 3,4 V
Voltage (typisk) 2,8 V
Current 20 mA
More Specifications
If I remember the lessons from school the way I was thinking of connecting them thats called a parallel connection but all the guides I read is just how to calculate them in series.

So, anyone good with LED's, How much resistance do I need there!

2. Originally Posted by Naesstrom
So, I was thinking about creating some nice Angel Eyes for my car and have read some nice guides, seems simple enough! The problem is that my math skill isn't the best these day!

I was thinking of putting 2 led's as this:

to light up the acrylic rod, their stats is:
Voltage (max) 3,4 V
Voltage (typisk) 2,8 V
Current 20 mA
More Specifications
If I remember the lessons from school the way I was thinking of connecting them thats called a parallel connection but all the guides I read is just how to calculate them in series.

So, anyone good with LED's, How much resistance do I need there!

Many LED's in the market today operate on 12VDC, so there's no need to configure resistors in order to use them. Are there any special characteristics with the one you chose that have convinced you for this particular application?

Nevertheless, here's an LED Calculator with other great solutions: http://www.superbrightleds.com/led_prods.htm

3. ehh, you still want current limiting resistors, though, even if they run directly on 12V.

See http://led.linear1.org/led.wiz for a good calculator.

For example with the above LEDs :
Source Voltage : 12V
Diode Forward Voltage : 3V
Diode Forward Current (mA) : 20
number of LEDs in array : 2

you can pick how it draws the circuit for you, I like schematic

gives one 1/4W 330ohm resistor, connected after the two LEDs (all connected in series)

4. Originally Posted by biosehnsucht
ehh, you still want current limiting resistors, though, even if they run directly on 12V.

See http://led.linear1.org/led.wiz for a good calculator.

For example with the above LEDs :
Source Voltage : 12V
Diode Forward Voltage : 3V
Diode Forward Current (mA) : 20
number of LEDs in array : 2

you can pick how it draws the circuit for you, I like schematic

gives one 1/4W 330ohm resistor, connected after the two LEDs (all connected in series)
Thanks for the great help, I was looking at that site earlier but I was worried that since in the schematic they seem not to be paralell, apparently there's no difference then!

and btw, shouldn't the resistor be before the LED's, and not after since it's supposed to limit the current going into them? as you can see I get confused by to much technical stuff...

Might aswell ask the follow up question too, the LED's are supposed to light up 2 acrylic rings like the picture below, the info about the one's Im looking at says they are 8000mcd in strength. would that work or is it even too much?

5. I would recommend parallel for a more consistent brightness (it will cost you one more resistor).

Series is only good for a few resistors and reduced wiring. The LED's have to be the same spec for them to be a uniform brightness. Parallel is good in case you want to have 2 different colors and mix them. Two LED's in series of a different color wont work to well.

It doesn't matter if the resistor is before or after the LED, the resistor limits the current in the entire circuit, not just before and not after.. if that makes sense

The higher the mcd (brightness) the better as you can always reduce it later.

-dave

6. Originally Posted by Civic Modz
I would recommend parallel for a more consistent brightness (it will cost you one more resistor).

Series is only good for a few resistors and reduced wiring. The LED's have to be the same spec for them to be a uniform brightness. Parallel is good in case you want to have 2 different colors and mix them. Two LED's in series of a different color wont work to well.

It doesn't matter if the resistor is before or after the LED, the resistor limits the current in the entire circuit, not just before and not after.. if that makes sense

The higher the mcd (brightness) the better as you can always reduce it later.

-dave
yeah, thats why I was planing on using parallel connection, like in the picture I posted in the first post. that should work as parallel right, since a seriall would be +LED-+LED- while I was hoping to connect each of the two LED's + to the same wire and thus using 1 resistor to each set!

And yes, a small glimmer of memory came back with the closed circuit... all those hours in the lab at school so many years back

7. Yep, your pic is parallel though it looks like both leads are connected together. Parallel is like this:

Just use that LED calculator site to get the value of the resistors. Just enter the values for 1 led and use the resistor value calculated for both LED's.

-dave

8. Originally Posted by Civic Modz
Yep, your pic is parallel though it looks like both leads are connected together. Parallel is like this:

Just use that LED calculator site to get the value of the resistors. Just enter the values for 1 led and use the resistor value calculated for both LED's.

-dave
Ahh, now I see the problem... yes, both are connected together, I was hoping that would work so I wouldn't need to use 2 resistors for the setup...
I'll just extend the wiring a bit and it will probably be ok and then shrinkwrap them somewhere out of the way

9. Originally Posted by Civic Modz
Yep, your pic is parallel though it looks like both leads are connected together. Parallel is like this:

Just use that LED calculator site to get the value of the resistors. Just enter the values for 1 led and use the resistor value calculated for both LED's.

-dave
hmm 1 resistor should work just have to use the right one, it would have to be either 2x or 1/2 of the other 2 resistors i forget which, but it should be the same thing, its just that instead of having our circuit take 1x of Y and X values your circuit will now just require 2x of Y and X well not the voltage but the current

i could be wrong, this might work with a regular light but maybe not a diode, since that is different a bit

10. This is a better calc...
http://led.linear1.org/led.wiz
You'll need a pair of 1/2 watt resistors if you wire them in parallel, or 1/4 watt if you do it in series...(with 12V regulator)

They aren't going to be very bright, as they are only 20mA LED's. A pair of 70mA would be better, but you'd want to run them in series, as you'd need (huge!) 2 watt resistors to properly limit them in parallel...
Also, are you going to use a voltage regulator, or wire it straight into the car?
I'd recommend regulators, with capacitor protection, unless you want to be replacing LED's all the time...

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