How to connect 15 LEDs in parallel ?

[wilson82]

LEDs

May i enquiry if i need to connect up 15 leds which 10 is 5mm, 5 is 3mm ones. I need to connect them using parallel method to form certain shape. Can i do that or i have to use a different method.

 

[WA]

Re: LEDs

You need to look at data sheets for LED's

There shouldn't be a problem mixing LED's. BUT.

Different LED's have different current draw requirements.
Look at the data sheets to determine max foward and reverse current.

From there you can determine what current sinking resistors you'll need.

Hope this helps to a successful design
wa

 

[cesardelahoz]

Re: LEDs

You can do it, but depending of the use of your circuit, and the leds characteristics, you'll probably want to adjust the leds bright, because of the diference in the impedances, and you'll have to add some resistors to your circuit.

 

[hill]

LEDs

No. If you connect it in parallel, you're running into the risk that some LED with higher forward voltage are not light up.

 

[LAKMON]

Re: LEDs

What is your LED's colour. If them colour are same. you can connect them. Because same colour as same voltage.

 

[Big Boy]

Re: LEDs

Basically, you can connect leds in parallel, but you need to add a resistor in serie with each of those leds. Don't connect LEDs directly in parallel, each single LED need a resistor. Else, some LEDs won't light-up.

So, tie each leds, individually, with a resistor, and then, connect this in parallel.

To know the resistor value, you need to know the voltage drop of the leds (forward voltage) and the current rating of those leds. Then, if:

Vcc - is your main supply voltage
Vf - is your LED forward voltage drop
If - is the LED forward current rating

Then, the resistor value you need is

(Vcc-Vf)/If

For example, many leds have a 1.7V forward fortage drop, with a rating of 10mA (many of the regular 5mm leds).

Then,
Res = (Vcc-Vf)/If
Res = (5V-1.7V)/10mA
Res = 3.3V / 0.010A
Res = 330 ohm

And you calculate this for every diodes.

 

[wilson82]

LEDs

Lakmon=> im using green leds for a set and red for the other set of design. so same color connect up of a same circuit.
anyway thanks guys for ur replies. =)

 

[platonas]

Re: LEDs

Put all Green LEDs in series and calculate their series resistor for the proper current limit (about 10-20 mA). Do the same for all Red LEDs.
If you are going to supply both Red and Green from same voltage, then the series resistors should be calculated at this voltage, acconrding to the Vf of each color and the current passing through.
Example: 10 Red LEDs with Vf=2V and required current of 15 mA give a total of 10*2V=20V (we need a supply of more then 20V.
Suppose a 24V supply.
The voltage drop on the series resistor shoul be 24-20=4V
For 15 mA to pass throough you need R=V/I hence
R=4/0.015=266.6 Ohms
The nearest standard value is 270 Ohms.
Regards
Platonas