# LEDs Wiring

Discussion in 'The Projects Forum' started by jeremyhaberman, Aug 7, 2013.

1. ### jeremyhaberman Thread Starter New Member

Aug 7, 2013
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0
Hello everyone,
I am build an overhead panel for my home cockpit and I need some help. I will have some DPST switches that will have one set of poles going to a usb interface board my my flight simulator to recognize the command (this part I understand). I want to wire a LED to the second set of poles. My confusion is that I want to have multiple LEDS all controlled separately (by their own on/off switch) but powered by one power supply, is it possible and how can I do it. I really need the help.

Much Thanks,
Jeremy Haberman

Last edited: Aug 7, 2013
2. ### mcgyvr AAC Fanatic!

Oct 15, 2009
5,082
1,104
yes its simple.
wire each led with its own current limiting resistor and done.

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3. ### tubeguy Well-Known Member

Nov 3, 2012
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If you need help on calculating current limiting resistors, please post your LED specs and LED power supply voltage.

Last edited: Aug 7, 2013
4. ### jeremyhaberman Thread Starter New Member

Aug 7, 2013
3
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I want to use 5 red LEDs at 2.2 v and 20mA, 5 Blue LEDs at 3.2v at 20mA, and 3 green LEDs at 3.2v at 20mA. I want to use a 5vdc 300mA power supply. Each LED will have is own toggle switch. What type of resistors do i need.

5. ### mcgyvr AAC Fanatic!

Oct 15, 2009
5,082
1,104
Resistor values are calculated as follows.

R= (Vin-Vf)/A
Where
Vin is power supply voltage
Vf = LED forward voltage drop
A=led current in amps

Then you need to calculate the wattage for the resistor where
P=2 x (I^2 x R)
Where P watts
I = led current in amps
R=resistance

Example (for red LED)
Resistance
5-2.2 = 2.8
2.8/.020 = 140 ohm resistor or slightly larger

Wattage
.02^2 = .0004
.0004 x 140 = .056
.056 x 2 = .112Watts (1/8W resistor)
The times 2 is a "safety factor" to keep the resistor from running too hot.

In general LED's do fine anywhere from 10ma to 20ma (more current the brighter they are)
BUT once you start going over 20mA the lifespan is usually decreased.. So always shoot for no more than 20ma

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6. ### jeremyhaberman Thread Starter New Member

Aug 7, 2013
3
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Thanks, I like how instead of just telling me straight up which one to use yoU tell me how to calculate using the formula because I need to learn this stuff.

Oct 15, 2009
5,082
1,104
No problem..