LED Voltage

[reddog418]

Just making sure I won't blow out my LEDs, I used this site (http://www.casemodgod.com/led_calculator.htm) to figure resistors. I went to the series calculator and I figured I could run 6 LED's on a series without a resistor, at least that's what the calculator said. My LED specs have this: (Foward Voltage: 2) - (LED Current: 20mA)

Is that right?

Another question: when using a parallel circuit, do I put the resistor on before it hits any LEDs, so the resistor would be the first thing the electrons hit?

Last minor question: what's the difference between +12v and -12v?

[Malatory]

Just making sure I won't blow out my LEDs, I used this site (http://www.casemodgod.com/led_calculator.htm) to figure resistors. I went to the series calculator and I figured I could run 6 LED's on a series without a resistor, at least that's what the calculator said. My LED specs have this: (Foward Voltage: 2) - (LED Current: 20mA)

Is that right?

Another question: when using a parallel circuit, do I put the resistor on before it hits any LEDs, so the resistor would be the first thing the electrons hit?

Last minor question: what's the difference between +12v and -12v?

1st one of the best sites I seen on LED is done by a modder. http://led.linear1.org/ he also has a wizard on his site that gives you a good diagram on how to wire. This is a good reason to use it :).

since your using the 12 Volt Rail. Yes 6 would be the max you can do. Quick simple math.

You have 12 LED and each are 2 Volt with a 20ma rating. Your source of power is 12 Volts.

Since 1 LED is taking 2 Volts of power with would leave you another 10 Volts to use. You can add anther 5 LED for a total of 6 and leaving 0 Volts. Any more you will be lowering the amount of power that is going to the LED and in turn Diming it / or not lighting it up.

Question 2: The resistor can be placed anyware as long is you have it. Tipically it is placed either at the front or the End.

+12 is Positive power (which is needed to power LED)
-12 is Negitive Power (Best way to discribe this is the power is flowing from the grown to the starting point - Water fall that flows up the Hill).

[Frakk]

reddog look for some basic electronics tutorials. i assume you already know what volts, amps and ohms mean. when you have leds and resistors in series, the volts add up (thatswhy you can have 6 leds on 12V). volts dont add up if its in parallel and you need to reduce the voltage to every one of them, or you can reduce it before they go parallel. ohm's law is also good to know when you need to figure out how much resistance you need. anyways just google for electronics tutorial and selfeducate for 10 mins.

[reddog418]

Ahh, sweet, I found this. This is what I was looking for: http://led.linear1.org/led.wiz

Thanks guys.

[Guttenaffe]

GAH!!
NOOOOOOOOOOOOOOOOOOOOOOO

NEVER RUN LEDs WITHOUT A RESISTOR!!

LEDs are CURRENT driven devices, they only need voltage to break the barrier between the N and P junction. Though alot of these LED calculators are correct (not all but a large majority of them) is because they are copies of one another but the people who wirte them have no understanding about LEDs. It happons that the LED page linked here is one of the better one I have seen. The thing is thought if you have five 20mA max 1200mcd 2V forward bias voltage LEDs that run off and a 10V source you technically can not hook them up and get your 20mA current and the max mcd brightness.

I have an article coming along about this I've been so busy with my 6 week (compressed from 15 weeks) Statics & Dynamics class I've had little time to work on it of late. It is over in a bit and I'll be able to finish it.