Connecting Multiple led's to Arduino.. Max Led's without Frying chip.

i wanted to connect the multiple led's to the arduino on each pin.
if i connect 10 led's to pins 3 to 13 on the Arduino with resistor 300 ohms, does it damage the chip?

The pins are rated to a max of 40mA so you can do so safely.

Weedpharma

weedpharma:
The pins are rated to a max of 40mA so you can do so safely.

Weedpharma

true, but keep in mind that 40mA per pin is an absolute max, and that there are other current limitations related to ports - For axample, you can't safely drive simultaneously 8 Leds at 30mA connecting them at D0-D7 pins , because you'd ask 240mA on a port which can source max 150mA .

Have a look here

The small SMD LED’s on the Arduino boards are modern Hi-sensitive LED’s, which only requires some 2-3mA to light up very bright.
This is done with a 1K (1000) ohms resistor.

If you are using same kind of LED’s, you will not need a 330 ohm resistor, which will provide around some 8mA through the LED.

Mind you he said 10 LEDs, and 330 ohms gives 8 to 10 mA each, total if all lit no more than 100 mA so it should be fine (if the LEDs are the only thing drawing any significant current). :grin:

Mind you that LED's are non-linear components, not obeying Ohms law.
Then it is really impossible to predict what will happen, if you try calculate a resistor.

It may blow up, because of un-predicted behaviour, as we are dealing with an undefinded component here.

Until we solve that, I believe everyone should keep hands off LED's and resistors, as they wont know what they are doing, by definition. :smiling_imp:

I and several other people have attached several LEDs to the Arduino without damaging anything. I think you'll be alright :slight_smile:

Squirt_5432:
I and several other people have attached several LEDs to the Arduino without damaging anything. I think you'll be alright :slight_smile:

Lucky fellas -
Ya dont even know the theory behind them working LEDs ::slight_smile:

Table 30.1 on page 313 of the [u]Atmel Datasheet[/u] says 40mA absolute maximum per pin, or 200mA absolute maximum total.

[u]Ohm's Law[/u] says Current = Voltage/Resistance.

Don't forget the voltage drop across the LED (check the LED's data sheet if you want to be 100% sure). With ~2V across the LED there is 3V across the resistor. With 3V across 300 Ohms, that's 10mA per LED. 10 LEDs @ 10mA would be well within spec.

You are assuming that LED's comply with Ohms law.
They dont, as they are non-linear components.

If you mix linear and non-linear components and apply Ohms law, you will get an un-predictable result, as the theory behind is not documented.

You are on dangerous grounds.
How will you know that he LED is not radiating Gamma rays then ?
Or even death rays ?

Ah well, life is dangerous ... :smiling_imp:

Not a funny joke.

Ohm's law always works and LED's can't emit death rays, even if you drop them into the sun.

MorganS:
Not a funny joke.

Ohm's law always works and LED's can't emit death rays, even if you drop them into the sun.

How con you be so sure ?

The atmega chip is also a nonlinear component, which does not comply to ohm's law.

Ohms law discussion - be warned !