i just need to dim 3 colors which is easy with arduino BUT i want to connect at least 10 LED's per digital out, probably taking 200mA. that makes a total of 600mA.
i read somewhere the board can only supply 300mA. is there any solution other than a complex LED driver with lots of channels ? as i said, i just need 3 PWM signals. simple LED driver hint would be cool !
and another stupid question, what happens if the current is higher than the board can supply ? can the board go up in smoke hence be destroyed ?
thanx, angel
oh dear, writing a post and then finding a possible solution in the forum http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1177356283
could this be it ?
I'd go with this sort of a scheme, from the playground... Arduino Playground - HomePage
You could reduce the component count if you had a higher voltage power supply available by putting several LEDs in series with a single resistor, but you would have to calculate the value for your resistor.
When you overload the +5v supply on an Arduino the voltage regulator will overheat and shut down until it cools enough to come back on.
If you are running off an external power supply you can use the raw power voltage to drive the LEDs and not worry about overloading the +5v regulator. Say you have a 9v power supply, figure it probably makes about 10v just to be safe. I don't know what the forward voltage drop over your LED is, you'll have to either look that up or measure it, but lets guess 1.8v. When the transistor is turned on it will have a voltage drop of about 0.2 volts. Let's put 3 LEDs in series for a 5.4v drop over the LEDs. That gives us 10v - 5.4v - 0.2v = 4.4v... we need to drop 4.4v over the resistor. Maybe you have nice 20mA capable LEDs... V=IR... 4.4v=0.020a*R.. R = 220 ohms, we even hit a standard resistor value. How fortuitous. The clever ones are now saying "Look! I could put 5 LEDs in series, use a smaller resistor, be more efficient and have a smaller component count.", which is true, but the current would also be much more sensitive to changes in the supply voltage and since it is an unregulated wall wart I don't trust it.
