The leds will be 5v leds, do I even need transistors?
Hi, I'd like to build a little circuit board with about 5 or 6 leds on it. Each led would be driven from it's own pin on the arduino. I'd like to supply the power to light the leds from an external power supply so I'm guessing I'll need to use transistors to switch the power.
Seeing as I have 5 or 6 leds, I thought rather than using 5 or 6 separate transistors on my little board it would be nice if I could find a single chip which contains the transistors.
Please could someone tell me if such a chip exists and if so what is it called ? If I can find out what I need to buy I can ebay it.
The leds will be 5v leds
With the TLC5940, what is the voltage drop of the device when it is "on" ?
Suppose firstly, that i want to connect a 2V, 20 mA red LED and drive it with 5 voltage directly.I can then determine that I want a resistor which will drop 3V at 20 mA, therefore 150 ohm.Suppose now, I want to turn the LED on and off using the TLC5940 between the LED and ground.I still need a resistor, apparently, because otherwise the chip would generate too much heat.