I have an led and a picaxe 40x, can i put 3v into the anode and then attatch the cathode to an output pin and when i make the output low will it make the led come on? just dont wanna burn out my kit.
Yes you can but you need a current limiting resistor. The normal rule for a pic pin is that it can supply a maximum of 20mA and so you would need a series resistor of at least 200Ω. I normally use 330Ω.