Forgive me. I don't understand this stuff very well. I am designing a RGB lighting system for my living room (to go above the crown moulding), I've done up a quick diagram of what I think will work (or hope will). sorry I didn't know the symbol for transistor
The LEDs are common anode 10volt 1amp, so they will be run in parallel by a 10volt 7amp constant current source. I plan to use an Arduino to create the pwm signal to control a number of transistors, mosfets, igbts, bjt, or something else... I had originally settled on 3 transistors per led (one for each cathode), but after thinking about it more, if the transistor like device acts as a fast switch than I should be able to run the whole color strong off of one device for a total of 3.. correct me if I am wrong. Also, I didn't draw them in, but I believe I need a resistor on the anode of each led, and because the red runs at a lower voltage (2.5v vs. 3.2 for blue and green) I will need some sort of control on the red's cathodes (I was thinking just another resistor, but something I read somewhere made me think it was more complicated talked about a resistor and a capacitor in series). So, assuming i can get the arduino to output pwm the way i need, will this work?
It's not difficult to google the word transistor and see what the symbol is. You need a base resistor in the transistor. I can't see where the constant current supply is. So your circuit might make sens but as you don't use the right symbols i can't tell what you are doing so I don't know if it will work.
I updated the circuit pic with the correct pic for the transistor. I didn't realize it would matter, but if it does, it is fixed now. I actually didn't have google (or any internet) when I was drawing. I also put in resistors, though I didn't value them. I believe the resistors on the blue and green cathodes will be the same, but the resistor on the red cathode will need to be different as the red led runs at 2.5V rather than the 3.2V of the other two... I was also mistaken in my thinking in my original post... I was using wrong numbers from when I was trying to run these in series which obviously didn't work. they are 3.2V 1 amp LEDs. I will run 7 of them with a constant current source (at 7amps).
Will this setup work? assuming I choose the right resistors...
is there a better way?
is there a limit on the number of transistors I can run (in parallel I assume) from one controller pin?