so to give a little bit of background, I want to experiment with led matrixes. I have multiple Arduino Nano boards, and have done small projects (9 LED bank with simple animations).
So I know that each pin can only supply a limited amount of current (perhaps 40mA).
So my test circuit of a 2*2 matrix has P1, P2 for positive rows, and N1 and N2 for negative columns. All LEDs in row 1 have anodes wired together to P1, all cathodes in column 1 are wired together. also resistors are hard wired to each LED.
Now I there's plenty of current with a small matrix but if I get 9*9 LEDs I would definitely run out of current both onboard and per pin/row.
I successfully used this schematic to wire in a 2n7000 mosfet (200mA max) to P1. http://www.learningaboutelectronics.com/images/N-channel-MOSFET-switch-circuit.png
My own circuit looks somewhat like this rather hard to understand ascii diagram
P1--*---*-- ....l...l.. P2--*---*-- ....l...l.. ....N1..N2
The dashes are anode wiring, the l's are cathode wiring and the N/P 1/2 are the header wires. (I plan to expand this to 4*4*4 so I want to be able to turn them all on without worrying about current limitations)
To clarify I set P1 HIGH, and N1 LOW to get the top-left led lit. I want 1 transistor per P (for positive, anode) wire, and one per N (negative, cathode)
So here's my question. Do I have to buy a P-channel mosfet in order to accomplish this? Or is there some way to do it with the 2n7000. (I bought 100pcs on eBay)
If I must buy P-channel transistors, can you provide a simple schematic and the equivalent to the 2n7000?
Thanks for reading and hopefully answering my post!