the old thread is kinda bugged (the site dont loads and is white :/ ) so i deleted it.
i am planning a 7x20 rgb led matrix.
i want to get the leds off a rgb led stripe like this: http://www.ebay.de/itm/LED-Strip-SMD-Streifen-Band-RGB-300-5M-Leiste-5050-12V-LD62-/250970230849
because i have much time but limited cash
. these leds have 3 anodes and 3 kathodes, but i would combine the anodes to a common anode to ease the wire-ing.
thinking that i would have to handle a lot of leds (140
) i read through a few topics and decided i would multiplex the leds 1:7 to keep the leds bright.
the leds im propably going to use need (according to a datasheed i found) between 2.5 and 3.5 V depending on the color channel. they are usually supplied with 20mA per color, but can handle up to 80mA pulsecurrent.
--> 20 leds * 3 colors * 80 mA pulsecurrent = 4,8 A !
i thought of using some transistors or mosfets to supply the current, but i am not sure how to do it exactly.
should i multiplex 1:20 to keep the current low? but will the leds be bright enough and be flicker free?
how would i control the matrix best?
i came up with 8x 74HC595 shift registers to conroll the R, G and B cathodes of the leds and one binary to decimal converter to control the anodes.
these ic's would be controled by an arduino uno with the help of the ShiftPWM library (http://www.elcojacobs.com/shiftpwm/
), which can controll the shift registers.
sorry if i express things a little bit complicated
do you have any suggestions about powering the leds or any general improvements?
i want to try to spend little cash as possible
thanks for your help