So, I recently acquired this RGB Led matrix but ,because I'm new to electronics, don't know some stuff that i should.
I'm planning on driving this board using 4 74HC595 Shift registers and my Arduino uno (later on I' ll try to switch it to an arduino nano)
My questions are:
What resistor value do you guys suggest that i use to drive each set of colors?
If the RGB LED matrix has different values for Red than for blue, should i use a different resistor value?
I was planning on using a 5v power supply (the Arduino's) but i can use a 9v, which one should i use?
I have attached the datasheet of the matrix (here is the link too). If more information is needed please let me know, Thanks!
If you use only 595 registers to drive the matrix you will have to use very high value series resistors to avoid overloading the pins connected to the anodes. This will mean that the matrix well be very dim and perhaps only visible in a dark room.
Each pin on the 595 can source a maximum of 35mA to one of the matrix anodes. This would them have to be shared between 8 red, 8 green and 8 blue leds, 24 in total, so about 1.5mA each. With a 1 in 8 multiplex, the leds would receive about 0.2mA on average which is about 1%of the leds maximum current.
So I would say that your other questions are not relevant until you have decided on a better circuit to drive the matrix.
Another consideration is colours and how many you want to see. If you just want red, blue, green, yellow, cyan magenta and white, then that is easy with shift registers, but of you want to mix more colours, then you may want to consider chips with pwm outputs. You can mix more colours with shift registers by using the Arduino to perform the pwm in your sketch, but this may be crude and limited by the speed of the Arduino.
We can suggest many ways around these problems using different chips or transistors but our answers will depend on how bright you need the matrix to be and how many colors you want to mix, and how complex or simple you want to make your project.
Thank you for your reply and sorry about my absence (I 've been out for some time). To continue with the matter i have used 150 ohm resistors for the red and 250 ohm for the other colors. Regarding the dimness, when i powered it on, i believe they were bright enough so I'm guessing it isn't an issue (doesn't need to be too bright because it is an indoors project). Also, i did notice the lack of color mixing but at the moment i can only count with the 595s so i am sticking with those colors, although for future projects i would like to keep it it simple and maybe switch it up a bit. May you please let me know of any chip or transistor circuit that can make it easier to build or program? Also do you happen to know any examples that i can use to learn more about multiplexing (if it is a rgb led matrix like mine would be best) cause I am having some troubles regarding the programming.