I am learning to wire and interface my 8x8 RG leds dot matrix common cathode. for the moment the first steps run perfect.
However i have some doubts about its use taking into account the ideas that i want to develop with it.
My first doubt is if resistances with different values should be used for red and green leds. I used 1K resistances for all the leds, but i observed that green is less intense, and for that reason, when i turn on at the same time red and green led for the same dot, the orange is not so different than red. So, the solution is to use different resistance values, or to use different values at the digital pins to control the intensity of each color or their mixture?
My second doubt is related to how i want to use the dot matrix, but i don´t now if it is possible. I would like to use it such as a group of bargraph. I mean, i would like to show by lights the relative values of different sensors (temperature, humidity, etc...). In that way each 2 columns (or rows) are assigned to one sensor. When the value is low, only one, two or three leds of 2 rows are on in green color. When the value is medium, moreover the three green leds, other one, two or three leds are showed in orange. And when the value is high, moreover the 3 green leds and the 3 orange led, other one or two are shown in red. And the same for other two rows related to a different sensor. However, i don´t know if this is possible. By the way, in order to save pins in the arduino 2009, i would like to use 2 74HC595 shift registers to control all the leds. However, is it still possible by the use of this IC's?? I saw that it is necessary to send the information to the 74HC595 with a binarry sequence such as B11000000. But in that way i can only control two columns each time... waht made so complex to figure it out all the possible combinations of values coming from the sensors (medium-low-hih-low, or medium-high-medium-medium,... and so on). Just only to know if it is possible in order to think about other solutions (to use 4 bargraph, of course).
Thanks!!