LED Moving Display design engineering and math
T&E Engineer
Posts: 1,396
I beleive I have my general design rules in place for LED moving display projects (using 8x8 bicolored matrix modules) as attached for both 5v and also using an 8.8v 5.68A PS2 power supply. However, I found out recently that the LED modules I have been using are 20 mA and not the 5-10 mA originally assumed. Can someone verify that my calculations are correct for this type of a design?
The calculations are based off of 5mA but if recalculated for 20mA, this means I would need a much higher current rated p/s. What is confusing to me is that I have already built a 8x40x2* display and it works ok for display. I have not used the powerfull 6 A P-FETs (although I will soon) but simply 500mA ULN2982 Anode drivers for the rows. Without using the P-FETs I read less than 300 mA which is a far cry from 6 - 13 A that I would expect. Perhaps this is because the ULN2982 and UDN2803s are only allowing 500mA max.
Ideas and comments are welcome.
Here is a link to what I am refering to:
http://forums.parallax.com/showthread.php?p=670333
* 8x40x2 refers to 8 row segments by 40 column segments by 2 colors (red and green).
The calculations are based off of 5mA but if recalculated for 20mA, this means I would need a much higher current rated p/s. What is confusing to me is that I have already built a 8x40x2* display and it works ok for display. I have not used the powerfull 6 A P-FETs (although I will soon) but simply 500mA ULN2982 Anode drivers for the rows. Without using the P-FETs I read less than 300 mA which is a far cry from 6 - 13 A that I would expect. Perhaps this is because the ULN2982 and UDN2803s are only allowing 500mA max.
Ideas and comments are welcome.
Here is a link to what I am refering to:
http://forums.parallax.com/showthread.php?p=670333
* 8x40x2 refers to 8 row segments by 40 column segments by 2 colors (red and green).
