No difference in brightness on original 16x16 display
Mike,
I decided to take my original 16x16 LED matrix (with 2n3906 transistor/resistor) and ULN2803's and replace one row of the transistor / resistor circuit with the new Fairchild P-FET. I had used a 22 ohm resistor from the LED anode row to the Drain. The source went directly to the 5v 20 A power supply (I also tried the whole circuit - logic chips and all). The Gate went to the SX52 bottom row lead (to have it driven by the SX52). The display came on fine with it going into it's normal scrolling. However, the P-FET row had no difference in brightness (fairly dim like the rest - unless it's really dark).
This make's me think that the issue was not that they needed more current as originally it drew less than 100 mA anyway. I believe that the LEDs are just not that bright.
When using the new 8x8 LED matrix modules on the MAX7219 - these are lit up much better than the handsoldered individual 256 LEDs in the first LED matrix.
I suppose the next test should be to simply wire up (4) 8x8 LED modules in the same fashion as the original 256 handwired LEDs as in matrix 1. If they are brighter than the handwired original ones, then the issue will have been with using older (possibly very low MCD) rating.
I will work on this over the weekend and let you know.
PS: The new 5v 20A power supply provides a nice 5.05v out so it appears to be regulated well.
More later...
Mike,
I decided to take my original 16x16 LED matrix (with 2n3906 transistor/resistor) and ULN2803's and replace one row of the transistor / resistor circuit with the new Fairchild P-FET. I had used a 22 ohm resistor from the LED anode row to the Drain. The source went directly to the 5v 20 A power supply (I also tried the whole circuit - logic chips and all). The Gate went to the SX52 bottom row lead (to have it driven by the SX52). The display came on fine with it going into it's normal scrolling. However, the P-FET row had no difference in brightness (fairly dim like the rest - unless it's really dark).
This make's me think that the issue was not that they needed more current as originally it drew less than 100 mA anyway. I believe that the LEDs are just not that bright.
When using the new 8x8 LED matrix modules on the MAX7219 - these are lit up much better than the handsoldered individual 256 LEDs in the first LED matrix.
I suppose the next test should be to simply wire up (4) 8x8 LED modules in the same fashion as the original 256 handwired LEDs as in matrix 1. If they are brighter than the handwired original ones, then the issue will have been with using older (possibly very low MCD) rating.
I will work on this over the weekend and let you know.
PS: The new 5v 20A power supply provides a nice 5.05v out so it appears to be regulated well.
More later...