External Power Supply Info

**wjohn** · 08-11-2007, 10:59 PM

Originally Posted by RJ

I would say you will be fine. When I first built the board I pushed it much harder than I let you guys to see when it would start killing Leds. Then I turned the current down for the best compromise I could get between not killing leds and brightness. Before we turned the current down the panel had a peak of 4 amps for a couple of microseconds just as the switching happend. You power supply would not mind this as the output caps will absorb it. After the peak it would fall to around 1.5 amps. After that we dropped the current so its well within you p/s capability. So have fun!

Also, RJ's first design did not include the Current Limiting Resistor on the MBIs. I added this feature to the PCB to ensure that the Display LEDs were not being over driven.

I am pleased to see that the actual measured loads are <1 amp. <4 amp would be worst case without the current limiting resistors.

That being the case, a 15 watt PSU would be good for 1 to 2 panels.

John

RJ · 08-12-2007, 06:03 PM

Actual I did but they got missed on the first proto board you did. I missed them because the first testing I had done was full current to see if the leds would survive. I solder them to the bottom and still have that board. I asked you to add the resistor spots after that. you changed the resistance I suggested afterwards from my suggestion and so my personal controllers run a little less current than what the rest of you are, but if the leds don't die to fast its not a problem. In fact if you look at the how to on computer christmas and look at my board that pre dated the much nicer ones you laid out you can see the resistor is there.