Yes you are right, 256 x0.060 is indeed 15.36A, so 15.4A then. Blimey, I didn't realise that the project would take over 15amps to run!!!
I have also just tried the 5v 6 amp power supply and at first the display didn't light up, so I re inserted the barrel connector and the display is now working. **!! Again the voltage on the display is the same 3.5 volts.
Well as I said, the project is running fine now with a 5v 6amp power supply.I put a red wire from my meter onto a vcc pin soldered onto a pcb board, then the gnd wire to any gnd points on the breadboard or gnd pin or gnd of the display, the reading was the same, nominally 3.5v.I have attached a picture of the wiring I followed for the said project. Maybe that will tell you more than I can.Thanks
How many panels are we talking? Just 1 strip of 4 8x8 blocks? Those have a duty cycle of 1/8. You have 32 on at a time at most.With a generous 30 mA per LED, you get close to 1A not accounting for dead time. I have one of those. I just tried and measured. With all LEDs on at highest brightness, it pulls just under 650mA. You can power it from a phone charger or a laptop USB port.