I don't know much about power but thought I could use a 4xD battery pack for an Uno + (official) WiFi shield. It seems to power the Uno but the shield doesn't turn on. Is there an obvious reason for this?
Side note: the shield seems to stay powered on if I first power with USB and then unplug the USB, leaving the battery pack plugged in.
Wifi shield schematic;-
Vcc connect with Vin. to make your system work, you need one more D battery, now you have 7.5 v and connect it to Vin. This will meet Uno's requirement.
Depends if alkaline or NiMH, alkaline are 1.5V per cell, NiMH are 1.3V per cell.
MarkT:
Depends if alkaline or NiMH, alkaline are 1.5V per cell, NiMH are 1.3V per cell.
True, I am overlooked.
for NiMH we need 6 D.
Just as side info, the Rayovac C and D NiMH cells are both rated at 3000 mAh. So if smaller size is important, the C cells might be the preferred choice unless the cells being used actually have differing power capacities.