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Cobra power consumption


#1

How much current should a basic cobra +4.3" screen pull?

Mine hover’s around 400mA is this normal?

This is using a regulated external 5v supply…

Cheers Ian


#2

Yes that is normal. The LCD back light is the reason.

FEZ Cobra itself cosume 180mA to 220mA
http://www.tinyclr.com/compare/


#3

I don’t mind that sort of consumption but Chris and Brett both say they can run the cobra+ LCD with USB, only they are supposed to be good for 500mA, but my 5v from the USB is dropping past 4.6v…

I think my USB port is very weak

Cheers Ian


#4

The USB spec says that the port can be as low as 4.5V I think so that is within the specifications.


#5

I got curious my usb ports on the asus are pushing 5.6 volts at 800ma. On my touchbook 4.7 volts 400ma. Holy divergence batman but i would guess thats all in spec.


#6

I suppose you are measuring the voltage at FEZ Cobra 5V.
It is dropping because there is a protection Schottky diode in serial with the the power source. the forward voltage for this diode is about 360mV