Hey fellas,
I am confused with the current coming out of power pin 5v. It is giving me 10mA current. However official says that it should be giving 40mA and 3.3v pin should be giving 20mA. But I aint getting these values when I checked with multimeter,
Any help please?
Thanks
Wait-the 5V pin is giving you only 10mA?
What's drawing the current?
OP might have measured the current of a pin with a DMM set to current, effectively shorting the pin to ground.
That could have destroyed the pin.
A DMM set to current, using the 20A socket, might be 0.2ohm. Most of that will be the resistance of the test leads.
Leo..
Good point. Say goodbye to the pin!
Wawa:
OP might have measured the current of a pin with a DMM set to current, effectively shorting the pin to ground.
That could have destroyed the pin.
A DMM set to current, using the 20A socket, might be 0.2ohm.
Yep that's what I was thinking, although I didn't explicitly realise a DMM set to current is basically a short. Might be interesting to test that with another meter... I'll do that when I get home.
Resistance depends on the current setting/socket.
Sometimes fuses are in series. A DMM from a "student" has usually blown current fuses.
The inbuild 20A current sense "resistor" is basically a piece of thick wire.
The meter leads could be 0.1-0.2ohm each, depending on the qualtity.
You can see that resistance when you put your DMM on low ohms.
Reading will never be exactly zero.
Leo..
He was referring to the "power pin" and "3.3V pin".
What do you suppose?
Duhhh. Was blinded by the 40mA value.
So he must have shorted the supply rail.
That should be ok, because the 5volt regulator would have gone in protection mode.
Leo..
I duno guys, Im new in this arduino stuff. I put one wire in 5V pin and connected to resisotor and LED (in series)
and other leg of LED and ground was connected to DMM in series. And When I checked current it was only 10mA. what is efficient to check current?Thanks
Well depending on the forward voltage of the LED (say about 2 or so), and the value of the resistor to drop the balance (5 - say 2 = 3 say) then maybe the 10mA is what you would expect.
Using those figures, and using Ohms Law (arranged to say R = V/I) did you have a resistor of about 3/0.01 = 300 Ohms?
300 ohms is exactly right for 5V, 2 volt drop from LED, and 10 mA.
Isaac96:
300 ohms is exactly right for 5V, 2 volt drop from LED, and 10 mA.
Why else did you think I posted that?
Duh. :-[