Arduino output low is at 0.5V

Hello,

I am using the mega 2560 to drive two opto isolators.
My problem is that when the output is low is stays at around 0.55V.
This is enough to let some current flow, and activate the opto slightly.
Anyone have any ideas?

Regards
Bob.

Which part # opto?
How is it wired?
Do you have pinMode (pinX, OUTPUT); in your code?
Do you have the grounds connected?

did you use series resistors ?

-Malhar

Yes according to the specifications you can have a LOW of this voltage. How much current is it sinking. Bit it is probably one of the things wrong above, it generally is with new comers.

BobEdge:
Hello,

I am using the mega 2560 to drive two opto isolators.
My problem is that when the output is low is stays at around 0.55V.
This is enough to let some current flow, and activate the opto slightly.
Anyone have any ideas?

Regards
Bob.

0.55V won't activate any opto isolator even the tiniest bit if that's the voltage across
the LED. Its physically impossible.

Sounds like perhaps you have the optoisolators between 5V and the output pin? That
means you have 4.45V across the optoisolators?

Or perhaps you have it wired in a non-standard way? You have series resistors?

Thank you all for the suggestions.
It turned out to be a leaky transistor in one of my opto isolators.

Regards
Bob