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Author Topic: Pin Out Current Draw.  (Read 456 times)
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Edison Member
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Am i Right?... each pin can supply up to 40ma of current.

I have a couple of transistors on the out of the pins to drive some high powered products... (LED's, Relays, etc)

question is... let's suppose an LED of 800ma draws current because something failed, the LED becomes dimly lit,
i presumed the LED would simply give brightness of 40ma's worth of brightness, and it does, and it's not died
on me (yet) through accidentally maxing out a single pinout.

So is it safe to deliver max current on any given digitalpin?
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No...

Quote
*NOTICE: Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
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nr Bundaberg, Australia
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So is it safe to deliver max current on any given digitalpin?
Not for long, 20mA is normally considered the safe limit.

______
Rob
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Rob Gray aka the GRAYnomad www.robgray.com

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i presumed the LED would simply give brightness of 40ma's worth of brightness,

No, there is not internal current limiting or control action inside a output pin to keep current at less then 40 ma. If you try and draw more then the 40ma max rating then more current will try and flow and thus risk destroying the output pin. Safe output current must be limited or controlled via the external circuit wired to a output pin, usually via a series resistor of proper value.

Lefty
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There is also a maximum total limit of 200mA for all pins combined.
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Check out my experiments http://blog.blinkenlight.net

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There is also a maximum total limit of 200mA for all pins combined.

As well as a maximum limit for each 8 bit port.
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