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[Solved] max. current LED-Pin on Witty Pi3 mini?

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(@maexx)
Posts: 2
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Hi,

I'm using Witty Pi3 mini and want to add an external Button with integrated LED-Ring.

Does anyone know whats the maximum allowed current to draw on LED-Pin?

 

The manuel says nothing abou that and I dont want to fry this output if its coming (for example) directly from the microcontroller.

 

Thank you guys for your help and greethings from Ausria!

Markus

 
Posted : 03/02/2024 3:37 pm
(@admin)
Posts: 203
Member Admin
 

On Witty Pi 3 (Mini), the pin with "LED" label in that unpopulated header is directly connected to pin 5 of ATtiny841. The white LED on board connects to it via a 10K resistor.

According to ATtiny841's datasheet (in the "Absolute Maximum Ratings" section), one IO can provide up to 40mA current. This is way more than enough to drive an LED (usually a few mA will be very, very bright already). You will need to put a resistor between the LED (in the button) and that pin, to avoid possible damage (on LED or/and on ATtiny841).

 

 

 
Posted : 03/02/2024 3:57 pm
(@maexx)
Posts: 2
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Topic starter
 

That was fast! Perfect Support, thank you so much! 

Back to hobbydesk at this sunny weekend 😆 

 
Posted : 03/02/2024 4:08 pm
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