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Adafruit METRO 328 - Run 3-4 5mm Leds w/resistor on one pin?
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Adafruit METRO 328 - Run 3-4 5mm Leds w/resistor on one pin?

by mdeisenzimmer on Wed May 29, 2019 10:51 am

I am building a certain movie prop. (something related to time travel) I currently have arduino uno r3 running this and it works, over night even. 4 pins blinking in sequence with 3 5mm Leds attached to EACH PIN with one 220ohm resistor! Works. I notice the Arduio uno specs state only 20mA per pin. Again it ran overnight just fine.

My question is since the forward current of the 5mm leds is 20mA each and I am running 3 in parallel(60mA) would the (Adafruit METRO 328 - ID: 2488) handle this better since it's specs are higher for the current draw needed?

Here is a video of it working
https://photos.app.goo.gl/1SuuTHCnXjrnCBFg8

Capture1.JPG
Capture1.JPG (136.44 KiB) Viewed 75 times

mdeisenzimmer
 
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Re: Adafruit METRO 328 - Run 3-4 5mm Leds w/resistor on one

by adafruit_support_bill on Wed May 29, 2019 1:18 pm

The Arduino UNO and Metro 328 are both based on the same Atmega328P processor. So the pin specs are the same.

It is also very likely that the pin output voltage is sagging due to the overload, so your LEDs are seeing less than 20mA each.

The 20mA per pin is more of a rule-of-thumb than a hard spec. The complete spec is not so simple since it depends on other factors such as loading on other pins of the same port and loading of the processor as a whole.

See Section 28 - starting on page 258 of the datasheet - especially all the footnotes.

http://ww1.microchip.com/downloads/en/D ... asheet.pdf

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Re: Adafruit METRO 328 - Run 3-4 5mm Leds w/resistor on one

by mdeisenzimmer on Thu May 30, 2019 8:31 am

Thanks for the update, kinda figured that would be the answer.

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Posts: 11
Joined: Sat May 09, 2015 11:35 pm

Please be positive and constructive with your questions and comments.