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Topic: Arduino Uno R3: What is the maximum output amperage? (Without damaging board) (Read 28273 times) previous topic - next topic

Arkafan

I did not find this statistic on the Arduino main website.

I am doing a project in which multi-colored LEDs are wired in parallel (each color gets a port, same port for all LEDs) which means I am using 3 digital output ports. (One for R, one for G, one for B (RGB)).

Each LED draws 30 mA. As I am typing this, 3 LEDs are glowing normally.

What is the maximum amperage I can draw through the Arduino Uno? Will I burn the board if I have 15 LEDs?

Thanks,
Ark

nickgammon

Summary:

http://www.gammon.com.au/uno

The datasheet is the final reference, but my link above should be close enough.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

Arkafan

Thank you.

Looks like the Uno itself won't suffice, but I can always program it to run a power supply and/or transistor.

Thanks,
-Ark

nickgammon


Each LED draws 30 mA. As I am typing this, 3 LEDs are glowing normally.

What is the maximum amperage I can draw through the Arduino Uno? Will I burn the board if I have 15 LEDs?


Code: [Select]

15*30 = 450


That exceeds the maximum for the chip, plus you are drawing more than the recommended amount per pin. A few transistors might be in order.

See datasheet, page 314:

Quote

Although each I/O port can source more than the test conditions (20 mA at VCC = 5V, 10 mA at VCC = 3V) under steady state conditions (non-transient) ...   Pins are not guaranteed to source current greater than the listed test condition.
Please post technical questions on the forum, not by personal message. Thanks!

More info: http://www.gammon.com.au/electronics

efifi

Hi

My first post.

I just bought an UNO as well as some adafruit led strips.

The led strips advise the following current current requirements

60 NeoPixels × 20 mA ÷ 1,000 = 1.2 Amps minimum - not all leds on, or dimmed
60 NeoPixels × 60 mA ÷ 1,000 = 3.6 Amps minimum - all leds on bright

Not having a clue what i was doing, i proceeded to plug a strip with 120 leds into the 5+ VCC and group pins of the UNO.

By all rights this should be drawing 7.2 Amps - 120 * 60.

All leds are on full brightness - how is this even possible without damaging the UNO?

I did this for 2 weeks, until I did more reading - now i am terrified to plug the strip back into the ardunio - of course this poses the next problem - a 5V power supply with 10 Amp - but thats another story.

I would like to understand why the leds worked and what i am doing to the arduino.

thanks for your help and patience.

Thanks

Clive
"If I have seen further than others, it is because I have stood on the shoulders of giants." - Isaac Newton

You are my giants........

CrossRoads

The neopixel are powered from the 5V header pin, yes? They only receive signal from the 328P, so no damage there. Kinda surprised you didn't smoke the 5V regulator, which is only rated for 800mA.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

JimboZA


The neopixel are powered from the 5V header pin, yes? They only receive signal from the 328P, so no damage there. Kinda surprised you didn't smoke the 5V regulator, which is only rated for 800mA.


That was going to be my question: assuming the LEDs are only controlled, not powered, by the I/O, what current can the board supply at the 5V pin.... the OP seems an order of magnitude over the allowable so that regulator must be glowing.
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Your answer may already be here: https://forum.arduino.cc/index.php?topic=384198.0

efifi

Thanks for the rapid response

Correct - The neopixel are powered from the 5V header pin - the data pin sends the signal.

"Kinda surprised you didn't smoke the 5V regulator, which is only rated for 800mA." - so, i guess I should thank my lucky stars I got away with this and not try it again.

The question still remains - how did i get away with it? It indicates the regulator has a massive tolerance

"If I have seen further than others, it is because I have stood on the shoulders of giants." - Isaac Newton

You are my giants........

CrossRoads

No idea, unless it is not drawing the current you think it is.
The reverse polarity protection diode is only rated for 1A, seems kind of unlikely that both devices would survive an overcurrent condition like that for so long.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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