Maker Pro
Maker Pro

arduino digital pin output power question

Status
Not open for further replies.

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
so I read on google, that the output of a digital pin is 20ma continuous current.

Is that for just one of them on at once, or is it 20ma for them all on at once? (I need 16 outs.)

Is it less for more of them?
 

kellys_eye

Jun 25, 2010
6,514
Joined
Jun 25, 2010
Messages
6,514
No - 20mA is what the digital port can SOURCE. It's not 'continuous'. The 'total' permitted depends on the maximum power dissipation of the package - check the datasheet.
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
Thank you for the answer Kellys_eye. Can u please give me one more bit of help.
So can u give me a guess for how many amps you can put out of 16 outputs?
 

bertus

Moderator
Nov 8, 2019
3,304
Joined
Nov 8, 2019
Messages
3,304
Hello,

The R3 has 14 digital i/o pins
Read the technical specs on this page:

Bertus
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
The guy on that page, funnily; is asking the exact same question as me. WHAT A COINCIDENCE!!!
 

danadak

Feb 19, 2021
751
Joined
Feb 19, 2021
Messages
751
From datasheet :

1680626309636.png

Per pin 40 mA, total of all pins 200 mA.

And the port limitations :

1680626400271.png

Notice the difference between source and sink limitations of the port.


Regards, Dana.
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
So this means, the more outputs you use the less current goes through them?
 

danadak

Feb 19, 2021
751
Joined
Feb 19, 2021
Messages
751
Not exactly. It means there is a total limit to the current you can pull thru
internal busses, each port having a buss, and the chip the sum of all busses.

Its not that a GPIO pin has less drive capability, its the V drop on these internal busses
causing internal logic errors, also the currents flowing in localized internal substrate areas
causing issues for logic operation.

And there is a difference in GPIO sourcing current, hence that current flows thru internal
buss, versus sinking current, dumping current into the substrate. Lots of crazy effects
can occur in operation of the internal transistors.


Regards, Dana.
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
That sounds fairly serious, so if u plugged in 16 parallel outputs, what resistor would u use for 5 volt?
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
Just say its just a wire, it should be load free, I just need the most minimum resistance I can for the equivilent of just running down a wire.

(u can run a motor like this, if i go to a battery, i can actually short the battery away from the motor.)
 
Last edited:

danadak

Feb 19, 2021
751
Joined
Feb 19, 2021
Messages
751
Not sure I understand. You paralleling outputs to supply power thru a wire ? If so
how distant the load, and AWG of wire you will use ?

If so why not just a simple external switch activated by one GPIO pin ?


Regards, Dana.
 

dragon

Oct 31, 2022
248
Joined
Oct 31, 2022
Messages
248
It may be a little wierd... but...
Im actually going to a battery that is running a motor at the same amps as whats going to come out of the arduino. (so its not amped) but theres no load because im actually just causing the battery to go in series with the arduino output, instead of the motor.

I hope it doesnt blow it up, but it seems to work in falstad.

Anyhow if that works its actually the start of my capacitor amplifier, but if u want something similar that u can understand, its kinda like going to the base of a transistor, so its loadless, and I just would like to know how much amps Im allowed if i did it on 16 parallel outputs.

I can just find out, but I was wondering if u could give me a guess in advance, and I might get it wrong, so more advice the merrier.
 

Bluejets

Oct 5, 2014
6,901
Joined
Oct 5, 2014
Messages
6,901
It may be a little wierd... but...
Im actually going to a battery that is running a motor at the same amps as whats going to come out of the arduino. (so its not amped) but theres no load because im actually just causing the battery to go in series with the arduino output, instead of the motor.

Yes, weird would be one explanation.
I fear my head would explode if any of your reasoning made any sense.
 
Status
Not open for further replies.
Top