How to power arduino only using a plugged in power adapter? (Not working!)

Other Hardware General Electronics
1

Hi!

I have a set up where I try to data log information from temperature sensors to a sd card. When my arduino mega is plugged into the usb port of my laptop it all works. (at least until my laptop went to sleep mode). But when it is only plugged into the 9V power adapter (which is plugged into an extension cord and then a 120V wall outlet) NOTHING happens.

I spent some time googling the problem and am wondering if it is an issue of grounding. Do I need to somehow ground the arduino in that scenario - and how do I physically do that?

Thanks so much for ideas for this newbie!

1 Like
2

yanafrank:
But when it is only plugged into the 9V power adapter...

You forgot to tell us how you have connected this (unspecified) adapter to the Mega.

A 9volt/500mA regulated adapter connected to the DC socket would be ok.
As long as the polarity is right (positive center).
Leo..

3

I would check the power adapter with a meter - you will need a meter anyway for troubleshooting - does not need to be fancy - most any inexpensive digital multi-meter will work

4

Do I need to somehow ground the arduino in that scenario

No grounding in this context means connecting power supply negitave terminals together.
Your problem could be incorrect polarity or the hole in the power jack lead being too big for the pin on the Arduino’s socket. Do any of the LEDs light up?

5

If the Mega's power LED does not light, you probably have a wall wart with a NEGATIVE center pin.

6

Hi all!

First of all, thank you SO MUCH for your attempts to help, I really appreciate it a lot!

One thing I obviously was not clear about: The arduino DOES definitely get power, i.e. the green LED is on. That's why I was so surprised it did not record any data! When I plug my laptop into the usb port (and still keeping the rest of the power setup) it suddenly does work and both shows data on the monitor and records it to the sd card. But when my laptop went to "sleep" half an hour later it said:"Failed". I am totally confused why this is - not even sure if it is a hardware or software problem. (I did NOT reload the sketch, it's the same sketch that either runs or not, depending on if it's attached to the laptop)

I know that this makes me sound pretty stupid, wondering about electricity being the problem if the arduino does appear to get power! But I had read somewhere online that similar problems are sometimes caused by faulty grounding, and that the usb connection through a computer is automatically grounded correctly...

Btw, this is the adapter I am using:

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Dtools&field-keywords=SunFounder+DC+9V%2F650mA+Power+Plug+Adapter+for+Arduino+UNO%2C+R3+Mega+2560%2F+1280+(3+Feet)

Thank you again for any insights!

Yana

7

It sounds like a software problem.

If the LED's are lit on the Arduino when the DC-powersupply is plugged in, that part should be sorted.

When the computer 'opens' the serial port, it resets the Arduino. Maybe this reset made the software go haywire?

// Per.

8

can you confirm that you are(were) using the USB connection only for power and that you don't start the sketch by initiating some Serial communication first ?

9

I got a PM, telling me that i am an idiot, since the regulator on the Arduino cannot drive anything else other than the CPU, some LED's and not much more. I do not agree on this.

You write that you connected some sensors - how much current are these drawing? Unless it's som esoteric old-fashion sensors drawing a lot of power, i can't see that it's the issue here.