Arduino does not work without USB

Hello, guys

Please help me out.

I am trying to use the Arduino Uno V3 to work with external power supply of around 5v.

However, after uploading the code into the Arduino board, it seems the Arduino does not work at all with my external power supply.

The green LED is light but the L LED keeps blinking quickly which seems a bit weird.

The code should be ok cause it works perfectly when the USB is connected.

Could anyone give me any suggestions?

Thank you all.

To what did you connect the 5V ? What is around 5V, could it be 8V ? Some cheap wall warts have a high voltage without load.

By the way, the version is called 'R3'. All 'R3' boards and shields work together.

Peter_n: To what did you connect the 5V ? What is around 5V, could it be 8V ? Some cheap wall warts have a high voltage without load.

By the way, the version is called 'R3'. All 'R3' boards and shields work together.

Hi, thanks for replying me.

I am connecting 4 AAA batteries to the pin Vin.

I am afraid the voltage cannot be higher, as some requirements of my project.

Yes, I am connecting my wifi shield with the Arduino Uno R3.

Any idea why the board does not work with my external power supply?

The regulator on the Uno requires 7 to 12 volts and your 4 x AAA is only giving 6 volts.

Martin-X:
The regulator on the Uno requires 7 to 12 volts and your 4 x AAA is only giving 6 volts.

Thanks for your reply again.

The batteries are not fully charged, so giving around 5V measured by multimeter.

Is there any method to get rid of the regulator? I think I have read this method from the Arduino website, but cannot really understand what exactly I should do with it.

Could you please give me any help with it?

Thanks.

If you accept the risks then connecting to the 5V pin is the easy option. A web search will show a load of differing opinion on this, take your pick.

If you really need a battery powered device then make a stand-alone, that's when the fun really starts :)

Martin-X: If you accept the risks then connecting to the 5V pin is the easy option. A web search will show a load of differing opinion on this, take your pick.

If you really need a battery powered device then make a stand-alone, that's when the fun really starts :)

Oh, right, I'll try it out.

Thanks alot!

Martin-X: If you accept the risks then connecting to the 5V pin is the easy option. A web search will show a load of differing opinion on this, take your pick.

If you really need a battery powered device then make a stand-alone, that's when the fun really starts :)

Hi, I tried it out. The L LED stops blinking, but the code is still not running.

For the coding, I am trying to make the Arduino takes measurements from pin A0 and A1 and save the data into a inserted SD card on Wifi shield.

This piece of code works when connected to PC by the USB cable, but once batteries are used, I find no measurements are written into the SD card.

Do you have any idea why it does run the code well?

Thank you

Most likely there's not enough power left in your already depleted batteries. It's a no-win situation because fresh batteries will be over voltage.

Martin-X: Most likely there's not enough power left in your already depleted batteries. It's a no-win situation because fresh batteries will be over voltage.

Now, I am connecting the batteries to the boost converter and then to the Arduino.

Measured by the multimeter, the voltage comes out from the converter is 5.11 V and the current is 0.35A around.

On the Arduino, only the green LED is light, but when I check the SD card, there's still nothing written into there.

What else can I try to solve this problem please? I really no idea why it still does not work.

5.11V to VIN pin ? That is not enough.

Peter_n:
5.11V to VIN pin ? That is not enough.

Oh, no, to the 5V pin.

By the way, I found blinking LED code could work properly, just does not work on writing data into SD card.

Problem solved, I went to bought another 4 AAA batteries and connected them to pin Vin. This time, it works.

I guess the voltage was enough but too less current in my previous batteries.

Thanks guys for your advice, really appreciate.

But... but... but... 4 AAA batteries to VIN is not good at all. It might work, but for how long ? 10 minutes ? 1 hour ?