Charging from a battery

Hi everyone,
I am working on a project that has just an Elegoo Nano, a small SPI screen and a DS3231 to remember the time.
The idea is that I have a single button that turns on the board, generates a QR code and shows it on the screen and then shuts down after 10 seconds.
I was looking for a way to make my Arduino shutdown after 10 seconds and this is the best solution I've found: http://www.zolalab.com.br/img/zolalab_shutdown_relay.jpg.
Now, I see that that circuit is supplying energy through the 5V pin and not the Vin.

My questions are:

  • Is that circuit a good solution to auto-shutdown an Arduino or do you guys know of a better one.
  • Where do I even get a 5V power source? I cannot find anything online and if I use just AA batteries I can only get 4.5V or 6V which is not good, since I read that to supply the board through 5V you should give it a maximum of 5.5V.

I am pretty new at using microcontrollers and don't have much experience with electric parts in general so please forgive me if my questions might be stupid.

Thank you!

Hi,
Welcome to the forum.

Please read the first post in any forum entitled how to use this forum.
http://forum.arduino.cc/index.php/topic,148850.0.html

Try using a 5V USB power unit.

Its ideal for your application.

Tom... :slight_smile:

Hi Tom,
thank you for the welcome.
I cannot use a socket to power this project, it has to be standalone so it has be powered by batteries.

Use a switching buck regulator from an appropriate battery? Check the required current for your system, but I would guess that 50-100 mA should probably cover it.

Or perhaps a USB power bank?

As far as I can tell, that circuit should do the job of auto shutdown (with the right code), though I'm not quite sure why it's switching GND rather than Vcc. A proper circuit diagram might make things clearer...

lastxtemplar:
and if I use just AA batteries I can only get 4.5V

It should work fine on 4.5v from a pack of 3 x AA alkaline cells.

...R

Hi there
a while back bought a few cheap usb powerbanks to use with a arduino project but after i press the On button to start it, it turns off after 10sec -+ if the load are too low.... making it unusable for what i had in mind but maybe something like that would be perfect for you??
just a thought

Best of luck

Have you considered sleeping? Otherwise you're going to need analog circuitry to time 10 seconds.

Can a phone scan the QR on that screen? Can you show which screen you have?

Robin2:
It should work fine on 4.5v from a pack of 3 x AA alkaline cells.

...R

I saw some people using these batteries so I got them, waiting to be shipped.
I did notice however, now that I added the relay to the circuit, that the relay tends to not work half of the time, I think the whole circuit is draining too much energy. Another notice is that if I just draw a full black background on the screen the relay works everytime (my screen always has a white background).

INTP:
Have you considered sleeping? Otherwise you're going to need analog circuitry to time 10 seconds.

Can a phone scan the QR on that screen? Can you show which screen you have?

Yes, I did consider using sleep but from what I understand the board still drains power when sleeping so I think that turning it off completely is the way to go.
I am using this screen and yes, surprisingly my mobile app sees the qr code really fast :slight_smile:

lastxtemplar:
I saw some people using these batteries so I got them, waiting to be shipped.

They will give 4.8v which is fine. But if you are thinking of charging them while connected to the Arduino you must check first that the charger voltage does not exceed 5v

I did notice however, now that I added the relay to the circuit, that the relay tends to not work half of the time,

Without seeing the circuit diagram I can't comment.

...R

Dear zola lab,
Any developer that uses a fritzy for technical documentation of a product or method is dubious best.