Need help: Atmega328p, DS1307z RTC and 0.84" 96x16 OLED powered by CR2032


I need a bit help because I’m not sure I made everything as I should. And I’m not sure it will even work or not as it is. So the idea is to make a small authenticator (login code generator) for webpages. I already made a prototype with arduino but it’s too big even with a nano so I decided to make my own. What you need for these are an RTC with the server time and a unique device id (and a bunch of code). To make it more power efficient I want to run the Atmega328p at 8Mhz, use a switch to only turn it on when the button pushed and use a CR2032 3V coin cell to power it. I use Atmega328p because the code part is really big and I wanted to make sure everything will be fine and there will be no memory overflow. The OLED display can be powered from 3V so it must work. This is my first PCB design and my first standalone Atmega, so maybe there will be problems. Thank you for your help, and if it work out then I share the whole project.


ER-OLED0.84-1_Series_Datasheet.pdf (792 KB)

DS1307.pdf (348 KB)

:frowning: I doubt you'll get much battery life, if it works at all...

Have you tried powering your prototype from the coin cell?

Do you have a multimeter to measure the current and to measure how the battery voltage is holding-up?

The [u]specs[/u] i found say the 2032 is rated at 240mAh, which means after 10 hours at 24mA (like maybe powering a couple of LEDs) you'd be down to 2 Volts... Or at 500mA, you'd be down to 2V in a half-hour.

Resolution on those schematics is not quite good enough.

There is not enough supply decoupling. There should be a 0.1uF cap on the Aref input as well.

The reset line needs a 10K pull up resistor.

The display says the maximum voltage for the logic is 4V, you seem to be feeding 5V into it.

Thank you for answer. I made the arduino one powered from usb and I have a LightBlue Bean which powered by CR2032 and I tried the OLED screen with that without the RTC. So if the CR2032 wont be enought I try something else. Maybe I use only the CR2032 to feed the RTC standby and make it like a pendrive to power it from usb. Thank you Grumpy_Mike I modify the schematic!