Guide for power supply to ATMega328 and SIM800L project

[dakshsaraf]

I am creating a Data Logger that uses:

1. ATMega328p - Microcontroller
2. SD Card Module to read write data
3. SIM800l - Modem to transmit data from SD card to API
4. OLED I2C Display
5. DHT22 Temperature sensor

I want to power all this using 4 or 6 AA batteries. I do not have much knowledge about power electronics.

• As ATMega328p needs 5V, I think the batteries should suffice. But the Voltage output from AA batteries degrades over time and fluctuates so do I need additional circuitry to control the input to the ATMega328p?
• The SIM800 needs a 4.2V input. But while transmitting its causes a voltage drop and current bursts up to 2A. For that I am using the power circuit given on the datasheet.

So what I wanted to understand is that can a 4-6 AA battery bank be sufficient for this project. The ease of replaceability of the batteries is very important. The batteries should be cheap and easily available at local stores, hence the choice of AA batteries.

Would I need additional circuitry to supply power to the ATMega328 and other components as well or directly from the battery bank should suffice?

[ShermanP]

The ATMega328P doesn't really need 5V. Even at 16MHz, 4.2V should be enough. If you run it at 8MHz, Vcc will work down below 3V. So you have a lot of flexibility there. I think the same should be true of the DHT22, at least down to 3.3V. The typical microSD card module has its own 3.3V regulator because the card is a 3.3V device. But the regulator may have a large dropout voltage, so 4.2V feeding that may not work well. So you may need a better regulator for that part. I don't know what your display will need.

I don't know about the SIM800, but I thought that was a 2G part. Anyway, it would be convenient to power everything at 4.0 - 4.2V, which should work if the display will work at that voltage. But a switching regulator might work better for battery life.