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## Building a Standalone Temperature Logger: Part 7

Welcome back! In this part we’ll explore how we can reduce our power consumption which will allow us to move from 2 AA batteries to a 3V coin cell.

When the whole circuit is operating in logging data mode and at 2.68 volts, it’s taking up 1.06mA. First off this 1mA is much lower than our assumed 2-3mA because we are running at 3V instead of 5V, less voltage means less power consumption. Using the Battery Life Calculator with a 240mAh battery it gives us a estimated battery life of 8 days. Lets see how low we can get our power consumption to!

## Building a Standalone Temperature Logger: Part 5

Welcome to Part 5, in this part we’ll talk about enabling brown out detection to our Standalone Temperature Logger as a safety mechanism. The information below about brown out detection is also available as a video explanation, I recommend viewing the video whilst reading below.

Before we do anything let’s take a look at the ATtiny85’s datasheet, we want to check what voltage range works on.

## Building a Standalone Temperature Logger: Part 1

I plan to build a Standalone Temperature Logger with the minimum components as I can, I’ll be using the ATtiny85 and Arduino software to program it. Firstly I’ll have it run on the Arduino to confirm it’s working, then migrate it to the ATtiny85, make it run on battery and make a PCB of it all. It sounds like a simple concept, but I know there’s going to be more to it that meets the eye.

Design Characteristics

• Use the minimum components possible
• Power the project with batteries
• Specify the logging delay time
• Write temperature to EEPROM on-board
• How to extract data from EEPROM

Now lets go through all these design characteristics.

## Reading data from EEPROM I2C on a PCB

I thought I’d look into reading data from an EEPROM that is I2C capable from a PCB, the PCB is from a KVM which is a device that allows you to use your keyboard, video (monitor) and mouse on different PCs without switching out the cables.

Below is the PCB and the EEPROM which we’ll be looking at.

If you can make it out it’s a Atmel 24C32A, a 32Kbit EEPROM, datasheet here: atmel 24c32a