Hello. I am working on a project that involves displaying some numbers such as temperature on the display.
As a reference we can look at this product:



Requirements:
1. Ultra low power display
2. Ultra low power processor to read the temperature
3. Battery powered device, ideally 1+ year on a small battery

Ideally the numbers displayed on the display would be in white color other than black. (Most display seem to use black color such as the one below):



I dont have much experience with the displays. My questions are:

How to choose display for project such as this one? What type of display draw least amount of power and are most suitable for battery powered applications?

Since this is a very simple device, I am not sure what type of CPU would I need for measuring the temperature. I think event the most basic STM32 is an overkill for this task.

 

What is wrong with the low power temperature displays that you have shown?
You cannot do better that those.

 

What is wrong with the low power temperature displays that you have shown?
You cannot do better that those.

There is nothing wrong with the temperature displays I have shown. I am working on a project to create my own temperature display that would be as much energy efficient as possible.

It does not have to be better than the ones I shown. In fact it most likely will be much worse but that is fine.

In terms of CPU, I figured that it does not get any better than EFM32 microcontroller such as:
https://www.silabs.com/documents/public/data-sheets/efm32hg-datasheet.pdf

The result is not as important as the process through which I am going to learn many things.

The most tricky part for me seems to be the display I guess.

 

Fair enough. If you want to learn to DIY a low power system you can have a look at my 10000 year clock project.
Average current draw is 3μA.

https://forum.allaboutcircuits.com/ubs/long-clock-prototype.647/

 

Fair enough. If you want to learn to DIY a low power system you can have a look at my 10000 year clock project.
Average current draw is 3μA.

https://forum.allaboutcircuits.com/ubs/long-clock-prototype.647/

Dang thats cool.

How do you even measure currents as low as 3uA.
As far as I am aware most digital multimeters cant even do that!

 

Why do you think you need a 32-bit processor to read and display a temperature? An 8-bit PIC would be my pick.

 

Why do you think you need a 32-bit processor to read and display a temperature? An 8-bit PIC would be my pick.

The reason I picked efm32 is because I thought they would be somewhat simillar to STM32 which I have used many times before unlike the PIC microcontrollers (never used them).

Are there any obvious benefits of choosing an 8 bit PIC versus an 32 bit microcontroller such as EFM32. Lets assume the price is the same.

 

Far simpler board design and probably lower power.

 

Look into the type of e-Paper displays used for price tags in stores. Waveshare makes a large range and the example includes red but there are other options from simple black and white, to 4-level grey scale, to 16-color palette.

​

The price tag shown in the photo uses NFC to identify the particular tag and it communicates using Zigbee. Amazingly, though, there are e-Paper displays that are entirely powered by NFC and can be changed by an ordinary NFC write to the module.

 

I should have mentioned that e-Paper displays consume zero power unless updating.