Serial two digit display


I am working on a project to keep track of a freezer temperature and send a text if there freezer looses power or if the temperature raises above a certain level. It is all going well. But I am thinking now I wish I had of put a small display to view the temperature.

I have already had a PCB made and everything is soldered into place, and adding the display isn't worth getting a new PCB made, so I thought I might use the serial connections I broke out for programming, and that runs off of 3.3v.

I tried google, but all I can seem to find is larger 2x8 displays or seven segment displays. Are there other options?

Is this what you are looking for?

I don’t think you are going to find a serial display down in the 2 digit range - all the two digit ones I have seen (and like LarryD’s link) are simply multiplexed displays where you need basically 9 wires - 7 for the segments and 2 for the digits. There are some smaller LCD displays that are as you found 2*8 or bigger (that would allow you to display current temp, last high and last low or whatever extra info you wanted to display - always fun to add features until you run out of program memory :slight_smile: )

Maybe wire up a hand wired, one time, board that reads serial and outputs to the 2 digital seven segment.
Put it into a small box.

The TM1637 4 digit 7 segment display (aka grove 4 bit display) is a good choice. It's real small and only needs 4 wires (2 for power, 2 for data).

This display doesn't need you to add all the extra resistors as it has internal power management and works at both 3.3v and 5v.

Also the TM1637 library will make your project a whole lot easier since you need only a few lines of code for it to do what your project needs.

You don't have to use all 4 digits, but if I were you I would use the extra digit to display temperature unit C or F :slight_smile:

Pretty cool little gadget. Had not seen those before (although they show out of stock). I guess there is enough demand for them.

thanks, I will give that a try

Pretty cool little gadget. Had not seen those before (although they show out of stock). I guess there is enough demand for them.

Pretty cool indeed :slight_smile: I use them for most of my projects (timer, clock, distance measurement, temperature and humidity, voltage measurement etc). The main reason I use this is because you get rid of all those wires and resistors which is both convenient and will free up most of the arduino I/O pins and also because the unit has a built in controller so that along with the use of library only a few lines of code will get your work done. Also packs cools features like brightness controls and easy to use alphabets and ":" unit.

You could always get one from eBay or Amazon or Ali express or Banggood of DX or SeeedStudio(grove). I bought mine from ebay and it was a cheap chinese clone "Catalex" and cost me about $3. Using it 24/7 continuously for a few months and so far so good.

thanks, I will give that a try

You could always use the extra display segments to display temperature unit like this