DIY Digital Thermometer




This instructable will show you how to make a thermometer that displays the temperature of the air.

It's not the most accurate thermometer in the world, but for this price and the fact that it was homemade...

Step 1: Parts

You will need:

1x ATMega8
2x7 segment display
1x1800 ohm resistor
7x160ohm resistors
1x KTY-13-5 (temperature sensor)

Step 2: Circuit

I tried to make the circuit as simple as I could without over complicating the program.

Step 3: Software

You can change the resistor you use with the sensor and the formula for calculating the temperature if you got a different sensor.

Step 4: Uses

Now you might wonder where you could use this thermometer.

You can use it in your computer, but you should have plexi glass.
You could also use it for measuring the temperature in a room.
And what about putting it in a greenhouse and monitoring the temperature?

You should just remember that it isn't very accurate.



    • Faux-Real Contest

      Faux-Real Contest
    • Cardboard Challenge

      Cardboard Challenge
    • Warm and Fuzzy Contest

      Warm and Fuzzy Contest

    39 Discussions

    Vitor Reppen

    3 years ago on Introduction

    The board is damage on eagle, can you replace it with a good one ?
    Or just send the diagram on eagle.

    I am just curious if this kind of thermometer can measure the temperature of a human body?

    J. Davis


    4 years ago on Introduction

    can you share ATmega8 end ATmega8L Fuse bits?


    8 years ago on Introduction

    I cant seem to find the sensor chip anywhere, is there any other name for it? Can you send me a link for where i can buy it from? Thanks.

    2 replies

    5 years ago on Introduction

    Hello , Have a good day ...

    I'm interested in this nice work , I want to know How to record the results on memory card similar to what existing in the mobile phones and please send me the diagram or sketch for that ?

    Sincerely , ...


    6 years ago on Introduction

    I want to build a thermometer. I can not download the hex file to operate. Can anyone help.
    thank you


    9 years ago on Step 2

    I've been trying to build this circuit and I had a number of questions. Does a ATMega8L work? Do you need to program this? I was wondering what "This part is optional" meant? Does this mean connect all of this together? I was trying to order the KTY-13-5 temperature sensor. The KTY135 surface mount temperature sensor kept popping up. This is extremely small and hard to use. Do you know of an equivalent sensor that is much easier to use? What does the Vcc arrow connect to from the diagram? What does GNDIC1 mean? And as for power, is 1 positive? I'm excited about this project. I'm hoping to get it to work. Any help would be much appreciated.

    2 replies

    Reply 9 years ago on Step 2

    I think that a ATMega8L should work and yes, you need to program it.

    That optional part is for connecting a programmer, so you can program it.
    I didn't mark the pins in the schematic, but they are like this (from 1 to 5): POWER, MOSI, MISO, SCK, RESET, GROUND.

    The pins above are the pins from the programmer. I personally use the STK200/300. You can also buy an avr ISP programmer.

    I know the sensor is surface mount. When I ordered it, I didn't know. Luckily I managed to solder it. I guess you could use any sensor of the same family. Check the datasheet, there are more models inside. They all change their resistance with temperature and use the same formula to calculate the temperature. The only thing you might need to change is the resistance at 25°C (it's in the source code (i think the name of the variable is r25)).

    It was not the best idea to add both the power symbols and plugs into the schematic, it only makes it confusing. The Vcc arrow is supposed to indicate that a 5V power supply is connected to that wire. The GNDIC1 is normal ground (eagle named it like that).

    Yes, pin 1 of the plug is positive.

    I hope you'll make it. If you have any trouble, don't be afraid to ask. If I don't answer in a while, write me a PM.


    Reply 6 years ago on Introduction

    actually i m new in electronics.there is a symbol of ground in the diagram the problem is that i dont know where to connect that wire plz help


    6 years ago on Introduction

    Great tutorial, just one question: so you said its not very accurate, is it due to the sensor used or just the design itself?


    7 years ago on Step 3

    cool project!! Now, i'm trying to build it , but i'm not able to program C. If i use a LM35 sensor what is the formula for calculate the temperature? What resistor i have to use ?


    Reply 7 years ago on Introduction

    Its a ATMEL mega chip. This usually comes with the arduino platform. ( arduino uno ATM 328. the chip is ATM (atmel) 32 bit 8 ) ref:


    9 years ago on Introduction

    if ur saying its not that accurate, how should i think of that? like 5 degrees(celcius) or less than 1?

    1 reply

    9 years ago on Introduction

    is there a way for this to be Fahrenheit? im no good at interpreting Celsius.. or programming microchips for that matter. never mind lol.

    1 reply