Picture of 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)
Vitor Reppen2 months ago

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

CatherineDavis10 months ago

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

J. Davis


cocok11 months ago

can you share ATmega8 end ATmega8L Fuse bits?

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.
Also is the 7 Segment Display and Anode or a Cathode one?

that should be a common cathode display.

mnedal2 years ago
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 , ...
tot542 years ago
I want to build a thermometer. I can not download the hex file to operate. Can anyone help.
thank you
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.
DemonDomen (author)  circuit_question6 years ago
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.
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
ertxz183 years ago
Great tutorial, just one question: so you said its not very accurate, is it due to the sensor used or just the design itself?
finalxxx373 years ago
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 ?
Gernerakos4 years ago
What is the ,,ATM mega 8
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: http://arduino.cc/en/Main/ArduinoBoardUno
which supply voltage?
godofal5 years ago
if ur saying its not that accurate, how should i think of that? like 5 degrees(celcius) or less than 1?
DemonDomen (author)  godofal5 years ago
I think it's something like +/- 2°C
A.C.E.6 years ago
is there a way for this to be Fahrenheit? im no good at interpreting Celsius.. or programming microchips for that matter. never mind lol.
DemonDomen (author)  A.C.E.5 years ago
Sure, you'd just have to convert the number, but you'd need 3 displays.
diydept6 years ago
Very nice 5*,This capacitor is very familiar to me. Is it Iskra Slovenia?
DemonDomen (author)  diydept5 years ago
Sure is.
achelblack5 years ago
hi.i went to the store today to purchase the atmega8..but they asked me 'what number?' and i didnt know what to say..help me please..what did they mean by that?
from the picture he posted i see that he is using an ATMEGA8-16PU so thats wat u can buy
achelblack5 years ago
hi..can i ask sumthing? can i use any type of atmega8 for this project?
pipp5 years ago
ooo you used iskra capacitators :D i haven't seen them in years (and this is the first time on instructable)
Livyo5 years ago
It's work whit an DS18B20 sensor ?
thats brilliant im going to radio shack soon so how much did all the components cost
circuitmage6 years ago
How 'bout a shot of the back of the board? :)
circuitmage6 years ago
Nice project. Gets a vote from me for application. +/- 1 deg accuracy is a must for work applications. I need to build one for work to check IC temps. Check my entry for similar display project!
odiekokee6 years ago
What is your total component cost for the project?
DemonDomen (author)  odiekokee6 years ago
I think it is safe to say that I paid about 15€. But you should know that I had to pay something like 5 € for the avr -.-
PKM DemonDomen6 years ago
Is that under the normal price? It certainly doesn't sound like much for a large uC.

Do you know how much heat the temperature sensor will stand up to? I'm looking for a circuit like this to monitor the running temperature of my (air-cooled) motorbike engine, but can't use a temperature sensor that will melt as soon as it hits 90oC.
DemonDomen (author)  PKM6 years ago
I checked on ebay, they cost 1,50€. The datasheet says it can survive up to 150°C.
PKM DemonDomen6 years ago
OK, cool, that's good to know. Still need to get set up with a programmer, stripboard, common components etc. Hey, how do you get euro symbols? When I try to put the sterling symbol, the site goes mad and won't let me post comments.
DemonDomen (author)  PKM6 years ago
I just press Alt + E. If you want to make your own programmer, you should build the STK200/300. That's what I'm using and so far it worked quite well.
Kiteman6 years ago
Nice little project. You say it is "not very accurate" - how close to true is it? Also, quite a few people would find it useful if you included a layout for soldering the perf-board.
zaketus Kiteman6 years ago
With that thermistor accuracy would be about +-3% in 25C (about 75F) temperature. Accuracy might vary with different sensors or packages.
DemonDomen (author)  Kiteman6 years ago
I'll try to check the accuracy when I find the time. Expect it to be in 1-2 weeks. About the layout... There's a lot of wires under the board, but you can't see it on the pictures. There was no way to make it with less wires. I'll upload a pcb.