Introduction: IR Wireless Temperature Sensor With ATtiny85

About: I'm student in The University of Sofia (St. Kliment Ohridski) in Bulgaria. I have a lot of interests, most of them are related with electronics,pc and programming.

Arduino is simple and very powerfull open source/hardware platform where only your imagination can stop you.A few days ago I read an instructable that inspire me to do my own.The instructable is about how you can send strings of data from one arduino to another.Everything is ok but I wanted to make it with Attiny85 .but unfortunately libraries are not supported with this microcontroller.So, I need to find a way how to generate 38khz and send modulated data and how to translate those data.I'm not enough pro :) to know how attiny85 to generate 38khz itself so I used old good one 555 timer.Everything is good but now I must to send data somehow.There are 3 possibilities:

1-By controling reset pin of the 555 timer

2-switching on/off power supply of 555 timer

3-switching on/off LEDs(timer is always on)

I used 3th variant.

Let's start!

Step 1: Parts List

Microcontrollers and timers:

1x555 timer

1xATtiny85(you can use any microntroller from Attiny family)

Resistors and trimers/pots:




1x10k trimer/pot






Any pnp/npn transistors.In this project I used 1xBC547(npn) and 1xBC327(pnp)


LM35DZ couse it's easy to use



LEDs and transmitters:

Any IR leds.

You can use any ir receiver.Why??Because you can tune to the right frequence 555 timer with 10k trim/pot.


*To be exactly 38khz you must to tune trimer/pot around 7.979k or just mesure frequency with multimeter

*Supply voltage can be everything between 6.8v-30v
*Attiny85 is running at 16mhz internal oscillator

Step 2: Shematic and Pinouts

Step 3: Transmitter Code

After you finished with circuit you must to upload some code..right? :D

In my project I used morse alphabet to send data.

There are two files, first one is little modified Morse library and the second file is main program.
I uploaded the code trought Arduino with tiny cores.
You can find it here:

Step 4: Receiver Code

It can be done a lot of optimizations.Because now you can only send numbers(in my case temperature).

Step 5: Update

Couple pictures how I integrated this circuit.

Step 6: Final Product

Basic characteristics:

Next goals:

Single chip solution, less power consuption
Please comment and share your ideas for improving this device.
Thanks for reading!

btw: English is not my native language so sorry for mistakes and etc.

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