I want to make a small 3 channel relay board which can be control wirelessly. using a arduino uno would be overkilled because I just need 3 pin from the micro controller to control it. So my obvious choice was this tiny fully functional MCU Attiny85. It is small and compact and the best of all it does not require any passive components to run. so I go with this one.

The pinout for the ic given below,

But in order to program the IC we need an Arduino Uno board. Connect the corresponding pins as shown below so that we can use Arduino as ISP,

After programming the IC is ready to use. Sometimes depending on the IC you might need to flash the bootloader before uploading the code.

So after that was done I need to communicate to the board wirelessly. So I use HC05 Bluetooth module to talk to the board And send commands from my smartphone.

After adding the relay circuits the full schematics is looks something like this

now I made a PCB so that I can mount all the components on to it.

Thanks PCBWAY for the support.