This is my first Arduino project, i wanted to make the above using an LM 35 Temperature sensor, an HD44780 LCD, and to reduce costs a ATtiny85, as i am aware through this forum, the ATtiny 85 has limited i/o's so i would like to use a 74HC595N shift register, all this sets a relay with a 5v coil to connect a 12v supply to the Fan motor, temperature controlled by the LM35.
I have now hit the wall and need help, i have started a circuit using Fritzing, but i do not know how to connect the ATtiny 85 with the LM35 and LCD.
Can anyone help me complete the circuit, assuming i am correct so far
What you gain on using a MCU with limited I/O - considering you want the LCD display - is lost on adding extra interface chips like a shift register or I2C backpack. Even if cheaper in terms of chips, you have to consider the complexity of the assembly in regard to chip count.
As goes price, the Chinese ready-assembled modules ("Pro mini" with no integral USB interface) are so cheap (about $3) themselves that it is basically a waste of time to seek the smaller chips.
