For RTC clock I use DS1307 homemade module, but works without changes with DS3231 module.
For thermometer and higrometer it use DHT11 sensor, but with a small change in sketch can be use DHT22 (AM2302) sensor.
I use led display named LFD080AAG-103-01 (4-digit 7-segment common cathode).
"Brain" is Arduino Nano with ATmega168 microcontroller, but work wery well with Arduino Nano with ATmega328 or Arduino Uno board.
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Step 1: Schematic
1) Arduino Nano board with ATmega168 chip (work also with Arduino nano wih ATmega328 chip or Arduino Uno board)
2) led display named LFD080AAG-103-01 (4-digit 7-segment common cathode)
with small changes in sketch work with common anode display
3) RTC module (homemade or buy-it) with DS1307 or DS3231 chip
4) DHT11 sensor (work with small change with DHT22 or AM3231 sensor)
5) 2 push button
6) 5V active buzzer (1kHz or 2kHz), I use for test red led & 330R resistor
8) some Dupont wire
9) usb cable
10) 5V usb power supply
Step 2: Sketch
I write an sketch named multiplexedclock4_3.ino who can use for common cathode or common anode led display, just activate or deactivate some lines.
It use just 2 button, one is named ADJUST for enter in adjust mode, and second buton is named "+" because increase value until maximum, after changed value is put to minimum... value increase slowly by press repeatedly "+" or value increase quicly by push and hold down "+" button.
Step 3: Video
Is more easy to undertanf who work and how can be adjusted value be seeing the video...
Step 4: Normal Operation and Adjust Mode
Usual, on display is time (clock) about 5 seconds, temperature about 1 second and relative humidity in air about 1 second.
If you push on ADJUST button, clock enter in hour adjust mode (xx.CL style).
If push shortly or hold down the “+”button value fro hour increase (after 23 is reset at 0).
To exit in minutes adjust mode, must push ADJUST button… on display you will see CL.yy format.
If push shortly or hold down the “+”button value fot minute increase (after 59 is reset at 0).
For exit from minute adjust mode and enter in next menu, must push ADJUST button. On display is AL.on or AL.oF, in this case is AL.on (alarm is activate) and after push “+” button you will see AL.oF.
If alarm is deactivate (OFF = AL.oF) and push ADJUST button, system enter in usual mode, as clock with temperature and humidity indicator.
If push again ADJUST button, system enter again in hour adjust mode
and you can change hour value with “+” button
Exit in minute adjust mode with ADJUST button
Push “+” button to activate alarm
Now, if I push ADJUST button system enter in hour alarm adjust mode
and value chen be change with “+” button (push or hold down). After that, I push ADJUST button to enter in minutes adjust mode
If push “+” button value for minutes increase and when push ADJUST button system enter in clock mode.
In right side decimal point is on when alarm is activate and off when alarm is deactivate. When is time alarm, active buzzer (red led in my case) is intermittence active.
In time alarm, if you push “+”button alarm is temporary deactivate (until next day)....
For extra info see: