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Temperature and humidity sensor
Rebuilding an existing module to be a stand-alone temperature and humidity sensor. Uses an AVR ATmega8 microcontroller.
I/O
Inputs
- PC0 Temperature sensor (analog)
- PC1 Humidity sensor (analog)
Calculations
- Temperature

- Humidity

Outputs
- PB0 Life signal
- PB1 Link activity
Serial communication
D-sub 15-pin
- 13.8V
- 0V
Communication
Interfacing is done with RS-232, using MAX232 or MAX202.
Serial settings
- Baud
- 38400
- Data bits
- 8
- Parity
- None
- Stop bits
- 1
Source code
Gallery
Schematic diagram
Parts used
Qty.
|
Part
|
1 × |
AVR ATmega8-16PU, DIL-28, 16 MHz, 23 I/Os
|
5 × |
Capacitor, aluminium electrolytic, 1 µF, 50V
|
1 × |
Capacitor, aluminium electrolytic, 10 µF, 25V
|
2 × |
Capacitor, aluminium electrolytic, 47 µF, 25V
|
1 × |
Capacitor, ceramic, 1 nF, 100V
|
3 × |
Capacitor, metallized polyester foil, 10 nF, (0.01 µF)
|
1 × |
D-sub soldering cups, 15 pin male
|
1 × |
D-sub soldering cups, 9 pin female
|
1 × |
DIL socket, 16-pin, 7.62mm
|
1 × |
DIL socket, 28-pin, 7.62mm
|
1 × |
Enclosure, plastic (1591 FL), 120x65x40mm, flange
|
1 × |
Fuse 5x20 mm, 200 mA, fast-acting
|
1 × |
Fuse holder, open, PCB, 5x20mm
|
1 × |
Fuse holder, open, PCB, Protective cover
|
1 × |
Heatsink, 27.3K/W, 19mm, attachable, TO220
|
1 × |
Humidity sensor, HIH 4000, 0 - 100 %, +4 to +5.8 V
|
1 × |
LED 5mm clear, Yellow, 2.0V, 20mA, 250mcd, 6°
|
1 × |
LED 5mm coloured clear, Green, 2.1V, 20mA, 30mcd, 10°
|
2 × |
LED holder 5mm, RTC51, black plastic
|
64 cm2 |
PCB, stripboard, 100x160mm, 160cm2
|
1 × |
Power jack, panel, 2.1mm, plastic housing
|
2 × |
Resistor, carbon film, 0.25W, 330 Ω, 5%
|
2 × |
Resistor, carbon film, 0.25W, 4.7 kΩ, 5%
|
1 × |
RS232 interface, MAX232CPE, dual
|
25 × |
Straight pin header, female, Single row, 2.54mm
|
25 × |
Straight pin header, male, Single row, 2.54mm
|
1 × |
Temperature sensor LM35DZ, 0 to +100 °C, +-0,6 °C
|
1 × |
Transistor, NPN, 100 mA, 45V, 0.5W, BC547B
|
1 × |
Voltage regulator +5V, 2 A, L78S05CV
|