Temperature and humidity sensor (RS232)

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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

  • PD0 Rx
  • PD1 Tx

D-sub 15-pin

  1. 13.8V
  2. 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

Git-alt-brands.svg
Bascom-AVR source is available in a git repository:
https://github.com/thomasjsn/AVR-Temp-humidity-sensor-RS232

Gallery

  • Temp humid sensor-20150919 234649.jpeg
  • Temp humid sensor-20150919 234701.jpeg
  • Temp humid sensor-20150919 234706.jpeg
  • Temp humid sensor-20150919 234716.jpeg
  • Temp humid sensor-20150919 234729.jpeg
  • Temp humid sensor-20150919 234743.jpeg
  • Temp humid sensor-20150919 234757.jpeg
  • Temp humid sensor-20150919 234831.jpeg
  • Temp humid sensor-20150919 234849.jpeg
  • Temp humid sensor-20150919 234901.jpeg
  • Temp humid sensor-20150919 234910.jpeg
  • Temp humid sensor-20150919 234924.jpeg
  • Temp humid sensor-20150919 234936.jpeg
  • Temp humid sensor-20150919 234957.jpeg
  • Temp humid sensor-20150919 235005.jpeg

Schematic diagram

AVR temperature humidity sensor circuit.png

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
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