Web thermostat with Arduino

By on May 4, 2011
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The Circuit
We start our description of the hardware on this card from the temperature sensor: it is a DS18B20 equipped with a logic that can express in binary format, two bytes, the temperature measured by its sensor element and the data on the surveys are made available through a serial communication channel called one-wire.
The Ethernet module is a WIZNET network adapter that can be interfaced via the SPI bus (Serial Peripheral Interface) 4-wire.
The module is a WIZ811MJ ethernet (IEEE 802.3/802.3) and W5100-based chip with full magnetic filters ethernet connector and 2 LEDs for status signaling. The module communicates with the microcontroller by SPI. It works with 3.3 Vcc and the 3V3 are provided by Arduino.
The connector J3 is that counts the largest number of connections: it comes from the control signal of the transistor T1, the controller of the relay RL1 (in parallel with the coil there is the LED LD2, signaling,  the excitement of the relay). Through J3 the Arduino reads status of buttons P1 and P2 and the input IN, all with pull-up resistor. The yellow LED LD1 is used to give the state mode or assist the setting of operation modes made with the P1 button. This allows you to choose between modes of operation of the system: sensor, manual or thermostat. Pressing once set the system in the sensor mode (automatic) and that this operation is indicated by a flashing dell’LD1, two pressures set the sistem in manual mode (command from web page), which is indicated by two flashes Led. Finally, three pressures set the system in thermostat mode (slave input IN), and this is communicated by three consecutive flashes dell’LD1. Pressing the button P1 returns the sistem in the first mode.
As for P2, currently not used and is reserved for future developments.

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R1: 4,7 kohm
R2: 10 kohm
R3: 470 ohm
R4: 4,7 kohm
R5: 4,7 kohm
R6: 4,7 kohm
R7: 4,7 kohm
R8: 4,7 kohm
U2: DS18B20
P1: Microswitch
P2: Microswitch
LD1: led 3 mm yellow
LD2: led 3 mm red
T1: BC547
RL1: Relé 5V
D1: 1N4007
- Screw connector 2 via
- Screw connector 3 via
- Strip male 6 via(2 pz.)
- Strip male 8 via (2 pz.)
- Strip female 10 via (4 pz.)

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About Boris Landoni

Boris Landoni is the technical manager of Open-Electronics.org. Skilled in the GSM field, embraces the Open Source philosophy and its projects are available to the community.


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