The schematic for the project is given in the Schematics Section below.
A typical "wall-wart" power-supply is used (a surplus laptop charger in this case) in conjunction with a voltage regulator (LM7805) to provide the regulated 5V required by the PIC microcontroller and the other circuit components. The D18S20 sensors are on the same supply as for the PIC microcontroller in this case.
The schematic shows the basic minimum circuit to demonstrate the operation of the D18S20 sensors, in this case, controlled/interfaced to a PIC16F876A microcontroller which also provides data output to PC via RS232 connection.
The LM7805 provides the 5V circuit voltage (stepping down from the 12V input from a "wall-wart" power-supply). The crystal X1 and associated capacitors C1 and C2 provide the oscillator for the PIC16F876A microcontroller. Incircuit serial programming (ICSP) of the PIC16F876A microcontroller is provided via connector J1 with switch SW1, resistor R1 and diode D2 providing voltage protecting during loading code into the PIC microcontroller.
Control signals to/from the PIC16F876A microcontroller are sent from a suitable port on the microcontroller (port B in this case) in order to control the D18S20 sensors and retrieve data.
The D18S20 sensor provides the temperature data digitally and notionally does not require calibration (datasheet stated accuracy ±0.5oC).
Calibration checking of temperature data from the D18S20 however can be performed using water baths (or similar) at known temperature (e.g. via mercury glass-bulb thermometer).
The D18S20 provides simple digital control and a serial interface for retrieval of data using a "one-wire" protocol. The "one-wire" refers to the single data line, however, the sensor still obviously requires V+ and ground, so three wires are required to connect the sensor.
Specific information about developing the necessary firmware/C code library for the DS18S20 temperature sensor with PIC microcontroller is documented seperately. This page documents the incorporation of DS18S20 digital thermometers into a practical functioning device.