A simple digital thermometer with your own hands.

Apply this thermometer with a remote sensor connected to the computer via the COM port, possibly starting from maintaining the climatic conditions of various storages, incubators, aquariums, controlling the temperature regimes of high-end audio equipment and ending with observations of weather conditions with preservation of data for further processing; In any places where the range of measured temperatures and the error of the thermometer meet.

Several sensors can be connected to one 2 (3) wire lines, and thus, at a minimum cost, control the temperature at several points.

To assemble an electronic thermometer, the following components will be needed:
1) The DALLAS DS1820 thermal sensor is the most important part of the entire circuit, the sensors can be mounted in parallel. According to the description, each sensor has its own 64 bit ID, which makes it possible to simultaneously use 100 sensors on the bus, 300 meters long, it was not possible to check, but two sensors on a 5-meter-long tire work successfully.
2) Zener diodes at 3.9V, 6.2V, 5.6V, the lowest power - they are more compact.
3) Schottky diode, 1N5818 was used in the amount of 2 pieces.
4) Diode 1N4148 - 1pc.
5) Resistor 1.5KΩ, 0.25W - 1pc.
6) Condenser 10μF, 16V - 1 piece.
7) 9-pin COM-port connector, type - Mom.
8) Connector housing.

The components must be assembled according to the following scheme:

DS18S20 (DS1820) - Digital thermometer with a single-wire interface in the standard MicroLAN, the range of measured temperatures from -55 ° C to + 125 ° C. The absolute error of the conversion is less than 0.5 ° C in the controlled temperature range from -10 ° C to + 85 ° C (for DS1820 - 0.5 ° C in the range from 0 ° C to + 70 ° C). The resulting temperature value is read from the device as a nine-digit word. The maximum time of full conversion is ~ 750ms (for DS1820 - ~ 500ms). The node of the 1-Wire interface of the device is organized in such a way that there is a theoretical possibility of addressing an unlimited number of similar devices on one single-wire line. The thermometer has an individual 64-bit registration number (group code 010N) and provides the ability to work without an external power source, only due to parasitic power supply of a single-wire line. The power supply of the device through a separate external terminal is made by voltage from 3,0V to 5,5V. The thermometer is located in the transistor case TO-92.

Mounting can be carried out directly on the connector, with some dexterity, enough tight fitting can be accommodated in the connector housing, which is undoubtedly convenient and practical.

The thermometer is ready, and especially well, everything works without any calibration of the sensors. It only remains to connect the sensor to the COM port of the computer and install the temperature measurement program .

The Temp program. Keeper is designed to monitor and monitor the temperature and humidity of various objects or environments in which the sensors will be placed.

You can visually observe on the computer for the changes that occur, as well as control the finding of the specified parameters in the norm, warning you with a sound signal , if necessary.

Main features of the program:
- Automatic detection of connected sensors by command
- Individual alarm settings for each sensor
- Two modes of interrogation, allowing to work both with sensors using parasitic power, and with sensors with external power supply
- Display of measured parameters on the graph for more convenient evaluation of their changes
- Output of the selected audio signal for each object
- Calculation of the average room temperature in multipoint control
- Display of measured parameters in the system tray for one of the sensors
- The program is designed to work under Windows 95, 98, 2000, NT4 (requires Servis Pack 3 or higher).

The administration of the site is not responsible for damaging the computer due to improper assembly of the sensor.