This incredibly simple thermometer plugs on any free serial port. Does not make use of any programmable components as microcontrollers. It gives temperature readings accurate to 0.5°C with no calibration. It's very cheap (DS18S20 cost in Dallas-Maxim less than 3$)
The DS1820 thermometer from Dallas Semiconductors DS1820 is suitable for this kind of applications. Multidrop capability simplifies connection using only two wires. Features:
unique 64-bit lasered ROM code in each sensor
measuring range -55...+125 °C
accuracy ± 0.5 °C between 0...70 °C
resolution 0.5 °C, also higher resolution possible
uses 1-Wire(tm) interface (DATA, GND)
powered from DATA line
i have used this IC with a 68HC11 microprocessor. very simple, requires only 1 resistor as an external part (it can operate in "parasitic" mode in which the resistor is not even needed!!) one signal line, power & ground.
my advice, use an oscilliscope to verify that you are meeting the *minimum* timing requirements as listed in the datasheet of the DS18B20.
i have used this IC with a 68HC11 microprocessor. very simple, requires only 1 resistor as an external part (it can operate in "parasitic" mode in which the resistor is not even needed!!) one signal line, power & ground.
my advice, use an oscilliscope to verify that you are meeting the *minimum* timing requirements as listed in the datasheet of the DS18B20.
Interesting, what pin did you use on the HC11?
How long could the wire between the DS1820 and the HC11 be?
Do you have any schematic to show?
What about multiple devices on that bus?
Possibly any code?
i used pin PA7. this is a generic I/O pin.
i do not know the maximum length of the wire. perhaps the datasheet can tell you. the wire i used was about 4 feet long.
the schematic is too simple. power, ground, one resistor.
you can find a picture of schematic and code (written for a PIC 16F877) here: