This
practical temperature controller controls the temperature of any device
according to its requirement for any industrial application. It also displays
the temperature on an LCD displays in the range of –55°C to +125°C. At the
heart of the circuit is the microcontroller from 8051 family which controls all
its functions.
An IC
DS1621 is used as temperature sensor. The DS1621 Digital Thermometer and
Thermostat provides 9-bit temperature readings, which indicate the temperature
of the device. User-defined temperature settings are stored in a nonvolatile
memory EEPROM through 8051 series microcontroller.
Maximum
and minimum temperature settings are entered to the MC through a set of
switches which are stored in the EEPROM -24C02.Maximum and minimum setting are
meant for allowing any hysteresis necessary. Set button is used first and then
the temperature setting by INC and then the enter button.
Similarly
for the DEC button. A relay is driven from the MC through a transistor driver.
The contact of the relay is used for the load, shown as a lamp in the circuit.
For high power heater load a contactor may be used, the coil of which is
operated by the relay contacts in place of the lamp as shown.
Standard
power supply of 12 volt DC and 5 volt through a regulator are made from a step
down transformer along with a bridge rectifier and filter capacitor.
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