ATmega8535 + LM35DZ + LCD + Keys + Relay

Do not misinterpret the title above, it is not a mathematical expression with variables ATMEGA8535, LM35DZ, etc.. The title above is a monitoring system and microcontroller based temperature controller with temperature sensors LM35DZ ATMEGA8535 equipped with a digital viewer in the form of 16 × 2 character LCD. The system also has several buttons for setting operational parameters. As a control output relay is used which has a terminal NO, NC, and COMMON.
                                                Here is a photo system I'm referring to ...

The system can detect a temperature between 000-100 degrees Celsius. The actual temperature of the PV (Process Value) displayed continuously on the LCD with an accuracy behind the decimal comma. In addition to actual temperatures, the program also displays the temperature of the target SV (Setting Value) and the condition of the relay status (ON / OFF).
To make setting a target temperature of the SV (Setting Value), it is used operational buttons. In addition to the target temperature, the system also has several parameters that can set the MODE, HYS, and CAL.
MODE can be set to the value HEATING or COOLING. This parameter indicates the application of the controller. If MODE = HEATING, it serves as a heater controller that controls the load of the heating element. In this mode, if the actual temperature (PV) less than the target temperature (SV), then the relay will be ON. Working system controller as the heater can be illustrated by the If-Then statement as follows:

    If (SV-PV> = HYS) Then RELAY = ON

    Else If (PV-SV> = HYS) Then RELAY = OFF
If MODE = COOLING, then the controller that controls the cooling function as a pump or fan loads. In this mode, the controller works in contrast with the Heating mode.
HYS (Hysteresis) is a plus-minus is used as a benchmark by the controller to turn off or turn on the relay. Such as SV = 70 and HYS = 2, then the relay will be ON during PV <= (SV +2), and the relay will be OFF when PV> (SV +2). Furthermore, the relay will be ON again when PV <(SV +2).
CAL (Calibration) is a constant value of temperature display proofreaders. Such a temperature controller displayed 28 degrees, while the instruments that we make the benchmark show the temperature of 29 degrees. Then the controller temperature display can be customized by adding the value 1 in the CAL parameter. So the temperature controller is shown PV + CAL.
Similarly, a glimpse of ATMEGA8535-based temperature control system equipped with an LCD display, keypad operation, the output relay.