Need help with writing a program to control a temperature sensor

Using Arduino Project Guidance
1

Help with writing a program to control a temperature sensor

Hello,
I am new to Arduino and would like some help writing a program to control a temperature sensor with two push button switches (normally open).

A temperature sensor will be connected to an analogue input pin A0. A heater will be controlled by PWM using pin 11. A relay to completely remove power from the heater circuit will be controlled by pin 1. A 16 X 2 LCD display will be used to display the set-point temperature , the actual temperature, the on/off mode and the duty cycle of the heater output. Start and Stop pushbuttons connected to pins 2 and 3 will be used to start and stop the process. These two pins are to initiate a hardware interrupt where the system is either started or stopped within the interrupt routine.

Another two inputs are used to increase or decrease the set-point temperature while the program is running. The set-point is incremented or decremented by 1 for each operation of these inputs. The lower set-point value is to be limited to 25 Degrees C and the upper limit is to be 45 Degrees C.
The temperature sensor has an output of 10mV / Degrees C. Where 0 Degrees C will have an input of 0V and 100 Degrees C will have an input of 1V. These voltages relate to a binary number range of 0 to 204. You will have to manipulate these values to numbers that represent the actual temperature being measured.

The duty cycle of the output controlling the temperature should be at 100% when the actual temperature is 5 Degrees C or more less than the set-point. As the temperature approaches the set-point temperature, the duty cycle is to reduce by 20% for each degree closer to the set-point.

e.g. At 4 Degrees C less than the set-point, the Duty Cycle = 80%
At 3 Degrees C less than the set-point, the Duty Cycle = 60%
At 2 Degrees C less than the set-point, the Duty Cycle = 40%
At 1 Degrees C less than the set-point, the Duty Cycle = 20%

When the temperature equals the set-point, the Duty Cycle = 0%

When the process is started, a relay supplies power to the heater and will energize and stay on until
the stop button is pressed. Use a separate function for each of the following tasks:

  1. Reading the analogue input and manipulating the value to a number that represents the actual temperature.
  2. Calculating the heater duty cycle.
  3. Incrementing and decrementing the set-point value.
  4. Displaying data on the LCD.
  5. Starting and Stopping the process (interrupt routine).

Connections:
Temperature sensor pin A0
Start pushbutton pin 2
Stop pushbutton pin 3
PWM (mosfet) pin 11
Relay pin 0
LCD pins 5 to 10

Thanks for your insights!
Paul

2

Can you post a link to the temperature sensor ? You are connecting to an analog input but have said it delivers a 'binary' representation of the voltage.
What LCD are you using ? 6 pins is too many for an I2C connected LCD and 6 seems too small for non-I2C models.

You have been given specific pins to use in this exercise, or are you free to choose ?

Edit:
I've just read it again.

The temperature sensor has an output of 10mV / Degrees C. Where 0 Degrees C will have an input of 0V and 100 Degrees C will have an input of 1V. These voltages relate to a binary number range of 0 to 204. You will have to manipulate these values to numbers that represent the actual temperature being measured.

The information about the binary number range is irrelevant and is probably designed to confuse the student. Looks like you have some interesting homework to do :slight_smile: . This may help you get started (but it is not for the Arduino) Interfacing LM35 Temperature Sensor with PIC Microcontroller.