Reading and decoding Temperature Data from Arduino¶

(This is Part 2 of the Measuring Temperature Lab ).¶

For this lab you will need pyserial. This can be installed thru Anaconda the same way we did Basemap. Try either of the following options for installation.

# Use an R kernel from jupyterlab
install.packages("serial")

Some Cliff Notes on Dataframes¶

This exercise uses dataframes. Base R generates data frames by default. At the time of creation, it is possible to specify the name and data type of each column in the dataframe.

# time is stored as a string, while resitance and temperature are numeric

dd <- data.frame(time = character(), resistance = numeric(), Temp = numeric())

In [7]:

# Load the libraries
# install.packages("serial")
library("serial")
library("lubridate")

Open the serial connection using the serialConnection() command.

You will need to find the exact port name on your computer. Hint: This can be found in the Arduino Tools menu under "port".

In [8]:

# Assign the serial object that you will write to and read from
#S <- serialConnection(port = "cu.usbmodem1101",mode = "9600,n,8,1")
#open(S)

Warning message in open.serialConnection(S):
“cu.usbmodem1101 is already open and will be reconfigured!”

'Reconfigure!'

Port cu.usbmodem1101 ( 9600,n,8,1 ) is open.
Buffer usage (in/out): 9/0

Warning message in print.serialConnection(S):
“Try summary() for more information!”

Initialize the three variables you will be using to store (time, resistance, temperature).

In [3]:

# Initialize  dataframe to capture time, resistence, and Temp, as shown in datetime notes.

Set the coefficients for the Steinhart-Hart equation

In [4]:

##1/T = A + B*Ln(R) + C(Ln(R))^3
A = 0.001125308852122
B = 0.000234711863267
C = 0.000000085663516

In [6]:

# Set a while loop or for loop.  You can make it go indefinitely until you kill the loop with Kernel -> Interrupt.
#lp = 0
#stop <- 'go'

# Use a for or while loop.  You can make it go indefinitely until you kill the loop with Kernel -> Interrupt.
#while (stop == 'go'){


    # Use the write.serialConnection() command to send a data request to the Arduino.

    # Sys.sleep(2) # Add an N-second pause to allow the buffer to be filled.

    # Read a line from the Serial data object stored in 'S'. Note, readline() line returns a byte array. 
    # You can convert to a string using decode('utf-8').  You may also want to investigate the .strip() function 
    # that will remove unwanted characters. 
    a <- read.serialConnection(S)

    
    # Parse the string.  In R, it will be easiest to just send the numeric value of resistance without any
    # other text characters.
    
    # Use an 'if statement' if necessary and append the new resistance value to the array 'R' that was initialized 
    # above.
    # Compute Temperature using A, B, C coefficients and the resistance value.
    # Convert Temp in deg Kelvin to deg C.
    # Record the date and time using the datetime package.  
    # Append the datetime, resistance, and temperature as a new row in your Pandas Dataframe.
    if (a != "") {
      tryCatch(
    {
            # Get the time stamp for now

            # Convert the resistance reading from the serial connnection into a numeric value

            # Compute temperature from resistance and the Steinhar-Hart coefficients.
    
            
            # Append a new row with current time and iterator value with rbind

    },
    error = function(e) {
      print("incomplete string")
    }
      )
    }



    # Save the data to a csv using the pandas function df.to_csv() where df is the name of your dataframe.
    # You can use a conditional statement to do this every N'th time, e.g. every 100th time.
  
    write.csv(dd, "my_data.csv")
}

close(S)

Completing your data collection¶

Close the connection to the Serial data object. (THIS IS REALLY IMPORTANT)!!!
Make a plot of Temperature vs. time.

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Make a plot of Temperature vs. datetime. Save that plot using plt.savefig()

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What to turn in:¶

See instructions in Thermistor Lab Part 2.