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())

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# 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

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##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.