Hello and welcome to Mr Ericksen’s home on the web. This isn’t so much a portfolio of my work as it is a place for me to archive my projects and processes while providing a convenient way for me to share them with others who may be interested in using them.

If you’re just browsing around, Technotes are tech-related projects I’ve worked on as an IT Director and EdSys Admin, Travel Hacks is a collection of things I’ve found helpful during since moving abroad in 2006, and Pro Tips are just some short tips for making daily life a little less stressful.


Air Quality Monitoring on a Corporate Scale

South Korea doesn’t have the worst air in the world, but it’s also no Chippewa Falls, Wisconsin. Recognizing that very bad air days are a threat to the health of our students and staff, our school developed a systematic plan to monitor the air we breath and to filter bad air when necessary. As part of this effort, several staff, faculty and students worked together to build a network of air quality monitoring stations around campus to collect timely data, share current data with stakeholders, and record data long-term for research and future planning. These devices were surprisingly accurate except during times of high humidity when the SDS011’s readings become unreliable. Ultimately, the school’s brass decided to go with a commercially available system for it’s needs. But I have preserved the following explanation of how we built the devices and installed the software to disseminate current data and stored data for future use.

We built a variation of the Sensor.Community’s project. This uses the Plantar SDS011 PM2.5/PM10 particulate matter detector, BME280 temperature/humidity/pressure monitor, the WEMOS D1 Mini ESP8266 development board and a super small breadboard to bring it all together. Note that these items can also be commonly found virtually anywhere that sells microelectronics components and they’re inexpensive. The SDS011 sensor is around $17, the others are a few dollars each.

Setup is fairly straightforward. We attach headers to the Wemos D1 Mini and the BME280. Then we connect the 5V pin of the D1 to the 5V pin of the SDS011,

Wiring Connections:

Wemos D1 MiniSDS011BME280
Sensor wiring connections

Once everything is connected, we’ll want to flash the Wemos D1 Mini’s code. Visit the Sensor.Community’s download page to retrieve the appropriate version. Connect the Wemos D1 to your computer, and run the flashing program to set it up. If your computer does not recognize the Wemos D1, you may need to install the driver to see it. The driver page is mostly in Chinese, so you will need to look closely to discern which version is needed for your OS.

Once flashed, you’ll need to reboot the device by disconnecting from your computer and then reconnecting – either to your computer or another micro-USB power source.

The first time it restarts, it won’t know how to connect to your local WiFi, so it creates its own WiFi network. On your computer, look for a new SSID that begins with Feinstaubsensor-ID or airRohr-ID followed by a chip ID such as 13597771. Connect to that SSID and note the chip ID as it will be needed later. Once connected, point your browser to and you should see the device setup page. From here, you can select your preferred language, enter your local WiFi network name and password, and identify the sensors connected to the device. Be sure to click the “Zurük zur Starseite” button to save the settings and restart the device.

There are are a couple ways to check your sensor readings. You can access your device directly on your local network if you can identify and visit its local ip address. Alternatively, you can create an account at https://sensor.community to conveniently access your device data online. You’ll need the Chip ID you wrote down earlier to find your sensors. But once your account is set up, you’ll be easily able to bookmark your device to see your local air quality, temperature and humidity conditions.


Bulk Editing Google Docs with a Script

We used Google Docs for elementary progress reports. A spreadsheet and Autocrat let me create all the files and even drop them into folders by homeroom class. But that’s not what this is about.

After teachers started entering grades, the principal noticed that the grading key was missing some information. The easy fix would have been to recreate the docs and have the teachers start over. But this would have created extra work for teachers on one of their least enjoyable tasks.

A quick Google search led to a script that would allow me to edit the documents en masse. Not surprisingly, the starter script came to me via Amit at https://labnol.org. It takes the folder path containing the docs to be edited, the “search” text and the “replace” text. Then it goes through all the docs in the folder, makes a backup and then does the search/replace in each doc.

Amit’s script is effective but limited to a basic find/replace in the body text of Google Docs in one folder.  I expanded it to allow formatting text in addition to find/replace in Google Doc headers, bodies, and footers across multiple folders. You can find my script here.

Just as I expanded Amit’s script, when you’re ready to expand mine, visit the Class Text section of Google Apps Script tutorials for more options.


Roughneck Totes as Checked Baggage

Rubbermaid’s 25 gallon Roughneck Tote is the best container to use as checked baggage when transporting a lot of stuff via intercontinental flights. The length + width + height dimensions are the maximum allowed by airlines, maximizing the volume per piece of baggage, they stack nicely on airport carts and the handles make loading and unloading convenient. I have used this method since 2008, moving back and forth from the U.S. to Kuwait, Nigeria and South Korea, taking a couple dozen of these totes on several dozen flights. I’ve never had a problem and never lost a tote or lid.

They’re available at most Ace Hardware stores. On Amazon.com, the shipping charges are prohibitive. But if you visit my favorite hometown Blain’s Farm and Fleet, you can get 4 of them shipped just about anywhere in the US for around $20 each. While you’re there, throw in your 14″ zip ties, colored duct tape, packing tape, and Sharpie.

The only challenge is closing them up to remain sealed during travel. But, there is an easy way of handling this. I use a 5/16″ drill bit (8mm) to put 12 holes strategically placed around the lid which accept plastic zip-ties or 16 gauge solid-core copper wire to keep the tote sealed.

It’s important to put the holes in the right place so that if you use several totes, any lid will be able to be used on any tote with the lid and tote holes lining up perfectly. Check out my video for the details:


Get notification when Autocrat fails to run

We have several leave request forms that get processed by the Autocrat Add-on. Inevitably, Autocrat seems to get stuck and fails to run. This is an issue for us when staff are submitting forms expecting that they will be acted upon while our crack team of support staffers remain unaware that the requests have been submitted.

Whenever Autocrat runs, it adds a note logging successful completion into the cell in the last row, last column of this spreadsheet. If this cell is blank, Autocrat has failed to execute. So, I came up with this little script. It checks the form responses spreadsheet’s last row and column every 6 hours (adjustable). If that cell is empty, indicating an Autocrat failure, an email is sent to me which looks like this:

To use this yourself, click here for the script. Copy the code and paste it into a new script in your form’s spreadsheet (Tools > Script Editor). Then set a trigger for the script to run at your preferred time interval.

Raspberry Pi Sound Effects Player

Long story short? I made an RPi sound clip player using a tft touchscreen, pygame, and movie quotes found on YouTube. It starts with a small, 3.5″ touchscreen whose drivers are installed using the instructions here. For your convenience, they are replicated below.

Just enter these lines into Terminal to get the screen set up.

sudo rm -rf LCD-show
git clone https://github.com/goodtft/LCD-show.git
chmod -R 755 LCD-show
cd LCD-show/
sudo ./LCD35-show

This should get the screen running properly. If you have issues with axes being reversed on the screen (like you touch the right side and the cursor shows up on the left) the page linked above has some suggestions. If those don’t help, check out Teng Fone’s post on Medium.

OK, now (hopefully) the screen is working and we can work on the code. I used code from Garth Vander Houwen’s Pi tft menu project as a starting point, added some audio files, and came up with a project that presently shows this screen on my Raspberry Pi:

Sounds Player Screen

You might guess some (or all) of the audio files I used. If not, you can download them from here.

The Python script to get it all running is below (or access it here). Connect the audio output to your speakers or headphones and click away. Examining the code should make it relatively easy to modify it to change the sounds, number of options, etc.

import sys, pygame, time, subprocess, os
from pygame.locals import *
from pygame import mixer
from subprocess import *

os.environ["SDL_FBDEV"] = "/dev/fb1"
os.environ["SDL_MOUSEDEV"] = "/dev/input/touchscreen"
os.environ["SDL_MOUSEDRV"] = "TSLIB"

# Initialize pygame modules individually (to avoid ALSA errors) and hide mouse

# define function for printing text in a specific place with a specific width and height with a specific colour and border
def make_button(text, xpo, ypo, height, width, colour):
    label=font.render(str(text), 1, (colour))
    pygame.draw.rect(screen, blue, (xpo-10,ypo-10,width,height),3)

# define function for printing text in a specific place with a specific colour
def make_label(text, xpo, ypo, fontsize, colour):
    label=font.render(str(text), 1, (colour))

# define function that checks for touch location
def on_touch():
    # get the position that was touched
    touch_pos = (pygame.mouse.get_pos() [0], pygame.mouse.get_pos() [1])
    #  x_min                 x_max   y_min                y_max
    # button 1 event
    if 30 <= touch_pos[0] <= 240 and 30 <= touch_pos[1] <=85:
    # button 2 event
    if 260 <= touch_pos[0] <= 470 and 30 <= touch_pos[1] <=85:
    # button 3 event
    if 30 <= touch_pos[0] <= 240 and 105 <= touch_pos[1] <=160:
    # button 4 event
    if 260 <= touch_pos[0] <= 470 and 105 <= touch_pos[1] <=160:
    # button 5 event
    if 30 <= touch_pos[0] <= 240 and 180 <= touch_pos[1] <=235:
    # button 6 event
    if 260 <= touch_pos[0] <= 470 and 180 <= touch_pos[1] <=235:
    # button 7 event
    if 30 <= touch_pos[0] <= 240 and 255 <= touch_pos[1] <=310:
    # button 8 event
    if 260 <= touch_pos[0] <= 470 and 255 <= touch_pos[1] <=310:

# Define each button press action
def button(number):
    print("You pressed button", number)

    if number == 1:
        #time.sleep(0.2) #do something interesting here

    if number == 2:
        #time.sleep(5) #do something interesting here

    if number == 3:
        #time.sleep(5) #do something interesting here

    if number == 4:
        #time.sleep(5) #do something interesting here

    if number == 5:
        #time.sleep(5) #do something interesting here

    if number == 6:
        #time.sleep(5) #do something interesting here

    if number == 7:
        time.sleep(2) #do something interesting here

    if number == 8:
        time.sleep(5) #do something interesting here

#colors     R    G    B
white   = (255, 255, 255)
red     = (255,   0,   0)
green   = (  0, 255,   0)
blue    = (  0,   0, 255)
black   = (  0,   0,   0)
cyan    = ( 50, 255, 255)
magenta = (255,   0, 255)
yellow  = (255, 255,   0)
orange  = (255, 127,   0)

# Set up the base menu you can customize your menu with the colors above

#set size of the screen
size = width, height = 480, 320
screen = pygame.display.set_mode(size)

# Background Color

# Outer Border
pygame.draw.rect(screen, blue, (0,0,480,320),10)

# Buttons and labels
# First Row
make_button("I'll be back", 30, 30, 55, 210, blue)
make_button("Wicked Smart", 260, 30, 55, 210, blue)
# Second Row
make_button("That'll Do", 30, 105, 55, 210, blue)
make_button("Killing me", 260, 105, 55, 210, blue)
# Third Row
make_button("Failure", 30, 180, 55, 210, blue)
make_button("Good Night", 260, 180, 55, 210, blue)
# Fourth Row
make_button("Don't do nothin", 30, 255, 55, 210, blue)
make_button("Exit", 260, 255, 55, 210, blue)

#While loop to manage touch screen inputs
while 1:
    for event in pygame.event.get():
        if event.type == pygame.MOUSEBUTTONDOWN:
            pos = (pygame.mouse.get_pos() [0], pygame.mouse.get_pos() [1])

        #ensure there is always a safe way to end the program if the touch screen fails
        if event.type == KEYDOWN:
            if event.key == K_ESCAPE:
    ## Reduce CPU utilisation

Ubuntu and WiFi on 2011 MacBook Pro

We had tried a few years ago to get some ancient MacBooks up and running with various Linux distros. But our particular model had challenging WiFi hardware which made it impractical.

I recently took another shot at reinvigorating our Early 2011 MacBook Pros with Ubuntu and found that a few terminal commands would get things working. I used Andy Bleaden’s steps from this AskUbuntu answer. I’ve pasted the steps below to ensure I always have ready access to it.

From Andy Bleaden:
I always recommend removing and reinstalling the broadcom drivers using your terminal

In a terminal type the following command

sudo apt-get purge bcmwl-kernel-source


sudo apt-get install bcmwl-kernel-source

This will then rebuild your driver.

You can either restart your pc or if this is a pain type the following commands in the terminal which will ‘switch on’ your wireless

sudo modprobe -r b43 ssb wl


sudo modprobe wl 

PowerSchool Contract Tracing with DDE

Suppose a student tests positive for COVID-19. Here’s how we quickly identify potentially exposed classmates. There’s a sample spreadsheet here that you can use. Just make a copy, follow the steps below and paste the export into cell A1 of the PS_DataDump tab. If that link breaks, you can download an Excel version here.

  1. In DDE, select the CC Table
  2. Search for current TermID and StudentID
  3. Switch over to Sections Table
  4. Search for Sections in current term
  5. Match Selection on CC table
  6. Switch to CC Table
  7. Select all enrollments from current term
  8. Match Selection with Sections Table
  9. Export Records with the following records:


Password Protecting Student Reports

In our ever increasing efforts to protect student confidentiality and personal information, we password protect student report cards and test results when emailing them to parents. This helps protect the information in the unlikely event that an email gets sent to the incorrect address.

To do this, we generate the reports from PowerSchool or Google Docs, typically in a Firstname Lastname grade # Progress Report.pdf format. These are put into a folder (in this case, the folder is ES_T3_PDFs) there is also a filedata.csv file that has each file’s password in the first column, the original filename in column 8, and the new filename in column 9.

The python script below then runs, opens each report, creates a new file object, password protects it, and writes it to a new folder (Secure_ES_T3_PDFs).

import PyPDF2
import csv
import sys
#Open csv with password,filename,newfilename
c = open('filedata.csv', 'r')
# Create a reader object to store the data in filedata.csv
reader = csv.reader(c, delimiter=',')
# Process each row of data
count = 0
for row in reader:
    # The password located in the first column
    password = str(row[0])
    # The current (original) filename in "firstname lastname grade # Progress Report - Student_Number" format
    currFileName = row[7]
    # New filename is the same as original but without the Student_Number 
    newFileName = row[8]
    # Skip the header row
    if (password != "Password"): # Skip the first row with "Password" in first column
        # print row # every 10th row - just to monitor progress
        if (count % 10 == 0):
        # Open non-encrypted file
        pdfFile = open("PasswordProtect/ES_T3_PDFs/"+currFileName, 'rb')
        #coverLetter = open("PasswordProtect/coverLetter.pdf", 'rb')
        # Create reader and writer objects
        pdfReader = PyPDF2.PdfFileReader(pdfFile)
        #pdfReader02 = PyPDF2.PdfFileReader(coverLetter)
        pdfWriter = PyPDF2.PdfFileWriter()
        # The next 2 lines put the welcome letter at the beginning of the new file
        #print("Inserting Cover Letter")
        #for pageNum in range(pdfReader02.numPages):
        #    pdfWriter.addPage(pdfReader02.getPage(pageNum))
        # Add all pages to writer for each page in input file, add it to the output file
        for pageNum in range(pdfReader.numPages):
        # Encrypt with password
        # Write it to an output file
        resultPdf = open("PasswordProtect/Secure_ES_T3_PDFs/"+newFileName, 'wb')
    count += 1

Pro Tips

Open Google Docs/Sheets, etc. without owner knowing you’ve done so.

If you want to open a shared Google Drive file without the owner seeing that you’re in the doc, you can just make a copy of it rather than opening the actual doc. To do this, copy the link of the shared file, paste it into your browser’s address bar, and change the “/edit?…” part at the end to “/copy”.

Replace everything after the last slash with “/copy”

Google will prompt you with a blue “Make a Copy” button. Click it, and you’ve got your own copy of the file that you can peruse without the owner knowing you’ve accessed it.

Preventing Problems while Permanently Storing Grades in PowerSchool

Peculiar enrollment situations can lead to issues when permanently storing grades at the end of a term. For instance, if a student changes from one section of a course to another during a term, one grade could get stored for each section if the “Exclude enrollments” dates are not selected wisely.

"Exclude Enrollments" options

While we keep a file of “Special Cases” to review at the end of each term, but there are often such cases that sneak by us. To catch them, I track down all enrollment anomalies before storing grades.

To do this, I use DDE (…/admin/tech/dde/):


  • Select the CC table
  • TermID >= current year term (2900, 3000, 3001, etc.)
  • SchoolID = 200 for MS or 300 for HS (in our case)
  • DateEnrolled >= “A couple weeks after the start of the term”
  • Export to a spreadsheet
  • Sort by course name and delete non-courses: clubs, sports, A-Block, etc.
  • Sort by DateEnrolled and look for any peculiar dates later in the term
  • Decide appropriate cutoff date for “enrolled… after”
  • Note any enrollments that may be improperly included or rejected for later followup
  • Repeat above steps changing DateEnrolled to DateLeft and find an appropriate time for “dropped… before”

I typically check “Exclude … dropped before…” about a week before the end of the current term. Checking for outlier dates can help identify individual students and enrollments that may need attention.

Receive Raspberry Pi’s ip address on boot

I do a lot of Raspberry Pi projects – often creating them in one place and using them in another. While it is easy enough to use SSH, VNC or HTML to access a device, if it’s being moved from one network to another, it can be challenging to know its ip address. Sure, you may be able to log into a local router and look it up, but I thought it would be easier if I just had the RPi email me with its current ip address.

Thankfully, Cody Giles created a tutorial on elinux.com outlining how to do this. His Python script runs on the RPi on startup, finds its ip address(es) and then emails this information to a predetermined address. I’ve replicated his project (and code) below to ensure I’ll have access to it in the future.

In order to allow a Python script to send email through a Gmail account, you may need to enable an “App Password” for your sending account.

Step #1: Create the Python Script

Copy the following and paste it into a text editor. You must change the ‘to’ address, as well as the ‘gmail_user’ and ‘gmail_password’ for the sending account in the lines below the pound sign lines about 25 lines from the top. Save this file as a python script in the home directory named startup_email.py.

__author__ = 'Cody Giles'
__license__ = "Creative Commons Attribution-ShareAlike 3.0 Unported License"
__version__ = "1.0"
__maintainer__ = "Cody Giles"
__status__ = "Production"

import subprocess
import smtplib
from email.mime.text import MIMEText
import datetime

def connect_type(word_list):
    """ This function takes a list of words, then, depeding which key word, returns the corresponding
    internet connection type as a string. ie) 'ethernet'.
    if 'wlan0' in word_list or 'wlan1' in word_list:
        con_type = 'wifi'
    elif 'eth0' in word_list:
        con_type = 'ethernet'
        con_type = 'current'

    return con_type

## Change the 'to' address,'gmail_user', and 'gmail_password' below.  ##
to = 'username@email.com' # Email to send to.
gmail_user = 'username@gmail.com' # Email to send from. (MUST BE GMAIL)
gmail_password = 'gmailpassword' # Gmail password.
smtpserver = smtplib.SMTP('smtp.gmail.com', 587) # Server to use.

smtpserver.ehlo()  # Says 'hello' to the server
smtpserver.starttls()  # Start TLS encryption
smtpserver.login(gmail_user, gmail_password)  # Log in to server
today = datetime.date.today()  # Get current time/date

arg='ip route list'  # Linux command to retrieve ip addresses.
# Runs 'arg' in a 'hidden terminal'.
data = p.communicate()  # Get data from 'p terminal'.

# Split IP text block into three, and divide the two containing IPs into words.
ip_lines = data[0].splitlines()
split_line_a = ip_lines[1].split()
split_line_b = ip_lines[2].split()

# con_type variables for the message text. ex) 'ethernet', 'wifi', etc.
ip_type_a = connect_type(split_line_a)
ip_type_b = connect_type(split_line_b)

"""Because the text 'src' is always followed by an ip address,
we can use the 'index' function to find 'src' and add one to
get the index position of our ip.
ipaddr_a = split_line_a[split_line_a.index('src')+1]
ipaddr_b = split_line_b[split_line_b.index('src')+1]

# Creates a sentence for each ip address.
my_ip_a = 'Your %s ip is %s' % (ip_type_a, ipaddr_a)
my_ip_b = 'Your %s ip is %s' % (ip_type_b, ipaddr_b)

# Creates the text, subject, 'from', and 'to' of the message.
msg = MIMEText(my_ip_a + "\n" + my_ip_b)
msg['Subject'] = 'IPs For RaspberryPi on %s' % today.strftime('%b %d %Y')
msg['From'] = gmail_user
msg['To'] = to
# Sends the message
smtpserver.sendmail(gmail_user, [to], msg.as_string())
# Closes the smtp server.

Step #2: Make the script executable.

Using Terminal, navigate to the home directory and make the script executable.

cd ~
sudo chmod +x startup_email.py

Setp #3: Run the Script on Startup.

We’ll add a line to boot.rc to run the script whenever the RPi boots.

sudo nano /boot/boot.rc

Add the following lines to boot.rc

python /home/pi/Code/startup_email.py

Now, reboot the Pi and in about a minute, you should receive an email with your device’s IP address.

Forcing DNS on macOS in Recovery Mode

When resetting a 2020 MacBook Air, we ran into an issue where the device just wouldn’t connect to Apple’s servers. It felt like a DNS issue, but I couldn’t find a way to see or set DNS values. After some searching, I came across this Stack Overflow post with the solution. As that site was sold to a tech investment firm in June, 2021 (promising not to change a thing), I thought it best to preserve it here.

Here it is:

Usually DNS-server setup in the shell is done with sudo networksetup ... – a tool not available in the Base OS X System of the Recovery Mode.

You should still be able to change the DNS server with scutil in Terminal.app:

  1. Open Terminal.app in the menubar > Utilities
  2. Enter scutil --dns to get your current DNS config
  3. Enter scutil to reach interactive mode
  4. Enter list to get a list of all keys in the data store
  5. If you have several interfaces (you’ve found several State:/Network/Service/SERVICE_ID/IPv4 entries) determine the one connected to the Internet (based on e.g. your router and its internal network IP settings) – example:get State:/Network/Service/EB40E2FC-8248-48F2-8567-257D940A31EB/IPv4 d.show Example output:<dictionary> { Addresses : <array> { 0 : } ConfigMethod : Manual SubnetMasks : <array> { 0 : } } If your router has the IP-address this should be the proper interface. If your router has e.g. the IP address the interface found above would be the wrong one and you have to search for an interface with an IP in the range
  6. Enter get State:/Network/Service/EB40E2FC-8248-48F2-8567-257D940A31EB/DNS use the service ID of the interface connected to the Internet you have found previously (here EB40E2FC-8248-48F2-8567-257D940A31EB)Entering d.show should show something like:<dictionary> { SearchDomains : <array> { 0 : some.domain } ServerAddresses : <array> { 0 : } } Depending on the DHCP setup of your router the SearchDomains entry and array may be missing.
  7. Enter d.add ServerAddresses * – add one or more DNS-server (here Google’s and quad9’s
  8. Enter set State:/Network/Service/EB40E2FC-8248-48F2-8567-257D940A31EB/DNS
  9. Enter d.show to check the modified dict entry. It should show something like:<dictionary> { SearchDomains : <array> { 0 : some.domain } ServerAddresses : <array> { 0 : 1 : } }
  10. Enter quit to leave the interactive mode of scutil and return to the shell.
  11. Enter scutil --dns or dig to verify your new DNS config.