2023 Build

Motivations

My son will graduate high school and begin college in 2023 and that upcoming change led to this redesign. I wanted a design that is more robust, simpler, and more versatile than the original. I need it to be less prone to breakage, easier to adapt to things like new Wi-Fi networks, easier for me to support remotely, etc. I changed some feature (dropped and added some) to help achieve those goals.

Here is an overview:

• A robustness gain was to stop splitting the RPi and the GPIO devices between the box lid and the box base. The multiple times per day bending of the wires between the two is a reliability weak point.
• Versatility and simplicity were enhanced by using a larger box with everything inside the base, which meant that I could build the entire basalsure system on a plastic platform that can be easily moved to a different box, if one is damaged or style preferences change.
• The 433 MHz alarms that we have used for years have been wonderful for reliably alarming across my home without the need for Wi-Fi or commercial power, but with my son off at college, alerting across a house is not required. Moreover, in 2022 I added USB speaker support that provides both voice prompts and loud audible alarms right from the box itself. I also added Pushover.net support in 2022 and it, Twilio, and SMTP to SMS have been 100% reliable, as long as the basalsure box has connectivity to the Internet.
• When I added USB speaker support in 2022, I learned that driving USB speakers is right on the edge of (and sometimes beyond) the USB output power capability of the USB port on the RPi Zero W. That, combined with my desire to have standard USB-A ports and a wired LAN connection, had me decide to use a RPi 3 B+ in this new build. Not only can the RPi 3 B+ drive small USB speakers without issue, but having a LAN port could be very helpful in situation where Wi-Fi is not reliable or I need to provide tech support to my son's basalsure device.
• Having several regular USB-A ports on the RPi 3 B+ also made it practical for the Wi-Fi settings to be "hot configured" from a configuration file placed on a USB flash drive and simply inserted. Hot configuring Wi-Fi setting from a USB flash drive can be very benficial on a headless single board computer like this. As part of this basalsure design update, I wrote software to do exactly that and it is hosted here: https://github.com/hightowe/wpa-hotconfig

Materials

Hardware

• A book- or treasure-box, size 2.7"D x 7.5"W x 10.6"H, akin to these: 1, 2, 3
• Raspberry Pi 3 B+: https://www.amazon.com/dp/B07P4LSDYV
• Real Time Clock (RTC) module: https://www.amazon.com/dp/B08X4H3NBR
• Optocouplers / Photoelectric Sensors: https://www.amazon.com/dp/B08977QFK5
• USB speaker: https://www.amazon.com/gp/product/B075M7FHM1 (I tried several and preferred this one).
• 3VDC Buzzer: https://www.amazon.com/dp/B09V3H38JP/
• SD Cards:
  • https://www.amazon.com/dp/B08HHWY422 (cheaper and I use for testing)
  • https://www.amazon.com/gp/product/B07P14QHB7/ (more expensive but reliable)

Consumables

• ABS plastic sheet, 1/16" thick (many options available): https://www.amazon.com/gp/product/B0049MWXM8
• I mounted my optocouplers on a small strip of wood that is about 8mm thick. Likely best to grab something similar from a local arts and crafts store, or consider using a thicker piece of ABS plastic.
• Dupont wires: https://www.amazon.com/dp/B01EV70C78/
• Solder Seal Heat Shrink Butt Connectors: https://www.amazon.com/gp/product/B07JHJ8G5X
• Heat Shrink Tubing: https://www.amazon.com/gp/product/B01MFA3OFA
• Double-sided Velco: https://www.amazon.com/dp/B000078CUB
• Sticky-backed Velcro: https://www.amazon.com/dp/B0013AIAQ2

• Screws: https://www.amazon.com/dp/B09LV7945S

• Zip ties - https://www.amazon.com/dp/B08TVLYB3Q

Tools

• I used a paper trimmer similar to this one to cut the 1/16" ABS perfectly: https://www.amazon.com/dp/B09M66Y3J6
• A small heat gun or a cigarrette lighter.
• A screwdriver or two.

Wiring Instructions

The wiring instructions for the 2023 build are simpler than for the 2018 Build, but it may be helpful to spend a few minuted reading the [2018 Build - Wiring Instructions] to help ground you in the concepts, as I only provide the high-level wiring diagrams here.

In the wiring diagram below, the colors of the wires don't matter, of course. It is conventional to use red and black for +VDC and -VDC or ground, and so I followed that. Then I chose yellow, green, and blue for the three input signal colors. The 3VDC buzzer that I used came pre-wired with red and black and so its red wire plugs directly into the GPIO terminal pin that turns it on, and its black wire goes to ground.

Let's start with a simple diagram of the layout of RPi GPIO pins:

Image from: https://www.raspberrypi.com/documentation/computers/raspberry-pi.html

Now I show the wiring (and wire colors) that I used in this build and the purpose of each wire and pin:

Note that I purposely greyed out all GPIO pins that are not used, which is the majority of them.

The Real Time Clock (RTC) Module

In this build, I used a small RTC module that just plugs directly onto pins 1-9, which was more convenient than the larger RTC module that I have used in the past that requires a separate mounting point and wiring. Both RTC modules use the same chip and the software configuration is identical, and it is documented within Adding a "Real Time Clock" (RTC) module.

The USB Speaker

The USB speaker can be plugged into any of the RPi USB ports. I chose the bottom outside one to leave the top ports open (for a USB flash drive) and to have space between the USB speaker wire and the Ethernet port.

Note that the USB output power on the RPi devices, and particularly on the Zero W devices, cannot drive high current draw speakers. I tried several small USB speakers and the one that I recommend above was the winner, by far.

Power

I choose to power all of my RPis using the micro-USB port designed for that purpose. It is important to be sure that you provide adequate voltage (5.1VDC) and current (2.5A for RPi 3) that means using a high quality power supply with impecable specifications. A Raspberry branded one is not required, but may be a good idea for novices who want to avoid having low power problems.