Development of a CTE Project: An IoT Electronic Thermometer, Part 2

In my previous article , I discussed how I'm developing an Internet of Things curriculum for my CTE (Career Technical Education) high school students in electronics technology by using the Cypress Semiconductor BLE Pioneer Kit with a PSoC board. The emerging technology curriculum's objective is to teach basic design engineering and new product creation methods by way of building an IoT wireless sensor instrument. The new product creation engineering steps I plan to use are summarized, as follows:

  • Receive customer product requirements
  • Develop product specifications (hardware/software)
  • Build proof of concept (PoC) prototype
  • Test PoC prototype
  • Demo PoC prototype to customer
  • Revise PoC prototype for manufacturing production
  • Product launch

I discussed the importance of receiving customer product requirements and the first developmental gate to designing an IoT device in my previous article. Also, I summarized the process of developing product specifications for hardware and software design elements, illustrating it by using PSoC Creator's hierarchical diagram and the health thermometer's product description document features/functions flowchart.

With such product specifications and customer requirements on hand, my students will be able to build PoC prototypes for functional testing. Off-the-shelf electronic kits are great for building the PoC prototypes because of rapid development in wiring circuits using solderless breadboards. Since the IoT product is based on temperature sensing, the Radio Shack Electronic SensorLab was the best choice for building the PSoC BLE electronic circuit interface.

Testing the Health Thermometer PoC Prototype

The next phase of the IoT project is to test the PoC prototype of the health thermometer. A small room heater will be used to change the thermistor's resistance so the CySmart app's profile of the health thermometer can display the temperatures on a Bluetooth-enabled mobile device.

This testing of the PoC prototype provides a technical training discussion on the electrical operation of thermistors and voltage divider circuits. The theory behind the electrical operation of thermistors and voltage dividers can be expressed as a simple equation:

Where:

Vthermistor is the output voltage of the electronic sensor

Rthermistor is the resistance of the thermistor

Rtotal is the summation of the thermistor and 10 kilo-ohm series resistance

V3.3V is the supply voltage (3.3 V) powering the voltage divider circuit.

A DC voltmeter can be attached across the thermistor to monitor the voltage as temperature changes affect its resistance.

The Project's STEM Connection

Besides teaching basic electrical circuit theory, the health thermometer is an excellent hands-on tool for STEM projects, as well. The science behind the health thermometer can be explored by way of temperature conversions. I plan on adding a STEM element to the IoT curriculum by having the students convert Celsius to Fahrenheit measurements using the equation:

As Celsius data is being transmitted from the health thermometer's electronic sensor to a smartphone or tablet, the temperature values can be recorded into a lab notebook. Basic math skills in using order of operation can be taught and reinforced with the health thermometer, as well. The final conversion values from the health thermometer can be entered into an Excel spreadsheet.

Two columns will be used for entering Celsius data

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