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Non-contact cloud-based temperature sensor with speech To help track the health of the employees in our department, I have created this non-contact temperature sensor at the entry point. All you need to do is place your forehead close to it (within 2-5cm), and it measures your body temperature and plays back audio to indicate whether it is normal or high. It also uploads the data to a cloud server (www.thingspeak.com) for later analysis. It uses an HC-SR04 ultrasonic sensor to measure the distance to the person. Once that distance is close enough, it measures the temperature, plays back an audio file depending on the reading, then uploads the data to the internet. If it detects that someone is nearby, but not close enough (between 5cm and 78 Silicon Chip 15cm), it plays back an audio file asking them to approach closer. The ESP32 has two digital-to-analog (DAC) outputs at pins 9 & 10 (IO25/26). Audio playback in this case is from pin 9. One of two 8kHz PCM (pulse-code modulated) audio files is played back depending on whether the temperature measurement is below or above 37°C. A special Arduino library is used for this capability (XT_DAC_Audio from xtronical.com). A small 5V audio amplifier using the PAM8403 IC is used to deliver this sound to a 3W 8W loudspeaker. The ESP32’s WiFi capability is used to upload the temperature data to the cloud server at www.thingspeak.com The Arduino sketch to load onto Australia’s electronics magazine the ESP32 is available for download from siliconchip.com.au/Shop/6/6052 You will need to open a free account at www.thingspeak.com and modify the API key in the software to match the one you are supplied with before it will upload data. It supports multiple WiFi networks with separate SSIDs and passwords, so that whichever one is found will be used to transfer data to the cloud. You will need to modify the SSID and Password section of the sketch to contain your network details. The circuit uses two ESP32 modules; one is dedicated to handling the audio playback while the other monitors the temperature and distance sensors and drives the display. siliconchip.com.au The voice-handling module is programmed to play back one of the two sound files when pin 28 or 29 is brought high, and these pins have pulldown resistors to prevent audio playback at power-up or when the other micro is reset. The main ESP32 connects to the ILI9163 colour TFT display via an SPI serial bus, the HC-SR04 ultrasonic ranger via a two-pin digital interface and the MLX90614 IR temperature sensor via an I2C serial bus. As well as playing back the appropriate sound file, the unit also lights the red or green LED (red = high temperature, green = normal temperature), and it sounds the connected piezo buzzer if the temperature is high. Both the ESP32s may be powered from one 5V DC power supply. The audio data I have created is in the files “fever.h” and “ok.h”, while the file that is played when someone is not close enough for measurement is in “wel.h” (short for “welcome”). To change this, first record your desired audio to 8kHz, 16-bit WAV files. You then need to change these files to HEX format. There are many online sound converter sites such as www. fromtexttospeech.com that can do this. You then need to convert the HEX data to C code by using the software HxD from www.mh-nexus.de which produces a simple text file that you can use to replace “fever.h”, “ok.h” or “wel.h”. You can see the data recorded on my cloud server at www.thingspeak. com/channels/1371171 Besides showing the temperature readout on the screen, it also shows a letter code in the lower-left corner. C = Connected to WiFi, U = Data Uploaded, D = Distance measurement. Any form of ESP32, ESP32S or ESP32 S2 module will work for this project. Bera Somnath, Vindhyanagar, India. ($100) Editor’s note: while normal body temperature is generally considered to be 36.5-37°C, it is possible to measure above 37°C without being ill. Some people are simply hotter than others, and exertion and other factors can affect your core temperature to a certain extent. That time of year is nearly here... CHRISTMAS Spice up your festive season with eight LED decorations! Tiny LED Xmas Tree 54 x 41mm PCB SC5181 – $2.50 Tiny LED Cap 55 x 57mm PCB SC5687 – $3.00 Tiny LED Stocking 41 x 83mm PCB SC5688 – $3.00 Tiny LED Reindeer 91 x 98mm PCB SC5689 – $3.00 Tiny LED Bauble 52.5 x 45.5mm SC5690 – $3.00 Tiny LED Sleigh 80 x 92mm PCB SC5691 – $3.00 Tiny LED Star 57 x 54mm PCB SC5692 – $3.00 Tiny LED Cane 84 x 60mm PCB SC5693 – $3.00 We also sell a kit containing all required components for just $14 per board ➟ SC5579 siliconchip.com.au Australia’s electronics magazine December 2021  79