IR Temperature Sensor

This Instructable demonstrates how to create a mobile infrared temperature sensor and have the temperature readings be displayed on a Bluetooth capable device, such as an Android phone. In this particular case, we had the IR thermometer take the tympanic (inner ear) temperature once every hour for a 24 hour period and log this data on the phone. In order for the device to be mobile, it was powered by a 9V battery regulated to 5 and 3.3V.

How it works:

1. The IR thermometer will sense the temperature.
2. The temperature will be sent as an analog signal to the Arduino Uno.
3. The Arduino will convert the analog signal into a digital signal.
4. The digital signal will then be sent to the BlueSMiRF.
5. The BlueBMiRFwill transmit the temperature to the Bluetooth capable Android phone.

Step 1: Gather Materials

• 1 x Arduino Uno
• 1 x BlueSMiRF Bluetooth Modem
• 1 x Infrared (IR) thermometer
• 1 x 0.1 uFarad capacitor
• 2 x 4.7 kOhm resistors
• 1 x PCB
• Insulated wire
• Soldering iron and solder
• 1x Bluetooth capable device (ex. Android phone)
• 1 x 9V battery

Step 2: Draw Circuit Design

Before soldering, it is a good idea to draw out the circuit design on a photocopy of a PCB. This will help prevent errors when it comes to placement of components and unnecessary soldering.

We made a large photocopy of the PCB and drew out placement of the BlueSMiRF, IR thermometer, capacitors, and resistors. Connections to the Arduino were also noted. When it came time to solder, having a diagram made it much more efficient.

Step 3: Solder

Once the circuit has been drawn onto the copy of the PCB and you have looked all circuit connections over, it is time to solder.

We soldered the BlueSMiRF on first, then the IR thermometer, capacitor, resistors, and the wires to connect all components, including the Arduino, to the circuit. No wires were soldered directly onto the Arduino.

If you've never soldered before, here is a helpful video:

Step 4: Coding the Arduino

We adapted different code found online in order to make the device do what we wanted. We mainly combined two files. The first file allowed the temperature from the IR thermometer to be displayed in the command window. The second file allowed whatever was typed into the command line to be printed to a Bluetooth device. Combining these files allowed us to display the temperature from the IR thermometer directly onto the Bluetooth device.

The Arduino code that we used is attached.

Step 5: Collecting Data

The final step is to collect the data. The device was worn for 24 hours while temperature measurements were taken once each hour. These measurements were then logged and plotted.