The purpose of this project is to allow parents to remotely check both the temperature of their baby and the humidity of the diaper. I used wearable Lilypad technology sewn into a baby blanket.
This sensor detects humidity in any piece of cloth. The circuit I used amplifies the currents that goes between two small metal pieces (see figure 3 – 6 humidity sensor)
It used one of the analog ports of the Arduino to read the values (from 0 to 1024) .The sensitivity can be adjusted in the code. I used 10 as being my threshold value: whenever the sensor reads a higher value than 10 it will alert that it is time to change the diaper.
The circuit is composed by one transistor and two resistors. In order to be able to sew the electronics into the blanket, I made a PCB “lilypad style” (see figure 1-2 – humidity sensor), using the method described on Paulo Coelho’s web site.
For reading temperature, I used a small temperature sensor that was designed to be wearable (description here). It detects physical touch based on body heat and ambient conditions. This sensor outputs 0.5V at 0 C, 0.75V at 25 C, and 10mV per degree C. I found out that it has a slow response; it takes more than 2 minutes to read the temperature of the skin. (see figure 2-5 – temperature sensor)
I chose to use the Bluetooth Mate (description here) which was designed specifically to be used with the LilyPad Arduino.(see figure 3- 4 Bluetooth)
I used Processing to build the computer interface.
The temperature value is always displayed on the monitor.
For humidity, there are two different screens: when the diaper is dry it displays screen 1; when it is wet it displays screen 2.
Screen 1 – Dry Diaper Screen 2 – Wet Diaper