09. Remote Temperature and Humidity Sensor for new parents

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.

Figure 1 – Electronics in the banket

Figure 2 – Sensors

Figure 3 – Sensors in baby clothes

I used two sensors: a temperature sensor and a humidity sensor. The temperature sensor will be placed in the baby’s clothes, and the humidity sensor in the diaper.

1.Humidity Sensor
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.

2.Temperature Sensor
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)

4.Computer Interface
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



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4 Responses to 09. Remote Temperature and Humidity Sensor for new parents

  1. Norma Holly Eslick says:

    You seem to have the technology necessary to create something many of us Type 1 diabetics desperately need: a wristband that can sense when the skin’s temperature is dropping and starting to sweat. When blood sugar drops to unsafe levels the skin gets cool and clammy (sweaty). This is especially dangerous at when you’re asleep because it can get low enough to cause seizures, coma, or even death. I’ve had a number of seizures and had EMS come to give me dextrose injections when my son/husband couldn’t wake me up to give me juice. There used to be a wristband that worked quite well, except that it gave a lot of false positives. I LOVED it and the false positives were a small price to pay in my opinion. When it stopped working I tried to get another one and found out they were no longer available. Not sure why. Please give this some serious consideration.

    Thank you,
    Norma Eslick

  2. dominic rooijackers says:

    Hello Daniel

    Do you have a layout of the humidity PCB ?
    I’d like to make a similar device, and would like to base it on yours

    Thank you in advance
    Dominic Rooijackers

  3. Emmanuel says:

    Hello Daniel,

    is it possible to show me how your complete circuit looks like? i’d like to try building it myself

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