Sudden Infant Death Syndrome (SIDS) is the unexplained death of an infant less than a year old, and is most common between birth and 4 months. In 1994, the American Academy of Pediatrics launched the "Back to Sleep Campaign," urging parents to place their babies on their back instead of their belly or side to go to sleep, as either of the latter options can restrict breathing. In the 10 years following the launch of the campaign, reports of SIDS decreased by about 50%.
The "Back to Sleeper" encourages safe sleeping for babies in the at-risk age range. Through embedded sensors on the back, the sleeper can sense when the baby is not on their back, initializing a beep to sound.
An Arduino Gemma was used for the microcontroller due to its small size. It reads the two back sensors (connected by stainless steel thread and conductive paint traces) as inputs and triggers a piezo buzzer as output.
To create the sensors, I painted conductive paint onto Bemis overlay tape that's bonded with the fabric. A layer of soft cotton batting separates the two conductive paint layers, allowing them to come in contact with each other when pressure is applied by the baby laying on his/her back. The sensors were originally intended to be used as digital pushbuttons, but can also be used as analog inputs. The two sensors share a common ground.
The conductive paint dried stiff when applied directly onto fabric, and was not conducive to the stretching nature of the knit as the paint would separate. To remedy this, I tested mixing the conductive paint with varying amounts of fabric paint to soften it; however, I found that ratios between conductive and fabric paint that created a soft application were no longer conductive. So, I applied the conductive paint on top of overlay tape instead. This method also protects the traces from getting wet if the baby wets their diaper.
Soldering the piezo buzzer and resistor to the Gemma