Sensor Explorations

Jon Lai / Katie Suskin

Since our last post, we have decided to focus on the water drinking situation. We want to create a water bottle that can remind the average, busy person to drink water while they are sitting at work or at school. We explored several possibilities for sensors that we could use to measure the water level in a bottle. Initially, we wanted to build some sort of water flow sensor that would detect the amount of water that passed through the spout of the bottle. We were inspired by one of Teague’s explorations measuring water used from a tap. However, this seemed too complicated to apply to our water bottle scenario. Our other options were:

• An optical sensor that would work with water’s refractivity to measure the level visually
• Contact liquid sensor (less elegant, water eventually corrodes metal)
• Weight sensor to measure changes in amount of water (maybe not very accurate)
• Capacitive level sensing: strips of foil on either side of bottle measuring height of water

After some research, we discovered an instructable in which the author created a capacitive level sensor for liquids in a bottle and also hooked up a small LCD display to show the levels visually. We looked over his code and discovered that arduino.cc has a preexisting library that can turn two or more pins into a capacitive sensor. Instead of an LCD display, we plan on working with LEDs to alert the user when it is time for them to drink water again. Below is a pseudo code diagram of how we envision our system to work.

We experimented in class with the capacitive sensor code from the arduino website and had some exciting results. The original code just printed the different capacitance levels detected, but we added an LED that would turn on when it sensed certain levels of capacitance. We merely had to wave our hand over our sensor for the LED to turn on.

Our next task will be to measure water levels in a bottle with capacitive sensing.