The Water Dog
Caitlyn Millen
Balmacewen Intermediate
An adult dog is about 60% water. While a dog can lose all of its fat and half of its protein and survive, if it loses only 10% of its body water, it is in serious trouble. Dogs are particularly vulnerable to dehydration. Because they have sweat glands only on their nose and foot pads, they have to cool themselves by panting, losing in the process lots of fluids. On a hot day, the average dog can become dehydrated in only a few hours if fresh water is not present.
For most dog owners this isn't a problem – a bowl of clean water, regularly topped up, does the trick. But not for 12-year-old Caitlyn Millen, a student at Balmacewen Intermediate in Dunedin. Caitlyn's dog, Mishka, refuses to drink out of a bowl and insists on drinking from the bath tap. This is annoying for the humans of the household – somebody has to turn the tap on and off – and potentially dangerous for Mishka, who sometimes has to wait for Caitlyn or her parents to come home before she can drink.
There had to be some way around this problem Caitlyn reasoned. What was required, she figured, was something that would provide fresh running water, with very little wastage; something that required very little maintenance; and something Mishka could use by herself.
Her solution? The Water Dog. In simple terms it's a water container with a pump that feeds a spout that Mishka can lap out of whenever she feel like it. Where the design is particularly ingenious is the way Caitlyn found to allow the water to flow only on demand and to keep the container topped-up. A clever system of sensors and feedback loops ensures wastage is eliminated. When Mishka approaches the unit, an infrared movement sensor activates, via a relay, the pump which feeds the spout. A float switch – similar to the switch in a toilet cistern – controls inflow from the hose via a solenoid valve. When the animal moves away, the sensor shuts down the pump and the water stops flowing.
Water and electricity can be a dangerous combination. So to reduce danger and make the unit portable, Caitlyn opted for battery power. To make the unit sustainable, Caitlyn used a solar panel to charge the battery with a charge controller to prevent overcharging.
Caitlyn says the best part of the project was designing the fountain. "I enjoyed coming up with all the different ideas for what was needed, then looking at the positives and negatives of each idea and deciding what ideas to keep in the design."
"My biggest challenge was figuring out the electronic work. It was confusing at the start and it took a while to get all the wires and components set up properly."
Caitlyn did her best to make her design as simple and maintenance-free as possible, but the unit still requires regular cleaning. It's no good putting clean water in a dirty container.
Caitlyn placed first in her group at the 2011 BrightSparks finals held in Christchurch in November.
The best thing about the project? "I really enjoyed working with my Dad and I was really pleased when the fountain worked and Mishka drank from it." One improvement to the design Caitlyn has thought of is to install a water temperature control device, as pets prefer cool water in the summer and room temperature water in the winter.
And her next invention? "My favourite sport is synchronised swimming. If I could invent anything in the world it would be a comfortable swimming cap."
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