Sometimes we get suprise rain showers in the middle of the hot Texas summer. While I marveled at the ground soaking up the drizzle the last time it rained, I took the opportunity to check on my irrigation system - one of the many home automation systems that seems to live on an island.
And sure enough, after only three years of operation, the rain sensor needed a new battery.
It’s not really a big deal until you actually get started: I had to take out the ladder, set it up, climb the ladder, take the sensor down, remove the batteries, buy new batteries, hopefully remember to recycle the old ones, put it all back together, get on the ladder again and put the sensor back in place.
Wouldn't it be much better if the sensor could live forever (or at least 10 years like most major appliances in a household)? And wouldn’t it be better if it wouldn't stick out from the side of my house like a landing pod for bonsai aliens? And while we are compiling a wish list, wouldn’t it be nice if the rain sensor could do a little more - like regulating how much to water depending on the amount of rain, sun and temperature?
So, I am down from my ladder and have opened the rain sensor, only to find that the battery compartment takes up more than half of the overall device. Which is so much more of a surprise when you look at the mechanical "rain sensor" that is quite substantial in size. And some quick online research shows that my sensor is not the exception.
It looks like we need to reduce the power this thing consumes for two reasons. First, to increase its operating life and, secondly, to reduce the size and make it look better. The solar powered keyboard I have been using for two years now is an example of a product that meets those criteria. The lack of a battery compartment makes it much slimmer than any other office keyboard I have seen. And did I mention that it has worked flawlessly for all that time? No changing batteries required, not even in my dimly lit office.
I did not want to break the keyboard open, so I ended up here. I found that a small rechargeable battery stores all of that precious light energy when I am not typing. Since the keyboard worked right out of the dark box, the battery must have been pre-charged. This really is a battery plus harvesting approach. The battery always has enough charge to operate the sensor. When light is available, it charges until the battery is full or the light goes off. The sensor can operate whenever it is needed with the battery capacity plus the energy harvested enough to last the life of the sensor.
The sensor is back up on the side of the house and waiting for the next rain. All the tools are stored away again and I am wondering what the next rain sensor should look like – perhaps it will combine a very small rechargeable battery with a solar panel, work for 10 years and even enable additional functionality.
My little rain sensor is just one example of the innovation happening around sensors today. In parallel, more and more of these sensors will move off their island to form local networks, which in turn will connect to the internet. A key component to this trend is for the sensors and electronics to be smaller and have fewer mechanical components. Both of which are right at the heart of what Texas Instruments does.
Below is a TI sensor tag with a humidity sensor built in. What sensor would you want to use if it would operate autonomously, blend in and provide more functionality?
