The Sixth Sense | a not so technical guide to sensors
Ever since the advent of the IoT age , we know for a fact that even our smart-devices are capable of talking and communication to one another in their own unique way (i.e. using some sort of a standard communication protocol). The reason why they communicate could be anything from receiving to sending instructions or to be receiving or sending SENSOR data.
What are Sensors?
Sensor’s aren’t anything new to us. They have been around us for decades, often ignored as they have seemingly become a part of our day-to-day lives. Let’s take an example of that one thing that everyone of us has in our pockets, the humble smartphone. It’s fascinating to know how many sensors we are carrying around with us on a daily basis. The camera that you love taking pictures with is nothing but a CMOS Image Sensor. The thing that automatically adjusts your screen brightness in peak daylight is nothing but an ALS(Ambient Light Sensor). Something that’s even as crude as let’s say a mercury thermometer is also a type of a sensor. The list goes on but what I want us to take away from this is that a SENSOR is nothing but a device or a system that enables us to measure or detect a physical quantity.
Now one might ask this question, how do sensors work and how does the host controller know what the sensed data is? Well that’s the most fascinating part of this whole topic. It’s this beautiful symphony of Electronics and Mechanics , with some help from their parents, Physics and Mathematics and sometimes their aunt chemistry but for our own sanity ,let’s just stick to the electromechanical part.
How Sensors work
Let’s take an example of two kids on a seesaw. There were three friends Walter, Jesse and Gus. All of them wanted to play on the seesaw but we all know it can only accommodate two people at any given time. When Walter and Jesse were playing , Walter realized that he had to push up every time the seesaw came down on his end, thus he figured out that Jesse was lighter than him. But when he started to play with Gus, he saw that he had to put much less effort as the seesaw was more or less balanced. Thus he figured Gus weighed more than Jesse and almost equal to himself. This is how in a very archaic way, Walter figured out or at least made an assumption of how much Jesse and Gus weighed. This is not that different from how an actual PRESSURE SENSOR works. In this case Walter acted as the host device and the seesaw was the Sensor.
Now a real pressure sensor is bit more complicated than that , but in a simple way we can look at it as a translator who translates a mechanical , optical or magnetic phenomenon into an electrical signal that the processing unit can interpret and map the aforementioned phenomena into the digital domain.
But the question still remains. How does it do it?
R L C (Robots Love Computers)
Well not really. Though RLC is an apt acronym for Robots Love Computers (which I’m sure they do) , it’s not what it actually stands for. RLC stands for the three pillars of any electrical circuit i.e. RESISTANCE, CAPACITANCE and INDUCTANCE.
So now that that’s out of the way let’s restart.
R L C (Resistance Capacitance Inductance)
As we learnt these are the three pillars of any electrical circuit , any changes made to these would in-turn change the I-V Characteristics of the circuit that can then be detected by the host processor to calculate the certain physical phenomena.
I-V stands for Current and Voltage , two terms I’m pretty sure everyone has heard like a few hundreds if not thousands of times in our lives. From our physics classes in school we also have a brief idea of what they are. Basically circuits are built for the very reason to control these two in such a way that we can give us the desired result. Now going back to our humble pressure sensor let’s look at how it works.
Since we are oversimplifying things with random examples. Let’s do that one more time.
We have all seen a faucet at home. It’s simple, we open the tap and water starts flowing at a rate proportional to how much the tap has been opened. Now as you close the tap , the water slows down and as you open it more it speeds up. This is mimicking exactly what a pressure sensor might do if a load is applied on it. the distance between the faucet and your sink (the distance the water needs to travel ) is your voltage. The rate of flow of water is your current and finally the tap is your resistance.
Similarly a constant current flows through the sensor which is kept track of by the host controller. When pressure is applied the resistance of the sensor changes hence changing the amount of current flowing through it. The difference of this new value from the set previous value is directly proportional to the amount of pressure applied.
But hey! what’s piezo resistance. In a very simple way some metals have the characteristic to change their resistivity depending upon how much they are bent (Some crazy molecular physics which frankly has it’s own book).
Congratulations! now you know how a sensor works (at least somewhat ) and crucially how it interacts with a data processing device and how all of this incorporates itself in the whole IoT ecosystem.
Conclusions
Now that I have hopefully been able to explain the inner workings of one of the most commonly used sensors , it should be fascinating to know for a fact that we are surrounded by these things . Imagining a world without digital cameras or RFID authentication is close to impossible. The amount of data that these sensors are collecting on a day-to- day is staggering and need for more efficient Data processing systems are the need of the out. With the introduction of IoT and Smart devices, sensors are playing an integral role in our society and this demand for them is only rising as we march towards a smarter future.
Finally, I would like to conclude with one of my favorite Richard Feynman quote’s.
Hopefully with this I have been able to help some of the non-technical folks out there understand the idea of sensors and how they work and I wish this has been somewhat informative and fun way to learn about technology.
With that I have one last question for you. The next time you walk up to a shopping mall entrance and the door opens on itself. will you simply walk by or will you stand for second and appreciate the hidden ingenuity in it?