[From the last episode: Amazon just had a glitch that sent a random conversation to a random contact.]

This week we start our look at sensorsA device that can measure something about its environment. Examples are movement, light, color, moisture, pressure, and many more. and actuatorsA way of controlling some device electronically. It might turn the device on or off or change a setting or property or do any other thing that the device is capable of.. There’s lots of technology to talk about in order to make sense out of this.

Before we get into that, why are we talking about sensors and actuators together? After all, they’re two of the four essential IoT elements. Why aren’t we dealing with one and then the other?

The answer is that, even though they’re philosophically opposites (one sees what’s happening, the other makes something happen), they’re built in very similar ways. And, sometimes, they’re even together in the same unit.

What’s Old is New

Of course, sensors and actuators are nothing new; they’ve been around for decades – ever since industrialization. What’s new is the scale: now they’re so tiny that you have multiple sensors in your phone. (You mostly don’t have much actuation in your phone, although gyroscopesA sensor that detects when it changes direction. are an example of a sensor that requires actuation to make it work. We’ll look at that in detail sometime in the future.)

An example of an old sensor/actuator pair is the trusty cruise control in your new or old car. You may not think of it this way, but it works by sensing your speed. If the speed drifts off of the target speed you set, then it actuates the throttle either to speed up or to coast down. (The system could involve another actuator that would apply brakes, but that’s not how it works. That would probably have lots more issues than simply monkeying with the throttle.)

Now, imagine taking that system down to the micro- or nano-scale! (We’ll talk about what those scales mean more specifically in a few weeks). You could have a siliconAn element (number 14 in the periodic table) that can be a semiconductor, making it the material of preference for circuits and micro-mechanical devices. chip that does it for you – if you could shrink the speed sensor and throttle down to the size where it would fit on a chip.

Chipping Away

And that’s what we’re going to talk about: how to do these things not the old-fashioned way, but the modern way — by putting these devices on silicon chips, just like a computer chipAn electronic device made on a piece of silicon. These days, it could also involve a mechanical chip, but, to the outside world, everything looks electronic. The chip is usually in some kind of package; that package might contain multiple chips. "Integrated circuit," and "IC" mean the same thing, but refer only to electronic chips, not mechanical chips..

And the way these are built, well, you’re not going to believe some of the clever, creative things that have been done. Sensor-makers (and actuator-makers) have taken the ways that electronics are built and adapted them to build mechanical systemsThis is a very generic term for any collection of components that, all together, can do something. Systems can be built from subsystems. Examples are your cell phone; your computer; the radio in your car; anything that seems like a "whole.".

As you’ve probably seen, mechanical linkages can be extremely complex, ungainly, and failure-prone. The modern way of doing things is to deal with the mechanical real world as little as is necessary and convert as soon as possible to electrical. And the same way for actuators: keep the signal electrical as much as possible, and then convert to mechanical at the last possible place. If you’re familiar with airplanes, it’s the “fly by wire” concept.

This is another way modern IoTThe Internet of Things. A broad term covering many different applications where "things"  are interconnected through the internet. systems are different from the past: even if they have a mechanical part, they are primarily electronic; that’s how the information moves around. Because the info is electronic, it can travel, say, to an actuator directly, or through a hubA piece of electronic equipment that gathers separate related things together. A network hub, for instance, might bring together the individual network connections of multiple local users. A sensor hub brings together sensor data from multiple separate sensors for possible combination. Or, more specifically, a device in the home (or elsewhere) that acts as a central point connecting a variety of smart-home (or other) devices. The devices talk to the hub; the hub talks to the cloud., or even through the cloudA generic phrase referring to large numbers of computers located somewhere far away and accessed over the internet. For the IoT, computing may be local, done in the same system or building, or in the cloud, with data shipped up to the cloud and then the result shipped back down.. That would never be possible in an old-style system that’s all mechanical.

Building Chips

But… if we’re going to understand more about these sensors and actuators, we need to talk first about how silicon chips are made. We’ll keep it at a high level for now – what we talk about could apply both to electronic circuits as well as sensors/actuators. So, once we have that under our belt, then we’ll look at how we can use those tools to make mechanical elements

Which will be easier to understand than talking about how to make electronics. Mechanical tools are familiar from our everyday macro-level life. Electronics need transistors and resistors and all kinds of other things – elements that don’t have ready analogs in our daily lives. So even though engineers might think of mechanical stuff on chips as novel and interesting, for the rest of us, the mechanical stuff will be easier.

So for the next few weeks, we look at semiconductorA material that, under some circumstances, can conduct electricity and, in other circumstances, cannot. processing. Buckle up! (But it shouldn’t be a rough ride…)