Monday, June 06, 2016

Robotics for Gardeners and Farmers, Part 2

In Part 1 of this series I said "you can combine purchased bits with your own bits to create novel devices that perform tasks for which no off-the-shelf solution exists." But why bother, right? Isn't it just a matter of time? Perhaps, but this is something of a chicken-and-egg problem. Investment follows the perception of a potential market. Without the perception of a market into which to sell the fruits of product development, investment is hard to come by, hence little development happens and few products are forthcoming. To really get behind the application of robotics to horticulture and agriculture, in a manner that takes full advantage of the potential of robotics to leverage the very best practices and make them scalable, investors must be convinced that their money will at least accomplish something worthwhile, and preferably that it will bring them a nice return. One way you can contribute to creating that perception of a market is by pushing the envelope of what can be done with what's available now, measuring the results, and talking about it, with friends and neighbors and on the social networks of your choice, preferably accompanied with video that makes clear what your creations do. (I'll come back to the use of social networks later in this installment.)

As I was saying at the close of Part 1, before I can go into much more detail, some additional definitions are in order.

I'm fond of this word in its informal sense, but, as applied to computers and related technologies, a bit is the smallest unit of information, usually represented by a single binary digit, which can have either of two values, 0 or 1. A bit can represented physically in many ways, the side of a coin facing up after a toss, for example. It is typically represented electronically by either a high state (a measurable voltage, either + or -) or a low state (usually ground), and while the signal (see below) representing a bit might be constant until changed, it is more commonly compact in time, and both created and retrieved in reference to a clock signal (see second item below).

Four bits taken together are called a nibble, represented by a 4-digit binary number, which can have any of 16 values: 0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111, 1000, 1001, 1010, 1011, 1100, 1101, 1110, or 1111. These sixteen values can each be represented by a single hexadecimal (base 16) digit: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F, respectively. When combining longer strings of binary digits, such as two nibbles to form a byte (8 bits), the use of hexadecimal becomes first a convenience, then a necessity, as longer strings of 0s and 1s are very difficult to parse visually — hexadecimal 00 is equivalent to binary 00000000, and hexadecimal FF is equivalent to 11111111.

About thirty years ago, a very bright man posed the question (paraphrased), given that computer monitors were typically higher quality than televisions why were the images they produced so much more primitive than those produced by TVs? The answer was all about the source of the signals each was being fed. Television signals, at that time, were derived almost entirely from imagery captured from the physical world, whereas the images on monitors had to be generated by the computers they were attached to. There was no contest; even the supercomputers of that time simply weren’t up to the task of generating life-like imagery in real time; rather they would spend minutes or hours calculating each frame, and even then the result was cartoonish at best. These days smartphones and game consoles do a passable job of generating moving points of view within dynamic 3-dimensional environments of nontrivial complexity.

Like the simplest form of sensor, the simplest signal is either on or off. The signal from a light switch is either nothing at all or a connection to a power source, usually alternating current (AC) with a voltage (in the U.S.) between 110 and 120. The on/off supply of power to the light is, in that example, inseparable from the on/off signal, but what if the switch only controls the supply of power to a relay (a type of magnetic switch controlled by a small direct current running through a coil of wire), which in turn controls the supply of power to the light. In this case the power to the light is distinct from the signal (the power to the relay) that controls it, although that signal is still of the simplest, on/off type. This becomes more clear if we use another sort of relay, one that is closed (on) by default, making a connection unless there is a current through its magnetic coil, such that the light is on when the switch is off, and off when the switch is on.

Signals may be combined with the supply of power, but they are about the representation/encoding and transmission of information, and signal processing is about the extraction/decoding of information from incoming signals.

Under ideal conditions, the voltage of the AC power arriving to your home from the grid, graphed over time, forms a constant sine wave, with a cycle time (in the U.S.) of 1/60 second. Any perturbations from that perfect sine wave carry information, perhaps from a switch being turned on or off within your home, or perhaps from an event happening elsewhere, even many miles away. Background information of unknown significance from an indeterminate source is usually referred to as noise, although at some epistemological peril. (The constant snow we used to see on tube-type televisions attached to antennas, when they were tuned to an unused channel, turned out to be the background radiation left over from the Big Bang.)

Two common ways of encoding information into an AC signal are amplitude modulation (varying the voltage) and frequency modulation (varying the frequency or cycle time), from which the AM and FM radio bands get those names.

Digital devices use a different kind of signal, one more like that of a simple switch, but switching back and forth many times per second. The simplest form of such a signal is called a clock. A clock signal is a constant square wave, rising abruptly, remaining in a high state for an instant, then falling abruptly, remaining in a low state for another instant, over and over in a regular rhythm. Such a clock signal is a reference against which other signals are measured, governing the encoding of information into them and the extraction of information from them.

Serial vs. Parallel
Electronic representation of multi-digit binary numbers can be either serial (one bit at a time) or parallel (several bits as separate signals on separate channels), or both (several bits at a time, combined with a clock signal). Nearly every computer in existence today moves bits around internally at least 4 at a time, and more commonly 32 or 64 at a time, to the beat of a clock running at millions or billions of cycles per second. Externally, over cables and wireless connections between devices, sending one bit at a time is the rule, and sending groups of bits together in lockstep is the exception. Many bits are sent as a string, over such connections, and then reconstituted at the other end.

One place where you will find external connections with 4, 8, or even 16 bits in parallel is on the pins of solder pads provided on single board computers for hobbyists, such as the Raspberry Pi. These are typically configurable, capable of operating either singly or together as a group, in parallel, and can frequently also handle analog signals, in which the information content is encoded as a voltage that varies anywhere between ground state and high state, or, more commonly, pulse width modulation (PWM), in which the information is encoded in the timing of changes between ground state and high state.

That's enough technical talk for one installment. Now back to the discussion of social networks. Even if talk of bits, bytes, processors, and signals leaves you numb, you can act on what follows.

The most important social network is your friends, neighbors, and those you interact with through face-to-face meetings. Find out which of the people in your network is interested in and/or has some competence in technology, either the technologies used in robotics or the biology-based technologies used in organic gardening, agroecology, biological agriculture, or whatever you prefer to call it. Chat them up; find out what they know and what they're interested in, particularly what they're interested in doing themselves. Also find out which online social networks (Facebook, Twitter, etc.) they use, and get connected to them there.

Build on that base. Share your discoveries and projects with this group, and keep up with what they share. If they've done something particularly impressive, maybe do a video-recorded interview and post that. Also nudge your contacts to build out the network by including others they know. Be on the lookout for other such networks, whether intentional or not, and hook up with them as you find them, also any interested individuals you locate online.

Find out if your school or school system has any robotics activities. If you have children, see whether they’re interested. Either way, introduce yourself to the instructor or club sponsor. Chances are they know a few technically adept youth, who would be enthusiastic for a chance to do something real that mattered.

Also introduce yourself to any industrial arts teachers. Robots aren't only computers, but have mechanical components which are essential to what they do, and not all such components can be 3D printed in plastic. Sometimes you might need someone with access to a lathe or a welder or a furnace capable of melting metal for molding, and the skills to use it.

And finally, bug the equipment dealers around you for smaller, lighter, more intelligent, more detail-oriented, less destructive options. Tell them you want to get away from packing down and tearing up the soil, and away from the use of poisons of all types. If they hear this often enough, they'll be passing the message up the chain to their suppliers.

Keep notes, whether on paper or on the device or cloud of your choice, so you don't lose track of what you've already learned.

Get back to contacts periodically.

Not what you were expecting? As I was saying, the perception of a market is critical in motivating investment, and investment can vastly accelerate the development of technology. But money doesn't sit around for long; it gets invested one way or another, into the best option of which the investor is aware. To attract that investment, it's important to make some commotion.

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