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During 6th grade science we had a chapter on Simple Machines, and my textbook listed a common lever as an example, the sort that can be used to make work easier. Its illustration showed a stick perched atop a triangular shaped stone, appearing very much like a teeter-totter in the playground. A man was pushing down on one end of the stick to move a large boulder with the other end. Staring at it I thought to myself, “That doesn’t look like a machine to me. Where are its gears?” That day I learned about more than just levers, I learned to expect the unexpected when it comes to machines.
Last time we learned that under patent law the machine referred to in federal statute 35 USC § 101 includes any physical device consisting of two or more parts which dynamically interact with each other. We looked at how a purely mechanical machine, such as a diesel engine, has moving parts that are mechanically linked to dynamically interact when the engine runs. Now, lets move on to less obvious examples of what constitutes a machine. Would you expect a modern electronic memory stick to be a machine? Probably not. But, under patent law it is. It’s an electronic device, and as such it’s made up of multiple parts, including integrated circuit chips, resistors, diodes, and capacitors, all of which are soldered to a printed circuit board where they interact with one another. They do so electrically, through changing current flow, rather than through physical movement of parts as in our diesel engine. A transformer is an example of another type of machine. An electrical machine. Its fixed parts, including wire coils and steel cores, interact dynamically both electrically and magnetically in order to change voltage and current flow. Electromechanical, the most complex of all machine types, includes the kitchen appliances in your home. They consist of both fixed and moving parts, along with all the dynamic interactions of mechanical, electronic, and electrical machines. Next time we’ll continue our discussion on the second hurtle presented by 35 USC § 101, where we’ll discuss what is meant by article of manufacture. ___________________________________________ |
Posts Tagged ‘electronic device’
Determining Patent Eligibility – Part 4, Machines of a Different Kind
Sunday, April 28th, 2013
Transistors – Voltage Regulation Part VIII
Sunday, September 9th, 2012| Back in the early 1970s my dad, a notorious tightwad, coughed up several hundred dollars to buy his first portable color television. That was a small fortune back then. The TV was massive, standing at 24 inches wide, 18 inches high, and 24 inches deep, and weighing in at about 50 pounds. I think the only thing that made this behemoth “portable” was the fact that it had a carrying handle on top.
A major reason for our old TV being so big and clunky was of course due to limitations in technology of the time. Many large, heavy, and expensive electronic components were needed to make it work, requiring a lot of space for the circuitry. By comparison, modern flat screen televisions and other electronic devices are small and compact because advances in technology enable them to work with far fewer electronic components. These components are also smaller, lighter, and cheaper. Last time we looked at the components of a simple unregulated power supply to see how it converts 120 volts alternating current (VAC) to 12 volts direct current (VDC). We discovered that the output voltage of the supply is totally dependent on the design of the transformer, because the transformer in our example can only produce one voltage, 12 VDC. This of course limits the supply’s usefulness in that it is unable to power multiple electronic devices requiring two or more voltages, such as we’ll be discussing a bit further down. Now let’s illustrate this power supply limitation by revisiting our microprocessor control circuit example which we introduced in a previous article in this series on transistors.
Figure 1
In Figure 1 we have to decide what kind of power to supply to the circuit, but we have a problem. Sure, the unregulated power supply that we just discussed is up to the task of providing the 12 VDC needed to supply power for the buzzer, light, and electric relay. But let’s not forget about powering the microprocessor chip. It needs only 5 VDC to operate and will get damaged and malfunction on the higher 12 VDC the current power supply provides. Our power supply just isn’t equipped to provide the two voltages required by the circuit. We could try and get around this problem by adding a second unregulated power supply with a transformer designed to convert 120 VAC to 5 VAC. But, reminiscent of the circuitry in my dad’s clunky old portable color TV, the second power supply would require substantially more space in order to accommodate an additional transformer, diode bridge, and capacitor. Another thing to consider is that transformers aren’t cheap, and they tend to have some heft to them due to their iron cores, so more cost and weight would be added to the circuit as well. For these reasons the use of a second power supply is a poor option. Next time we’ll look at how adding a transistor voltage regulator circuit to the supply results in cost, size, and weight savings. It also results in a more flexible and dependable output voltage. ____________________________________________ |
Transistors – Voltage Regulation Part II
Sunday, July 29th, 2012| I joined the Boy Scouts of America as a high schooler, mainly so I could participate in their Explorer Scout program and learn about electronics. I will forever be grateful to the Western Electric engineers who volunteered their personal time to stay after work and help me and my fellow Scouts build electronic projects. The neatest part of the whole experience was when I built my first regulated power supply with their assistance inside their lab. But in order to appreciate the beauty of a regulated power supply we must first understand the shortcomings of an unregulated one, which we’ll begin to do here.
Last time we began to discuss how the output voltage of an unregulated power supply can vary in response to power demand, just as when sprinklers don’t have sufficient water flow to cover a section of lawn. Let’s explore this concept further.
Figure 1
Figure 1 shows a very basic representation of a microprocessor control system that operates three components, an electric relay (shown in the blue box), buzzer, and light. These three components have a certain degree of internal electrical resistance, annotated as RR, RB, and RL respectively. This is because they are made of materials with inherent imperfections which tend to resist the flow of electric current. Imperfections such as these are unavoidable in any electronic device made by humans, due to impurities within metals and irregularities in molecular structure. When the three components are activated by the microprocessor chip via field effect transistors, denoted as FET 1, 2 and 3 in the diagram, their resistances are connected to the supply circuit. In other words, RR, RB, and RL create a combined level of resistance in the supply circuit by their connectivity to it. If a single component were to be removed from the circuit, its internal resistance would also be removed, resulting in a commensurate decrease in total resistance. The greater the total resistance, the more restriction there is to current flow, denoted as I. The greater the resistance, the more I is caused to decrease. In contrast, if there is less total resistance, I increases. The result of changing current flow resistance is that it causes the unregulated power supply output voltage to change. This is all due to an interesting phenomenon known as Ohm’s Law, represented as this within engineering circles: V = I × R where, V is the voltage supplied to a circuit, I is the electrical current flowing through the circuit, and R is the total electrical resistance of the circuit. So, according to Ohm’s Law, when I and R change, then V changes. Next time we’ll apply Ohm’s Law to a simplified unregulated power supply circuit schematic. In so doing we’ll discover the mathematical explanation to the change in current flow and accompanying change in power supply output voltage we’ve been discussing. ____________________________________________ |
Transistors – Digital Control Interface, Part IV
Monday, July 9th, 2012| The Olympic Torch relay, soon to culminate in London, is the grand daddy of all relays, starting in one country, traversing many others, then ending its journey at the site of the Olympic Games. It passes through many athletes’ hands while on its journey, its final purpose being to light the Olympic Flame. Less glamorous, though still useful, is the relay race that often takes place within digital controls.
Last time we looked at my design solution for the control of a microprocessor controlled medical x-ray film developing machine, where a field effect transistor (FET) acted as a digital control interface between a 5 volt direct current (VDC) microprocessor and a 12 VDC buzzer. Well, controlling the buzzer wasn’t the only function of the microprocessor. It also had to control a 120 volt alternating current (VAC) drive motor, the purpose of which was to move x-ray film through a series of processes within the machine. Yet another requirement was that the machine’s drive motor run 40 minutes upon activation by a start button, then shut off. One of the challenges presented by this specification was that an FET standing alone is only suited to control direct current devices like the buzzer, but not alternating current devices like electric motors. Direct current flows in one direction only when traveling through wire, and since an FET can only pass current in one direction it is the perfect match for those applications. Now, as the name would imply, alternating current flow alternates, that is, it reverses direction and varies in intensity many times each second. This is a scenario that FETs are not equipped to handle because they can’t deal with reverse flow. This meant that, for the purpose of my developing machine, I could not use an FET to directly control the 120 VAC motor. Now let’s take a look at Figure 1 to get a basic look at how I solved the problem. |
Transistors
Sunday, June 10th, 2012| Back in the 60s my dad spent about $25 to buy a small transistor radio. That was a lot of money in those days, but well worth it. The new transistor technology allowed for a much less cumbersome radio to be produced. No more lugging around big radios armed with heavy vacuum tubes. In the years that followed the word transistor became a household word. They were employed in a variety of ways within televisions and other electronic devices, increasing both their reliability and functionality.
So what is a transistor and what does it do? It’s an electronic component, developed in the late 1940s. The first transistor was about as big as a softball and crudely made. As such, it was too impractical for commercial use. Then in the l950s technological advancements made commercial production of smaller, high-quality transistors possible. Transistors enjoyed widespread introduction to the consuming mainstream in the l960s, and since then they’ve been made in many different types, shapes, and sizes. Some are shown in Figure 1 below. Figure 1
A commonly used type of transistor is called a field effect transistor, or FET, one of which is shown in Figure 2. The FET has three metal leads which allow it to be connected into electrical circuits. These leads are referred to as the drain (D), the source (S), and the gate (G).
Figure 2
FET’s control the flow of current within an electronic circuit. A good way to understand what they do is to consider the analogy of water flowing through a faucet.
Figure 3
Figure 3 shows a faucet, complete with valve and handle. With the valve closed the flow of water is completely shut off. If the valve is opened partway by rotation of the handle, a trickle of water emerges. The more the handle is turned and valve is opened, the greater the flow of water. The FET shown in Figure 4 operates a lot like a faucet, but with regard to electrical current. Figure 4
The FET controls the flow of current flowing through its D and S leads, but it does not employ a valve or handle to do it. Rather, flow rate is controlled by application of a small amount of voltage to the G lead. The voltage’s influence on the G lead influences the FET to permit current to flow in through the D lead, then out through the S lead. The amount of voltage applied to the G lead is directly related to how much current will be allowed to flow. In this example the D lead on the FET is connected to a 10 volt direct current (VDC) power supply. The S lead is connected to a flashlight bulb which is connected to electrical ground. If you will remember from previous blogs, electric current naturally wants to flow from the supply source to ground, much like water wants to naturally flow downhill. If the bulb was connected directly to the 10 VDC power supply, current would flow through unimpeded and the bulb would light. However, in Figure 4 the FET acts as a regulating device. It’s connected between the 10 VDC power supply and the bulb. When no voltage is applied to the G lead the FET acts like a closed valve and current is unable to flow. Without current we, of course, have no light. When a low amount of voltage, say one volt, is applied to the G lead, the FET acts like a partially opened valve. It permits a trickle of current to flow from the 10 VDC supply to the bulb, and the bulb glows dimly. As voltage to G increases the FET valve opens further, permitting more current to flow. The bulb glows with increasing brightness. When the voltage applied to G increases to the point the FET valve is opened fully, in our example that is 2 volts, full current is allowed to flow from the 10 VDC supply to the bulb. The bulb glows brightly. Generally speaking, the voltage required to be applied to G for control of current flow through an FET depends on overall design and the particular application within an electrical circuit. FETs are often used within electronic devices to turn things on and off, with no other function in between. Next time we’ll look at some example circuits to see how it’s done. ____________________________________________ |
Ever Had a Wall Wart?
Sunday, August 28th, 2011|
You might have had warts on your skin. They’re formed by viruses making a new home. If you’ve ever had one, you probably didn’t like it and found it hard to get rid of. Walls often have warts, too, although you probably didn’t identify them as such. “Wall Wart” is engineering talk for the black plastic protrusions you often find attached to the exterior of a wall outlet in modern homes. If you call them anything at all, it’s most likely “AC power adapters.” A typical wall wart is shown in Figure 1.
Figure 1 – A Typical Wall Wart Wall warts provide a handy, portable and easy to use conversionary power source for small electronic devices, including lamps, small appliances, and various modern day electronics. If you’re like me, you have lots of them scattered on the walls of your home and office. Most people come to use them when a need arises, say you bought a scanner for your computer. Beyond that they’re usually not given much thought, but today we’re going to explore them a bit. Suppose you’re an engineer and you’ve been asked to design an electronic product for household use. The product only requires 12 volts of direct current (DC) to operate, but you know that the typical home is wired to supply 120 volts of alternating current (AC). What can be done to rectify the discrepancy? Well, there are two distinct choices. One of the choices is to design electronic circuitry capable of converting 120 volts AC into 12 volts DC, then place it inside the product. But is this the best choice? Not really. It takes time to design custom circuitry, and doing so will add substantially to the design time and final cost of the product. This is especially true if the circuitry is produced in small quantities. Besides, if the electronic product is small, there may not be enough room inside to accommodate this type of circuitry. The smarter choice would be to buy a wall wart from another company that specializes in manufacturing them. They’re produced in huge quantities, so the cost is low. They also come in standard voltages, like 12 volts DC. And because the wall wart is external to the product housing, space inside is no longer a concern. It couldn’t be any easier or cost effective. Just plug the wall wart into your home electrical outlet, then plug in the product’s 12 volt DC cord. Done! Next time we’ll take a look at what’s going on inside your basic wall wart to see how it works. ____________________________________________
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Wire Size and Electric Current
Sunday, March 13th, 2011| Whether or not you live or work in a city, you are probably aware of rush hour traffic and how frustrating it can be. As a matter of fact, this traffic is the number one reason many choose to live within cities providing public transportation. Instead of watching the cars pile up in front of you, you can be checking your email or reading the paper. And no matter where you live, you’ve probably encountered a narrow one-lane road at some time. If this road were to be spotted with traffic lights and double parked cars, the resulting frustration would reach a new high, one which has you craving the freedom of a crowded three-lane expressway. At least there’s the possibility of movement there.
Generally, the wider the road and the fewer the impediments, the better traffic will flow. The problems presented by vehicular traffic are analogous to those present in electrical wires. For both, obstructions are impediments to flow. You see, the thicker the metal is in a wire, the more electrical current it can carry. But before we explore why, let’s see how electric wires are classified. If you’ve ever spent any time hanging around a hardware store looking at the goodies, you’ve probably come across wire gauge numbers, used to categorize wire diameter. American Wire Gauge (AWG) is a standardized wire gauge system, used in North American industry since the latter half of the 19th Century. Handy as it is, the AWG gauge numbering system seems to go against logic, because as a wire’s diameter increases, its gauge number decreases. For example, a wire gauge number of 8 AWG has a diameter of 0.125 inches, while a gauge number of 12 AWG has a diameter of 0.081 inches. To make things easier on those who need to know this type of information, wire diameter is tabulated for each AWG gauge number and readily available in engineering reference books. So what does this have to do with electric current? To begin with, the larger the AWG number, the less current it can safely carry. If we turn to an engineering reference book, and look up information relating to an 8 AWG insulated copper wire, we find that it can safely carry an electrical current of 50 amperes, while a 12 AWG insulated copper wire can safely carry only 25 amperes. This information allows us to make important and relevant design decisions regarding a myriad of things, from electrical wiring in electronic devices, to appliances, automobiles, and buildings. So, why are bigger wires able to carry more current? Well, as you’ve heard me say before, no wire is a perfect conductor of electricity, but some metals, take copper for instance, are better conductors than others, say steel. But even the best conductors are inherently full of impurities and imperfections that resist the flow of electricity. This electrical resistance acts much like traffic lights and double parked cars that impede the flow of traffic. The larger the diameter of the wire, the less electrical resistance is present. The logic here is simple. Wire that is larger allows more paths for electrical current to flow around impurities and imperfections. The congestion present in rush hour traffic results in travel delays and hot tempers, and heat is also present in electric wires that face resistance to electricity flow. If the resistance to electric current flow is high enough, it can cause overheating. Road rage within the wires is a possibility, and if the wires get hot enough, electrical insulation can melt and burn, creating a fire. Known as the “Joule heating” effect, this phenomenon is responsible for its share of building fires. We’ll learn more about Joule heating and how wires are sized to keep electrical current flow within safe limits next week. Until then, try to keep out of traffic. _____________________________________________
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