Posts Tagged ‘resistor’

Determining Patent Eligibility – Part 4, Machines of a Different Kind

Sunday, April 28th, 2013

      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.

engineering expert witness in patent infringement cases

      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.


Transistors – Voltage Regulation, Final Chapter

Monday, November 19th, 2012

     Last time we learned how the transistor opens a path for electric current to flow from the collector to the emitter in our example circuit.  It does so by making use of an unregulated power supply.  Now let’s see how the Zener diode fits into the mix.

transistor series voltage regulator

Figure 1


     It just so happens that bipolar transistors, like the one in our example circuit in Figure 1, are designed so that voltage at its emitter is dependent upon the voltage applied at its base.  This makes them ideal for use in voltage regulator circuits where this kind of predictability is required.

     For example, in our transistor series voltage regulator, the Zener diode is connected to the transistor’s base, B.  When the branch current flows from RLimiting down through the diode, a Zener voltage, VZener, is established.  Since the diode is connected to the transistor, VZener voltage is also applied to the transistor’s base.  Thus the transistor’s emitter voltage will be regulated according to the Zener voltage.

     Bipolar transistors are designed by manufacturers to typically operate with a standardized voltage difference of 0.6 volts between the base and emitter.  This is represented in Figure 1 as VBE, where BE stands for base-emitter.  VBE is standardized at a known quantity of 0.6 volts to simplify things within the industry and aid engineers in their calculations to design transistor circuits, as we’ll now see.

     With the Zener diode connected to the transistor base in our example circuit, the voltage difference is denoted as:

VBE = VZener   VE

where VE is the emitter voltage.  Rearranging terms to solve for VE, we get:

VE = VZener – VBE

Inserting VBE,  which we know is standardized at 0.6 volts:

VE = VZener – 0.6 volts

Since the emitter is physically connected to the output terminal of the transistor series voltage regulator, the emitter voltage is going to be equal to the output voltage, VOut.

     We learned earlier in this series of articles that VZener is a reliable source of consistent voltage.  Because it is present in our transistor series voltage regulator, our example circuit will produce a nice, constant regulated output voltage of VZener – 0.6 volts, a voltage that is useful for many of today’s applications.  However the transistor series voltage regulator provides us with a major advantage over the Zener diode voltage regulator circuit.

     The advantage of a transistor series voltage regulator lies in the fact that  RLimiting is on a separate branch all to its own within the regulator circuit, and because of this it no longer acts as a roadblock to limit the main path of current flow, as happens within the Zener diode voltage regulator circuit discussed previously.  Refer to the red path shown in Figure 1.  With RLimiting in this position the transistor series voltage regulator is able to feed more current to the external supply circuit than is possible through the Zener diode voltage regulator alone.  This means it can be used in more power hungry applications like energizing today’s TVs and modern kitchen appliances.

     That wraps up our discussion on transistors.  Next time we’ll begin a new topic, how medical devices can be designed using systems engineering, a systematic approach that ensures that designed devices satisfy both user and regulatory requirements.



Transistors – Voltage Regulation Part XVII

Monday, November 12th, 2012

     Last time we learned about a new type of transistor called a bipolar transistor and how it controls the flow of electric current traveling from the collector to the emitter within our circuit.  We also saw how the bipolar transistor is integrated within a Zener diode voltage regulator circuit to make a new type of circuit called a transistor series voltage regulator.

     Now let’s see how this all works by hooking our circuit up to both an unregulated power supply and an external supply circuit as shown in Figure 1.

transistor voltage regulator circuit

Figure 1


     When voltage VUnregulated is applied to our transistor series voltage regulator circuit by way of an unregulated power supply, electric current flows through RLimiting into the base, B, of the transistor.  The transistor senses this current and responds by opening a path for current to flow from its collector, C, to its emitter, E.  With this path established, current flows freely from the unregulated power supply, through the transistor’s collector and emitter, on to the output terminal, and finally to the external supply circuit.  Total resistance of this circuit is said to be RTotal

     At this point you’re probably wondering why the bipolar transistor base and Zener diode are connected to RLimiting.  Next time we’ll conclude our series by seeing how this connection is crucial to the functionality of our transistor series voltage regulator.



Transistors – Voltage Regulation Part XV

Sunday, October 28th, 2012

     We’ve been discussing the advantages of using limiting resistors within Zener diode regulating circuits to lessen the probability of circuit failure. Today we’ll continue our discussion, focusing on the Zener diode’s advantages and disadvantages.  See Figure 1.

Zener diode voltage regulator circuit

Figure 1


     Figure 1 discloses the simplicity of a voltage regulator employing a Zener diode.  There are only two components, a limiting resistor, RLimiting, and the Zener diode itself, which also makes the entire assembly cost effective to manufacture. 

     Despite the obvious advantages, there is one major disadvantage to the Zener diode voltage regulator.  Ironically, the limitation imposed by RLimiting on the current IPS itself creates an operational dilemma.  When electronic devices are connected to the output terminals of the regulator, RLimiting  and its current-limiting action becomes a disadvantage.  See Figure 2.

electronic voltage regulator

Figure 2


     The amount of current I available to flow through to electronic devices is limited, sometimes too much, and the net result is that the Zener diode voltage regulator can only be used to power electronic devices drawing small amounts of current.  It is unacceptable for many applications, such as powering kitchen appliances or flat screen TVs.

     Next time we’ll see how to improve upon the Zener diode voltage regulator circuit by adding a transistor.  This will eliminate the road block imposed by RLimiting, thus allowing higher, but still regulated, current to flow through to the output terminals.


Transistors – Voltage Regulation Part XIII

Monday, October 15th, 2012

     Last time we learned how the Zener diode, an excellent negotiator of current, is involved in a constant trade off, exchanging current for voltage so as to maintain a constant voltage.  It draws as much current through it as is required to maintain a consistent voltage value across its leads, essentially acting as voltage regulator in order to protect sensitive electronic components from power fluctuations. 

     Now let’s revisit our example power supply circuit and see how Ohm’s Law is used to determine the amount of electric current, IPS, that flows from the unregulated power supply and why this is important to the function of the Zener diode.  See Figure 1.

power supply

Figure 1


     If you’ll recall, Ohm’s Law states that current flowing through a resistor is equal to the voltage across the resistor divided by its electrical resistance.  In our example that would be IPS flowing through to RLimiting.  In fact, the voltage across RLimiting is the difference between the voltages at each of its ends.

     Applying this knowledge to our circuit, the voltage on one end is VUnregulated, while the voltage at the other is VZener.  According to Ohm’s Law the equation which allows us to solve for IPS is written as:

IPS = (VUnregulatedVZener) ÷ RLimiting

     And if we have a situation where VUnregulated equals VZener , such as when the voltage of an unregulated power supply like a battery equals the Zener voltage of a Zener diode, then the equation becomes:

(VUnregulatedVZener ) = 0

And if this is true, then the following is also true:

IPS = 0 ÷ RLimiting = 0

     In other words, this equation tells us that if VUnregulated is equal to VZener, then the current IPS will cease to flow from the unregulated portion of the circuit towards the Zener diode and the external supply circuit.  Put another way, in order for IPS to flow and the circuit to work, VUnregulated must be greater than VZener.

     Next week we’ll continue our discussion and see why the resistor RLimiting is necessary in order to prevent the circuit from self destructing.


Transistors – Voltage Regulation Part XII

Sunday, October 7th, 2012

     Let’s continue our discussion with regard to the example circuit discussed last time and see how the Zener diode works in tandem with the limiting resistor to control current flow and hold the output voltage at a constant level.

Zener diode voltage regulator

Figure 1


     To recap our discussion from last week, the unregulated power supply portion of the circuit in Figure 1 generates an unregulated voltage, VUnregulated.  Then the Zener diode, which acts as a voltage regulator, takes in VUnregulated and converts it into a steady output voltage, VOutput.  Because these output terminals are connected to the ends of the Zener diode, VOutput  is equal to the voltage put out by it, denoted as VZener.

     The Zener diode, an excellent negotiator of current, is essentially involved in a constant trade off, substituting electric current that originates in the unregulated power supply portion of the circuit for voltage, VOutput, that will serve to power the external supply circuit.   In other words, the Zener diode draws as much current, IZ, through it as it needs, its objective being to keep VOutput at a constant level, and it will continue to provide this constant output, despite the fact that VUnregulated varies considerably.

     So, where does the current IZ come from?  From IPS, that is, the current flowing from the unregulated power supply area, as shown in Figure 1.  

     IPS flows through the limiting resistor to a junction within the circuit.  At this junction, IZ splits off from IPS and continues on to the Zener diode, while current I splits off from IPS on its way to the total internal resistance, RTotal, in the external supply circuit.  

     What this means is that when you add IZ and I together, you get IPS.  Mathematically speaking this is represented as:

IPS = IZ + I

     Why solve for IPS?  We’ll see why this is important when we revisit Ohm’s Law next week and gain a fuller understanding of how IPS, VUnregulated, VZener, and RLimiting relate to each other with regard to the Zener diode.  


Transistors – Voltage Regulation Part VI

Sunday, August 26th, 2012
     Believe it or not as a kid in grade school I used to hate math, particularly algebra.  None of my teachers were able to decipher its complexities and render it comprehensible to me or the majority of my classmates.  Then in high school everything changed.  I had Mr. Coleman for freshman algebra, and he had a way of making it both understandable and fun, in a challenging kind of way.  With 40 years of teaching under his belt, Mr. Coleman knew exactly how to convey the required information in an understandable manner, and to this day I find his insights useful in solving engineering calculations.

      Last time we began our discussion on Ohm’s Law and how it may be applied to our example circuit to solve for the electrical current flowing through it.  Let’s continue our discussion to see how the Law applies to only one part of the circuit.  Then, we’ll use a little algebra to show how the output voltage of an unregulated power supply is affected by changes in RTotal.

electronic power supply

Figure 1


     To help us see things more clearly, in Figure 1 we’ll cover up the inside workings of the unregulated power supply side of the circuit and concentrate on the external supply part of the circuit alone.  Since RTotal is connected to the terminals of the power supply, the voltage applied to RTotal is the same as the power supply output voltage, VOutput.

     In my previous article, we learned that according to Ohm’s Law, the current flowing through a resistance is equal to the voltage applied to it, divided by the resistance.  The fact that RTotal is connected to the two output terminals like we see in Figure 1, allows us to use Ohm’s law to solve for the electrical current, I, flowing through  RTotal:

I = VOutput ÷ RTotal

     Now let’s pull the cover off of the unregulated power supply again to see what’s going on within the circuit as a whole.

electronic circuit

Figure 2


    In Figure 2 we can see that the current, I, flowing through RTotal is the same current flowing through the balance of the circuit.  In the preceding blog we found that value to be:

I = VDC ÷ (RInternal + RTotal)

     We can combine the above two equations for I to develop an algebraic relationship between VOutput and RInternal, RTotal, and VDC:

VOutput ÷ RTotal   =  VDC ÷ (RInternal + RTotal)

     Then, by rearranging terms and applying the cross multiplication principle of algebra we can solve for VOutput.  This involves multiplying both sides of the equation by RTotal:

VOutput =  RTotal × (VDC ÷ (RInternal +RTotal))

     This equation tells us that although RInternal doesn’t fluctuate, VOutput will fluctuate when RTotal does.  This fact is demonstrated in our equation when we make use of algebra.  That is to say, when a term changes on one side of the equation, it causes the other side of the equation to change as well.  In this case, when RTotal  changes, it causes VOutput to change in proportion to the fixed values of VDC and RInternal.

     Next time we’ll look at another shortcoming of unregulated power supplies, more specifically, how one supply can’t power multiple electrical circuits comprised of different voltages. 


Transistors – Voltage Regulation Part V

Sunday, August 19th, 2012
     I’m sure you’ve seen the television commercials warning about harmful interactions between prescription medications.  By the same token electronic circuitry can also be adversely affected by certain combinations of electrical components, as we’ll discuss in today’s blog.

     Last time we looked at a circuit schematic containing an unregulated power supply.  This power supply was connected to an external supply circuit containing a number of components such as electric relays, buzzers, and lights.  Each of these components has a resistance factor, and combined they have a total resistance of RTotal.  We saw that when RTotal increases, the electrical current, I, decreases, and when RTotal decreases, I increases. 

     In contrast to this increasing/decreasing activity of the total resistance RTotal,  the fixed internal resistance of the unregulated power supply, RInternal, doesn’t fluctuate.  Let’s explore Ohm’s Law further to see how the static effect of RInternal  combines with the changing resistance present in RTotal to adversely affect the unregulated power supply output voltage, VOutput, causing it to fluctuate.

unregulated power supply circuit

Figure 1


     In Figure 1 RTotal and RInternal are operating in series, meaning they are connected together like sausage links.  In this configuration their two resistances add together as if they were one larger resistor.  

     Generally speaking, Ohm’s Law sets out that the current, I, flowing through a resistor in an electrical circuit equals the voltage, V, applied to the resistor divided by the resistance R, or:

I = V ÷ R

     In the case of the circuit represented in Figure 1, the resistors RInternal and RTotal are connected in series within the circuit, so their resistances must be added together to arrive at a total power demand.  Voltage is applied to these two resistors by the same voltage source, VDC.  So, for the circuit as a whole Ohm’s Law would be written as:

I = VDC ÷ (RInternal + RTotal)

     But, Ohm’s Law can also be applied to individual parts within the circuit, just as it can be applied to a single kitchen appliance being operated on a circuit shared with other appliances.  Let’s see how this applies to our example circuit’s RTotal next week.


Dynamic Brakes

Monday, May 31st, 2010

     Last week we looked at how a mechanical brake stopped a rotating wheel by converting its mechanical energy, namely kinetic energy, into heat energy.  This week, we’ll see how a dynamic brake works.

     Chances are you have directly benefited by a dynamic braking system the last time you rode in an elevator.  But, to understand the basic principle behind an elevator’s dynamic brake system, let’s first take a look at the electric braking system in Figure 1 below. 

Figure 1 – A Simple Electric Braking System

     Here the brake consists of an electric generator wired via an open switch to an electrical component called a resistor.  The weight is attached to a cable that is wound around a pulley on the generator’s shaft.   As the weight freefalls, the cable unwinds on the pulley, causing the pulley to turn the generator’s shaft.

     Unlike last week’s mechanical brake which required a good deal of effort to employ, a dynamic braking system requires very little.  All that needs to be done is to close a switch as shown in Figure 2 below.  When the switch is closed, an electrical circuit is created where the resistor gets connected to the generator.  The resistor does as its name implies: it resists (but doesn’t stop) the electrical current flowing through it from the generator.  As the electrical current fights its way through the resistor to get back to the generator, the resistor gets hot like an electric heater.  This heat is dissipated to the cooler surrounding air.  At the same time, the weight begins to slow down in its descent.  But how is this happening?

     The electric braking system can be thought of as an energy conversion process.  We start out with the kinetic, or motion energy, of the freefalling weight.  This kinetic energy is transmitted to the electrical generator by the cable, which spins the generator’s shaft as the cable unwinds.  Electrical generators are machines that convert kinetic energy into electrical energy.  This energy travels from the electric generator through wires and a closed switch to the resistor.  In the process the resistor converts the electrical energy into heat energy.  So, kinetic energy is drawn from the falling weight through the conversion process and leaves the process in the form of heat.  As the falling weight is drained of kinetic energy, it slows down. 

 Figure 2 – Applying the Electric Brake   

     Okay, now let’s get back to dynamic brakes on elevators.  An elevator is attached by a cable to a hoist that is powered by an electric motor.  When it’s time to stop at the desired floor, the automatic control system disconnects the elevator’s electric motor from its power source and turns the motor into a generator.  The generator is then automatically connected to a resistor like the one shown in the electric brake above.  The kinetic energy of the moving elevator is converted by the generator into electrical energy.  The resistor converts the electrical energy into heat energy which is then dissipated into the surrounding environment.  The elevator slows down in the process because it’s being robbed of kinetic energy.  When the dynamic brake slows the elevator down enough, a mechanical brake is introduced, taking over to bring the elevator to a complete stop.  This two-fold process serves to reduce wear and tear on the mechanical brake’s parts, lengthening the operational lifespan of the system as a whole.

     Next time, we’ll tie everything together and show how mechanical and dynamic brakes work together in a diesel locomotive.