FPGA-Field Programmable Gate Array and CPLD-Complex Programmable Logic Device– both are programmable logic devices made by the same companies with different characteristics.
Architecture
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Read MoreIn recent years, the line between hardware and software has blurred. Hardware now engineers create the bulk of their new digital circuitry in programming languages such as VHDL and Verilog. This article will help you make sense of programmable logic.
A quiet revolution is taking place. Over the past few years, the density of the average programmable logic device has begun to skyrocket. The maximum number of gates in an FPGA is currently around 500,000 and doubling every 18 months. Meanwhile, the price of these chips is dropping. What all of this means is that the price of an individual NAND or NOR is rapidly approaching zero! And the designers of embedded systems are taking note. Some system designers are buying processor cores and incorporating them into system-on-a-chip designs; others are eliminating the processor and software altogether, choosing an alternative hardware-only design.
As this trend continues, it becomes more difficult to separate hardware from software. After all, both hardware and software designers are now describing logic in high-level terms, albeit in different languages, and downloading the compiled result to a piece of silicon. Surely no one would claim that language choice alone marks a real distinction between the two fields. Turing's notion of machine-level equivalence and the existence of language-to-language translators have long ago taught us all that that kind of reasoning is foolish. There are even now products that allow designers to create their hardware designs in traditional programming languages like C. So language differences alone are not enough of a distinction.
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Read MoreIntroduction In the days of modern means of obtaining information ,Anyone with amost no knowledge can write code. Even teenagers can sling gates and PAL equations around. What is it that separates us from these amateurs? Do years of college necessarily make us professionals, or is there some other factor that clearly delineates engineers from hackers? With
Read MoreIntroduction
A microcontroller is a computer with most of the necessary support chips
onboard. All computers have several things in common, namely:
with the outside world i.e. connection to devices such as keyboard, mouse,
monitors and other peripherals.
There are a number of other common characteristics that define microcontrollers.
If a computer matches a majority of these characteristics, then it can be
classified as a ‘microcontroller’. Microcontrollers may be:
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Read MoreEverybody knows about atoms and electrons don't they? Well we could skip this part but of course we won't because you will likely learn something new.
Electron theory states all matter is comprised of molecules, which in turn are comprised of atoms, which are again comprised of protons, neutrons and electrons. A molecule is the smallest part of matter which can exist by itself and contains one or more atoms.
If you turn on a light switch for example you will see the light bulb (globe) glow and emit light into the room. So what caused this to happen? How does energy travel through copper wires to light the bulb? How does energy travel through space? What makes a motor turn, a radio play?
To understand these processes requires an understanding of the basic principles. For the light to glow requires energy to find a path through the light switch, through the copper wire and this movement is called electron flow. It is also called current flow in electronics. This is the first important principle to understand.
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Read More• Faraday's Law
• Application of Faraday's Law
• A Single Coil DC Motor
• Motor Constants
Faraday's Law
In the early 1830’s, Michael Faraday and Joseph Henry independently discovered the relationship between changing magnetic fields and induced EMF in circuits. If B is the flux density of a constant magnetic field and a conductor is moved through this field at a velocity V, an EMF E is generated in the conductor such that:
E=BxV
If the conductor is part of a complete electrical circuit with a resistance R, then the EMF will produce a current in the conductor such that:
I = E / R = B x V / R
The development of an EMF in a conductor moving in a magnetic field is the principle on which many types of tachometers are based. By using the commutation
techniques described in the next section, a rotary device can be constructed which has, as its input, a rotary mechanical motion and, as its output, a voltage proportional to that input rotational velocity. Another specific application of Faraday’s Law is used in electric motors. That is, if a conductor of length L carrying a current I is placed in a magnetic field B, a magnetic force F is created such that:
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Motor Calculations |
• Calculating Mechanical Power Requirements
• Torque – Speed Curves
• Numerical Calculation
• Sample Calculation
• Thermal Calculations
Calculating Mechanical Power Requirements
Physically, power is defined as the rate of doing work. For linear motion, power is the product of force multiplied by the distance per unit time.
In the case of rotational motion, the analogous calculation for power is the product of torque multiplied by the rotational distance per unit time.
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Read MoreSelecting a DC motor for a particular application can be a rather involved process . Hower, it is often useful to be able to "ballpark" a motor selection on one's own. A few rules relating to the physics and the practical application of motors should be kept in mind.
The major constraint on motor operation is thermal in nature. The heat a motor must dissipate can always be calculated as follows:
Heat dissipated = current through the motor squared, multiplied by the terminal resistance.
The current through a motor is solely determined by the torque the motor produces. Current and torque are related by the torque constant of the motor.
Current through motor = torque produced divided by the torque constant
Further Considerations:
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Read MoreDC Motor Application Considerations
Audible Noise
Audible noise is a concern in some types of motor applications. In many medical applications like infusion pumps or prosthetic devices, the patient can be very sensitive to the noise disturbance. Good design practice requires that the noise be limited as much as possible. In large machines, the combination of hundreds of DC motors and gears operating simultaneously can be very loud and distracting to the employees who have to work in close proximity to the machine.
Quality Components: Probably the best method of insuring low audible noise in motors is to specify quality components. Motors using cheap or poorly fitted bearings are more likely to be noisy. Poorly designed or loose fitting brush sets can contribute to audibly noisy commutation. Manufacturers of inexpensive, high volume motors cannot reasonably be expected to concern themselves with quiet operation beyond some minimum standard, and the use of such motors in applications where quiet operation is important should be considered carefully. The designer must consider whether low cost takes precedence over quiet operation in the priorities of the customer.
Bearing Choice: The use of ball bearings without pre-load is a potential source of audible noise. Where the specific application permits, ball bearings should be pre-loaded. This means that the balls will not be able to move axially in the race and cause the minute intermittent rattling that can sometime be associated with unpreloaded ball bearings. Smaller ball bearings can be sensitive to heavy shaft loads. They are easily damaged during press fitting added components and by short radial or axial overloads. Care should be taken not to exceed the shaft loading ranges specified in the datasheets. A damaged ball bearing can be a significant source of audible noise and can effect motor life.
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OverView
Stepping motors can be viewed as electric motors without commutators. Typically, all windings in the motor are part of the stator, and the rotor is either a permanent magnet or, in the case of variable reluctance motors, a toothed block of some magnetically soft material. All of the commutation must be handled externally by the motor controller, and typically, the motors and controllers are designed so that the motor may be held in any fixed position as well as being rotated one way or the other. Most steppers, as they are also known, can be stepped at audio frequencies, allowing them to spin quite quickly, and with an appropriate controller, they may be started and stopped "on a dime" at controlled orientations.
For some applications, there is a choice between using servomotors and stepping motors. Both types of motors offer similar opportunities for precise positioning, but they differ in a number of ways. Servomotors require analog feedback control systems of some type. Typically, this involves a potentiometer to provide feedback about the rotor position, and some mix of circuitry to drive a current through the motor inversely proportional to the difference between the desired position and the current position.
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