Micro controller
embedded memory technology:
Since the emergence of
micro controllers, many different memory technologies have been used. Almost all
micro controllers have at least two different kinds of memory, a non-volatile
memory for storing firmware and a read-write memory for temporary data.
Data:
Working memory, with a few more
transistors per bit used in the register file. FRAM or MRAM could potentially
replace it as it is 4 to 10 times denser which would make it more cost
effective.
In addition to the SRAM, some
microcontrollers also have internal EEPROM for data storage; and even ones that
do not have any (or not enough) are often connected to external serial EEPROM
chip (such as the BASIC Stamp) or external serial flash memory chip.
A few recent microcontrollers
beginning in From the earliest microcontrollers to today, six- transistor SRAM
is almost always used as the read/write 2003 have "self-programmable"
flash memory.
Firmware:
The earliest microcontrollers
used mask ROM to store firmware. Later microcontrollers (such as the early versions
of the Frees cale 68HC11 and early PIC microcontrollers) had quartz windows
that allowed ultraviolet light in to erase the EPROM.
The Microchip PIC16C84,
introduced in 1993,was the first microcontroller to use EEPROM to store
firmware.In the same year, Atmel introduced the first microcontroller NOR Flash
memory to store firmware
➢
Stepper motors are digital motors, we actually Send Position signals to
the Motor to drive them.
➢ It is of
four wire stepper motor
A stepper motor or step
motor or stepping motor is a motor that divides a full rotation into
a number of equal steps. The motor's position can then be commanded to move and
hold at one of these steps without any feedback sensor (an open-loop
controller), as long as the motor is carefully sized to the application in
respect to torque and speed.
Switched reluctance motors are
very large stepping motors with a reduced pole count, and generally are
closedloop commutated.
APPLICATIONS:
Computer controlled stepper
motors are a type of motion-control positioning system. They are typically
digitally controlled as part of an open loop system for use in holding or
positioning applications.
In the field of lasers and optics
they are frequently used in precision positioning equipment such as linear actuators,
linear stages, rotation stages, goniometers and mirror mounts. Other uses are
in packaging machinery,and positioning of valve pilot stages for fluid control
systems.
Commercially, stepper motors are
used in floppy disk drives, flatbed scanners, computer printers, plotters,slot
machines image scanners, compact disc drives, intelligent lighting, camera
lenses, CNC machines and, more recently, in 3D printers.
Stepper
motor system:
A stepper motor
system consists of three basic elements, often combined with some type of user
interface (host computer, PLC or dumb terminal):
● Indexers
- The indexer (or controller) is a microprocessor capable of generating step
pulses and direction signals for the driver. In addition, the indexer is
typically required to perform many other sophisticated command functions.
● Drivers
- The driver (or amplifier) converts the indexer command signals into the power
necessary to energize the motor windings. There are numerous types of drivers,
with different voltage and current ratings and construction technology. Not all
drivers are suitable to run all motors, so when designing a motion control
system the driver selection process is critical.
● Stepper
motors - The stepper motor is an electromagnetic device that converts digital
pulses into mechanical shaft rotation. Advantages of step motors are low cost,
high reliability, high torque at low speeds and a simple, rugged construction
that operates in almost any environment. The main disadvantages in using a
stepper motor is the resonance effect often exhibited at low speeds and decreasing
torque with increasing speed.
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