RS-485 for Stepper Motors
RS-485 is an
electrical-only standard, in contrast to complete interface standards which define physical,
functional, and electrical specifications. RS-485 signaling can be used with
many protocols such as Profibus, Interbus, Modbus, or BACnet, depending on the requirements of
the end user. Sometimes controller area network (CAN) or EtherNet are preferred for network
requirements. RS-485 has a 10 Mbps maximum data rate (@ 40 feet) and a 4000 foot maximum cable
length (@100 kbps.) RS-485 is robust and well suited for long distance networking in noisy
environment.
CAN Products for Stepper Motors
CAN is an acronym for
Controller Area Network and refers to a fault-tolerant communications protocol
that is flexible for system design, supports multiple network topologies, and has become a de
facto standard for high integrity serial communications in industrial and automotive embedded
applications. In a CAN network, several short pieces of data like a motor’s run
status, temperature, or RPM is broadcast over the entire network at up to 1 megabit per second
(Mbps.) CAN is meant for applications that have to report and consume numerous
but small pieces of data consistently among nodes and has the ability to self-diagnose and
repair data errors. CAN is well-suited to environments with machinery, since CAN is designed to
be reliable in rugged environments that include interference or introduce noise. CAN is also
well-suited to the transportation industry.
USB Products for Stepper Motors
USB is a standard
connection interface between computers and digital devices. A USB transceiver
is a physical layer device that prepares data for transmission and then sends to, and receives
data from, another transceiver. The transceiver detects connection and provides
the low level USB protocol and signaling. The term "transceiver" indicates an
implementation of both transmit and receive functions. It transmits and receives, encodes and
decodes data, provides error indication, implements buffers to stage data until it can be
managed, and adjusts for the clock rate from the serial stream on the USB SuperSpeed
bus to match that of the “link layer” higher up on the communication stack.
USB Receptacles for Stepper Motors
USB plugs
and receptacles are designed to reduce human error by their unique shape; they
fit together in only one way. USB plugs and receptacles are Type A (connecting to hosts or hubs)
or Type B (connecting to devices) and are available 3 sizes: standard, mini, and micro.
Type A plugs always face upstream, Type B faces downstream.
USB is used in many applications covering all areas of electronics that require
communication, but more commonly with devices that need fast or easy connections for interaction
with computers. Since USB provides a small charging current as well, it is
becoming a de facto standard for charging portable devices.
ESD for Stepper Motors
Electrostatic Discharge
(ESD) is a naturally occurring phenomenon. If you have ever been zapped by a
socks-wearing kid who has just discovered static charge build up, you have experienced ESD first
hand. ESD is like a miniature, localized lightning bolt caused by an electrical
discharge. ESD can have seriously damaging effects on an integrated chip or
system and cause poor performance or failure later on by merely weakening the circuits.
LCD Displays for Stepper Motors
LCD means
"liquid crystal display." It is an electronically driven flat panel screen that
orients liquid crystals within the panel in a direction that blocks or transmits light coming
from behind the panel. LCDs are a low cost, energy efficient visual display
that can be controlled in segments or as individual pixels, in shades of black and gray or in
full color. LCDs have most commonly replaced bulky cathode ray tubes in televisions and
computers and are available in all sizes. Liquid crystals were first discovered in 1888, but
were first put into common use in the early 1970s as electronic digital-display watches.
Switches for Stepper Motors
Switches are
devices that provide manual input or control for equipment, a device, or a process.
Switches serve many purposes, provide immediate emergency control, local
control, or indication; and are available in many formats, shapes, sizes, and colors.
Switches and buttons are important in everyday use from light switches or
buttons to automatic switches that shut off a motor when an attached gate has fully shut.
DC / DC Regulators for Stepper Motors
DC/DC
regulators are circuits that convert DC voltage from one level to another and
maintain that voltage to a constant level. Electronic systems often have several sub-circuits,
each with its own voltage level requirement that may be higher or lower than the main power
supply. Step-up converters or regulators boost a voltage to a higher level. Step-down
converters or regulators lower (or “buck”) a voltage to a lower
level. DC/DC converters and controllers can also be used for
the same purpose, but may offer options such as multiple softstart levels, undervoltage lockout,
protection against overvoltage and undervoltage, and programmable short-circuit protection. All
of these devices are considered to be in the same category of integrated chips, typically
categorized as power management devices.
Digital Isolation for Stepper Motors
Isolation
is critical to protect both an electronics system and the user from potentially hazardous
voltages, or where a high level of electrical isolation between electronics systems is
necessary. Digital isolators are known for their speed of data transmission, high level of
magnetic immunity, and long life expectancy. Used in combination with isolated power supplies,
these devices protect circuits from high voltages, prevent current flow between remote system
grounds, and avoid the creation of current loops. Digital isolators can be used
to implement isolation in designs without the cost, size, power, performance, and reliability
constraints found with optocouplers.
Processors for Stepper Motors
The term
"processor" refers to an electronic device that performs computational
functions and carries out the instructions of a stored program. Other terms for
processor are microprocessor, central processing
unit, and digital signal processor. Essentially, the processor
refers to "the brains of a computer."
Drivers for Stepper Motors
Designers of power electronic
circuits must often drive power switches that feed DC, AC, or power signals to a variety of
workloads. Logic-level electronic circuits provide the driving signals. In general, however, the
power sources and their loads have reference levels different from that of the control circuitry
(ground). MOSFET selection begins by choosing devices that can handle the required current, then
giving careful consideration to thermal dissipation in high current applications.
ADCs for Stepper Motors
An Analog-to-Digital
Converter (ADC or A/D converter) measures the
magnitude of an input analog signal and converts it to a digital number that is proportional to
the magnitude of the voltage or current. An ADC often converts signals
collected from the real-world to digital signals for processing. One of the more important
specifications of an ADC is the resolution that it offers, which is the number of discrete
values (represented in bits) that the ADC produces in relation to the analog
signal it is converting. The more bits, the higher the resolution. A higher resolution yields a
more accurate approximation of the analog input.
Power Stage for Stepper Motors
Some applications must feed high
levels of current and voltage to power heavy electrical loads. The power stage
is a circuit of electronically-controlled transistors that act as high current switches. In
applications powering heavy loads, the power stage is the driving force.
MOSFETs or IGBTs are commonly used in a "bridge" configuration
to drive motors. Selection for the power stage begins by choosing devices that can handle the
required current, and careful consideration must be given to thermal dissipation.
MOSFETs and IGBTs are transistors capable of withstanding the
duty of switching high power signals, and mean "metal–oxide–semiconductor field-effect
transistor" and "insulated gate bipolar transistor", respectively.
Amplifiers for Stepper Motors
A precision
amplifier is used for sensors to preserve accuracy. It increases
the amplitude of weak signals it receives while introducing as little noise as possible so that
the signal transfers an accurate or precise measure of what it is sensing. Amplifiers
have enormous voltage gain, often use feedback of the output signal back to the input
of the amplifier to operate, and can be classified in different ways. An
amplifier can be identified by the device they are intended to drive (e.g.,
audio amplifier), the input that they are to amplify (e.g. sensing amplifier), the frequency
range of the signal (e.g., RF, audio), and by the function that they perform (e.g. buffer
amplifier, current-sensing amplifier.)
Temp Sensors for Stepper Motors
A temperature
sensor is a device that measures cold or heat as a temperature or temperature
gradient. Many applications require some implementation of temperature sensing and measurement.
For motors, the operating temperature inside the case is monitored by the processor and set to
alarm or shut down at temperatures higher than the normal operating temperature of the
motor. If a motor runs at too high of a temperature for too long, it can reduce the
life of the motor. Operating temperature is an indication of the general operating health of the
motor. Higher temperatures inside the motor case can mean too high of a load is placed on the
motor, since as load increases, motor current consumption increases to meet the load
requirements.
Hall Effect for Stepper Motors
Hall Effect
sensors are magnetically biased transducers that vary output voltage or current in
response to changes in a magnetic field. Hall Effect sensors can be designed to
sense rotary movement of a motor shaft. The rotation of the motor shaft changes the IC's
position with respect to the magnets, and thus detects the change in flux density. The output of
the IC is converted to a linear output over 90 degrees of shaft travel. The Hall Effect
sensor gets its name from Edwin Hall, who, in 1879 discovered that a voltage
difference can be produced across an electrical conductor where the magnetic field is
perpendicular to the direction of current flow.
Encoders for Stepper Motors
An encoder, when
used with motors, is an electro-mechanical apparatus that translates the angular position of the
shaft of the motor into an electronic signal that a processor can understand. The information is
then used to calculate and report on speed of the motor, distance, revolutions per minute (RPM)
or position, usually for the purpose of automatic feedback control, some kind of intervention,
or shutdown.
