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Servo Motor Terminology:
Enable/Disable:
The ability of a drive to release the motor to freewheel (disabled).
Encoder:
a device that is connected to the motor shaft and measures the motor rotation
in small
increments called ‘lines’ or ‘counts’. These are converted into electrical pulses that are sent to the
servo Drive so that the motor position is known.
Pulse or Signal Multiplier a.k.a
. ‘Electronic Gearing’:
Some drives have the capacity to receive
extremely high speed signals. If the CNC system is not capable of producing a very high speed
signal, an electronic ‘ratio’ is established so that the slower signal is ‘multiplied’ to achieve the very
high data rates needed by the drive. For example, if the multiplier is set at 10, every pulse coming into
the drive is counted as if it were 10 pulses.
RPM and MAX RPM:
Revolutions Per Minute. The speed at which the motor is turning. The
MAXimum for each motor is established by the manufacturer and generally printed on a plate
attached to the motor.
Signals and Hardware Terminology:
A/D Converter:
Computers process and move digital data; however, there is a need, particularly in
instrumentation, like a thermostat, for example, to have analog signals. Most of us are interested in
the temperatures between freezing and boiling for example, so a signal that can represent any value
is needed. Because computers can only process digital signals, passing analog data to a computer
requires an Analog-to-Digital converter, or A/D for short.
Analog Signals:
Like a digital signal, analog represents the values using voltage; but unlike digital,
where you only have high and low, analog can represent everything in between. The voltage is
normally not divided into tiny slices of time like digital, but rather the continuous presence of some
particular variable voltage.
Break Out Board:
Very simple concept. A plug with any tiny pins at each end, such as a typical
printer cable, is a difficult device to connect individual wires to. To solve this dilemma, a BOB simply
has the correct plug for the many pi
ns in the cable connector and ‘Breaks Out’ each of those wires to
an accessible terminal (typically a screw clamp type).
COM Port:
COMmunication ports carry a
Serial
signal
(pulses lined up on a single wire). Also
physically and electronically defined by IBM, but targeted at devices like modems that carry serial
signals
Differential Signals
:
Keyword here is ‘different’. The signal is split into two mirror images and
transmitted across a pair of wires that are twisted together (Twisted pair, or UTP). Unlike single
ended signals which are measured between the signal and ground, differential signals measure the
differential (difference) between the two wires. The operational theory is that any interference would
affect both wires equally and since they are opposite polarity, that interference would cancel itself out.
Far more reliable and having faster available speeds and limited need for shielding. More expensive
and dedicated chips are needed to convert to and from the differential condition.
