CENTENT MOTION CONTROLLER
Figure 14, Input circuit
The circuit diagram for a typical
input is shown in Figure 14. The
input device is a 74HC540 octal
inverting buffer. Its outputs go to
the CN0170 data buss while its
inputs go to the Control Connector.
The 2.2K resistor provides input pull-up to the 5 volt supply. This insures
good noise immunity if the inputs are left open, or in the inactive, logical
'1' state. The 220 ohm resistor limits the indicator LED current to 12
milliamps while the input is grounded, or in the active, logical '0' state.
Suitable input devices must be capable of shorting at least 12 milliamps of
current to ground. This includes SPST switches, open collector NPN
transistor circuits, Hall-effect sensors, reed relays, optical isolators and
other devices. More than one switch may be wired to an input. For
example, it may be useful to wire multiple switches to a FLT (fault) input,
permitting the detection of a number of malfunctions.
HME X, Y: (pin 17, pin 4)
The HME input is used in conjunction with the "XH" or "YH" instruction to
calibrate the motor to a known, physical location. Most step motor
applications are open loop; the motor's position is inferred by adding or
subtracting step pulses to the internal position register. It is assumed the
motor will take the steps sent to it.
If a motor fails to take a step, or takes some extra ones, the position
register will be in error with respect to the actual motor position. This error
is accumulative because open loop operation does not feed back to the
controller any motor position information.
A home instruction is used to clear possible errors between where the
CN0170 assumes the motor is and where it actually is. It is usually
invoked before a series of positioning moves are made. This is
accomplished by driving the motor towards a switch that activates the
HME input. The HME input switch is usually activated by the mechanism
driven by the motor.
The CN0170's homing algorithm causes the motor to stop within one
increment of motion of the HME input edge transition. The internal motor
position register is then set to zero; defining the motor's home location.
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Summary of Contents for CN0170
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