AMT Datasouth XL 300 SERIES, Руководство по обслуживанию

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T1 is the current rise period, during which the fun power supply voltage is applied to the
solenoid to build the current up as quickly as possible. T2 is the slow decay or “free
wheeling” period. The supply voltage is removed and current is allowed to re-circulate
through the solenoid. T3 is the fast decay or “fly back” period.
The sequencing of these periods is controlled by timers. When the solenoids are energized
two timers are started. The first timer controls period T1; when it expires, the voltage
source is removed. The second timer controls the transition from T2 to T3. When it
expires, the darlington select transistors are disabled forcing the solenoid into the “fly
back” mode.
2.5: PAPER MOTOR
Paper motion is provided by a 7.5 degree, two phase, permanent magnet stepper motor.
The pin feed tractors are driven by the motor through a timing belt. The motor is geared so
that 8 steps of the motor advance the paper 1/6 of an inch.
The motor is controlled by the microprocessor which provides the step sequencing and
timing functions (see Figure 2.3).
Figure2.3 Paper Motor Current Waveforms
Power is delivered by a chopping current regulator operating off the +55V supply. Power
can be cut off from the motor by disabling the “system ready” (see section on system
clamp). When the printer is idle system ready is disabled by the processor and the motor is
not energized. When the paper feed motor is idle and system ready is enabled, the
amplifier will maintain a holding current of 0.5 amps in each winding of the motor. Any
change at the inputs to the paper feed amplifier (ie. a step command) is detected by the
amplifier which responds by increasing its current limit level. This is achieved by changing
the reference voltage on the comparator in the current limiting circuit.
2-3