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18. Temperature & Motor Control Module R764203
MTR_SEL
DIR
SPD
Image 18-4
Motor drive
Two controlling signals are formed out of a direction signal and a speed signal. The latter is a PWM-signal that can reduce the
velocity of the motor by decreasing the duty-cycle. A switch at each end of the run will break the circuit and stop the motor but a
diode still enables the reverse direction. The current limiting circuit prevents the motor from overheating during an overload situation.
If this persists for more than three seconds then the current supply will be removed. This status can only be reset by selecting the
other direction or a different motor.
Motors with encoder issue two phase-shifted signals, which can be used to increment or decrement a counter, thus keeping track
of the relative position.
Image 18-5
Motor drive
PWM = Pulse Width Modulation: fixed frequency, varying duty-cycle (high/low ratio)
Controller
The voltages from the temperature-sensing circuits are converted with 8-bit ADC's. These values are then used to turn on/off the
proper TEC-signals, and can be read out by the processor. When a DMD goes out of its operating temperature range for more than
two seconds, an interrupt request will be sent out to the processor in order to take actions to prevent damage of the DMD.
When receiving a motor command, the motor-selection and direction-signals are set and the duty-cycle of the speed-signal leaves
its zero-state. If the motor-command differs from the previous one then the overload-circuit will first be reset. An overload-signal
indicates the current-limiting status. The motor-selection-signals are also used to control the multiplexers for the encoder-signals,
so that only the position of the selected motor is considered
142
OVL
PWR
DRIVE
CHA2
CHB2
M
R5976820 SLM R12+ PERFORMER 08/03/2005
A
B
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