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10
4 Detailed Operations
4.1 Motor Speed Control
The SE3001 adjusts the chopping frequency by changing the motor voltage in internal reference mode and external
reference mode. The rated motor voltage range is from 0V to 12V. When the motor voltage direction is proper, the
motor will run at a frequency associated with the motor voltage amplitude.
The control module in the SE3001 control box reads the set frequency and sends the corresponding control signal
to the ADC module. A proper voltage at the output of the ADC module will be amplified and regulated, and finally
acts as the motor voltage to control the motor speed. The larger the motor voltage, the higher the motor speed.
4.2 Frequency Measurement
The SE3001 uses two photoelectric doors to detect the spinning speed of the blade. Each photoelectric door has a
linear light source and a photoresist. When the blade blocks the light from the linear light source, the photoelectric
door outputs a high voltage due to a high resistance of the blocked photoresistor. On the contrast, when the
photoresist receives the light from the light source, the photoelectric door outputs a low voltage due to a low
resistance of the unblocked photoresistor. When the blade spins steadily, the output voltage is like the figure below:
The output frequency of the photoelectric door is the spinning frequency of the blade. After a schmidt trigger and a
phase inverter, the output voltage of the photoelectric door as a feedback signal is sent to the SE3001 control box.
The SE3001 control box uses two timers T1 and T2 to measure the frequency of the feedback signal. The T1 timer
is triggered by the rising or falling edge of the signal. The T2 is triggered by a standard periodic pulse signal. When
the T1 is triggered by the first edge of the signal at the first time, the T2 starts counting time. The T1 and T2 timers
will stop at the same time when the T1 counts up to n. Assuming the T2 gets a certain time length T during the
whole counting time, the period of the feedback signal is defined as T/n. Therefore, the frequency is n/T.
4.3 Frequency Adjustment
The SE3001 adjusts the spinning frequency of the blade by changing the motor spinning frequency roughly and
then subtly.
Every time using a new type of blade, users must choose a proper type of blade at
“
Blade
”
menu. Then, the
SE3001 will automatically use a motor frequency-voltage formula which is associated with the certain type of the
used blade, and get a proper motor voltage according to the set frequency and the formula. Although the rough
