STEPRACE: Service & Maintenance Manual - rev. 1.2
Page 3.5
alternator speed signal as a feedback signal, the CPU board adjusts the excitation PWM signal
so as to maintain a constant speed (closed loop control).
•
mode B
: In this stepping mode, the user can choose between 3 different resistance levels
(WEAK, MEDIUM and STRONG), while the difficulty level setting determines the target speed
to be maintained. In this case, the CPU board sets one of 3 different values for the PWM
excitation signal as a function of the selected resistance level, independently of the selected
difficulty level (open loop control).
3.2.3. T
HE CONTROL SIGNALS
The machine controls the difficulty level of the workout by means of the CPU board, the alternator
interface board and the alternator, as illustrated in the figure below:
The following signals are involved in the control loop:
•
Microswitch signal
This is the microswitch contact which detects the position of the selection knob and hence the
chosen stepping mode. The contact is closed if the selection knob is released in the “out”
position, and open if the knob is pushed in.
This signal reaches the alternator interface board (pin 5-6 of connector CN2) and is logic level
high (5 Vdc) if the knob is pushed in, and logic level low (0 Vdc) if the selection knob is
released. The signal is output (pin 8-3 of connector CN1) to the CPU board (pin 8-3 of
connector CN1).
CPU board
Alternator interface
board
RPM
PWM
micro
8-3
6-3
5-3
CN1
8-3
6-3
5-3
CN1
5-6
4-5
1-5
CN2
Alternator
RPM
Microswitch
PWM
Resistor
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