Precor GEN06 Series C952 Service Manual page 114

8 Theory of Operation
Treadmill Base Operation
In order to turn the motor in forward and reverse directions, the AC motor has 2 separate wind-
ings, one for up and one for down direction. The AC-1 input has a continuous connection to
the center / common connection of the motor winding.
The system has a 2A fuse to protect the components from over-current failure.
When a control signal is applied to the "UP" input, TRIAC-1 control line is active and turns on
the up triac. This directs the AC-2 connection to the up winding of the motor, causing the motor
to spin in the up direction.
When a control signal is applied to the "DOWN" input, TRIAC-2 control line is active, turns on
the down triac. This directs the AC2 connection to the down winding of the motor, causing the
motor to spin in the down direction.
Since the lift motor runs directly on the AC input voltage, it is important to note that there is a dif-
ferent part number for a 120 Vac unit and a 240 Vac unit.
Position Monitoring
The unit also requires an absolute measurement of lift position. This is achieved through the
use of a potentiometer. The potentiometer resistance wiper is turned by gears in the lift motor.
With +3. 3 Vdc is applied across the potentiometer, the center wiper connection will create a
variable voltage between 0 and +3. 3 Vdc representing the position of the lift or incline. This
variable voltage is applied to the input of a 16-bit A/D converter which converts the analog
voltage into a 16-bit binary numeric representation that the processor can understand.
As the potentiometer voltage changes between 0 and 3. 3 Vdc, the corresponding A/D values
change between 0 and 65507. The processor uses the A/D number to track the lift position.
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