Speed Sensor Troubleshooting - Precor Precision 400 Series Service Manual

Speed Sensor Troubleshooting

Troubleshooting the Speed Sensor system.
Note: The speed sensor is an IR transmitter/receiver through sensor. The signal to
the processor is pulsed by a chopper wheel with crenellations that break the signal
in the sensor as the motor rotates. The signals are 5VDC pulses, and give the pro-
cessor the indication that there is motor movement, and the rate of speed. These
pulses are used by the processor to vary the drive to the motor, thus controlling the
speed. The sensor is attached to the drive motor via a mounting plate secured by a
single hex head screw.
If the sensor needs to be replaced it is recommended that the chopper wheel be removed
from the motor shaft, thus allowing easier access to the sensor mounting screw. The chop-
per wheel is secured by a single Phillips head screw.
Initial speed sensor voltage mesurements: Set the treadmill circuit breaker in the "ON" pos-
1
ition. Using a DC voltmeter, measure the speed sensor voltage between terminal 3 of J3
(white wire) and terminal 4 of J3 (black wire) on the
flywheel. The voltage should read approximately 0.25 Vdc when a lobe is between the
speed sensor "legs" and approximately 5 Vdc when a lobe is not between the speed sensor
"legs".
1
Direct Current: electrical current that only flows in one direction.
2
Lower Printed Circuit Assembly board; also refered to as the Lower PCA or simply as the
lower board. On treadmills, it is the console to base function interface and the motor con-
troller unit (MCU). On self-powered units, it is the lower PCA console to base function inter-
face.
Contact Precor Customer Support at support@precor.com or 800.786.8404 with
any questions.
System Troubleshooting Procedures
2
LPCA . Slowly, rotate the drive motor
7 Troubleshooting
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