Frequency. The sensor produces a signal in which the frequency (Hz) varies as the condition changes.
Pulse Width Modulated (PWM). The sensor produces a signal in which the duty cycle varies as the condition changes. The frequency of the signal is constant.
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| Illustration 1 | g01106957 |
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Speed dial and buffer | |
The speed dial is an input to the ECM. The purpose of the dial is to allow the machine operator to control the maximum speed of the machine. The position of this dial will determine the maximum speed of the machine. The machine will propel at maximum speed under the following conditions.
- the speed lever is all the way forward
- the brake pedal is all the way up
- the steering wheel is centered
- the engine is at high idle
The speed dial is a potentiometer that produces a 0 - 5 volt signal as the dial is rotated from minimum position to maximum position. This voltage is converted by the buffer to a PWM signal that is sent to the ECM. This PWM signal will always have the same frequency (5000 Hz), however, the duty cycle of the signal is proportional to the dial position. When the speed dial is rotated from the minimum position to maximum position, the duty cycle of the PWM signal will vary from 5 percent to 95 percent.
The signal for the speed dial connects to ECM connector contact 3.
The Speed Lever is an input to the ECM. The purpose of the lever is to allow the machine operator to control the speed and direction of the machine. The position of this lever determines whether the machine is in neutral (center position), forward, or reverse. The position of the lever within the forward or reverse range will determine how fast the machine will propel. The farther the lever is from the neutral position, the faster the machine will propel.
The speed lever is a potentiometer that produces a 0 - 5 volt signal as the lever is moved from maximum reverse position to maximum forward position. This voltage is converted by the buffer to a PWM signal that is sent to the ECM. This PWM signal will always have the same frequency (5000 Hz), however, the duty cycle of the signal is proportional to the lever position. When the speed lever is moved from maximum reverse position to maximum forward position the duty cycle of the PWM signal will vary from 15 percent to 85 percent.
The signal for the speed lever connects to ECM connector contact 27.
Steering Sensor - (For Tracked Pavers)
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| Illustration 2 | g01106979 |
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Steering sensor | |
The steering sensor is an input to the ECM. The purpose of the steering sensor is to monitor the selected turning radius of the machine. The operator turns the steering wheel and the position of the wheel determines the selected turning radius of the machine. The ECM calculates what the speed of the tracks should be in order to achieve this turning radius. The ECM will then maintain the tracks at the selected speed. A single PWM input at the ECM monitors the steering wheel position.
The steering sensor generates a PWM signal. The PWM signal will always have the same frequency (5000 Hz), however, the duty cycle of the signal is proportional to the steering wheel position. As the steering wheel is rotated from the counter-clockwise stop to the clockwise stop, the duty cycle of the PWM signal will vary from 15 percent to 85 percent.
The signal for the steering sensor connects to ECM connector contact 4.
Steering Sensor - (For Wheeled Pavers)
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| Illustration 3 | g01106986 |
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Steering wheel sensor | |
The steering sensor is an input to the ECM. The purpose of the steering sensor is to monitor the desired turning radius of the machine. The operator turns the steering wheel and the angle of the front wheels of the paver determines the desired turning radius of the machine. The ECM calculates what the speeds of the wheels should be to achieve this turning radius. The ECM will then maintain the wheels at those speeds. A single PWM input at the ECM monitors the steering angle position.
The steering sensor generates a PWM signal. This signal will always have the same frequency (5000 Hz), however, the duty cycle of the signal is proportional to the steering angle. As the front wheels are rotated from full left to full right, the duty cycle of the PWM signal will vary from 15 percent to 85 percent.
The signal for the steering sensor connects to ECM contact 4.
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| Illustration 4 | g01106990 |
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Brake pedal sensor | |
The brake pedal sensor is an input to the ECM. The purpose of the brake pedal sensor is to monitor the selected speed of the machine. The operator depresses the brake pedal in order to lower the speed of the machine. Braking action is not applied until the brake pedal is fully depressed, however, the ECM slows the machine by supplying less output current to the propel pump solenoids. A single PWM input at the ECM monitors the brake pedal position.
The brake pedal sensor generates a PWM signal. This signal will always have the same frequency (5000 Hz), however, the duty cycle of the signal is proportional to the brake pedal position. As the brake pedal is moved from fully depressed position to fully up position, the duty cycle of the PWM signal will vary from 25 percent to 65 percent.
The signal for the brake pedal sensor connects to ECM contact 28.
Left Speed Sensor / Right Speed Sensor
The speed sensors are inputs of the ECM. The purpose of the sensors is to tell the ECM the speed of each track or wheel. The ECM uses this information in order to control the speed of the tracks or wheels depending on the selected speed. The speed sensors are Hall Effect sensors. The sensor receives approximately 10 DCV from the ECM. As a gear tooth passes the Hall cell, a change in the magnetic field produces a small signal. The internal electronics of the sensor processes the signal and sends a digital signal to the ECM. The ECM measures the frequency of the signal and the ECM responds accordingly to the signal.
The signal for the left speed sensor connects to ECM contact 6. The signal for the right speed sensor connects to ECM contact 7.
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| Illustration 5 | g01106992 |
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Engine speed sensor | |
The purpose of the sensor is to tell the ECM the speed of the engine. The ECM uses this information in order to control the selected speed of the tracks or the wheels. The ECM also uses this information in order to determine the status of the engine (on, off, cranking). This speed sensor is a frequency sensor. Frequency sensors produce a signal which varies the frequency (Hz) as the condition changes. The sensor generates a sine wave signal from passing gear teeth, which is sent to the ECM. The speed sensor has a plus (+) and a minus (-) connection to the ECM. The ECM measures the signal frequency as one pulse per tooth and determines the engine speed.
The signal for the engine speed sensor connects to ECM connector contact 5.