Whats a tacho and its purpose?

A tachometer, often referred to simply as a "tacho," is a crucial device for measuring and controlling the rotational speed of various mechanical systems. Here’s an in-depth look at its functions, types, applications, and significance, particularly in the context of washing machines.

Detailed Function and Purpose of a Tacho

Speed Measurement

Rotational Speed: Tachometers measure the rotational speed of an object, usually in revolutions per minute (RPM). This measurement is critical for maintaining the desired speed of the drum or motor.

Real-Time Monitoring: They provide continuous, real-time data on the current speed, enabling precise adjustments as needed.

Control and Regulation

Cycle Optimization: The tachometer ensures that the washing machine runs at optimal speeds for different cycles, such as washing, rinsing, and spinning. This helps achieve effective cleaning and water extraction.

Speed Regulation: By providing feedback to the control system, the tachometer helps regulate the motor speed, ensuring it stays within the desired range for each cycle.

Safety and Protection

Over-Speed Protection: Tachometers can detect if the motor exceeds safe speed limits and trigger safety mechanisms to prevent damage.

Load Balancing: They help in balancing the load during the spin cycle, reducing excessive vibration and noise.

Types of Tachometers

Mechanical Tachometers

Principle of Operation: These devices use mechanical components like gears and springs to measure speed.

Application: They are less common in modern washing machines but might still be found in some industrial machinery or older models.

Electronic Tachometers

Optical Sensors: Use light beams and photodetectors to measure the speed based on interruptions or reflections from a rotating object.

Magnetic Sensors: Detect changes in a magnetic field caused by the rotation of a ferromagnetic object, often using coils or Hall effect sensors.

Hall Effect Sensors: Use the Hall effect to measure the speed by detecting magnetic fields generated by the rotating object.

Applications in Washing Machines

Washing Cycle

Agitation Control: During the washing cycle, the tachometer helps maintain a consistent, moderate speed to ensure effective agitation without damaging the clothes.

Variable Speed: The speed can be adjusted based on the load type (e.g., delicate fabrics vs. heavy fabrics) to optimize cleaning performance.

Extraction (Spin) Cycle

High-Speed Spinning: In the extraction cycle, the tachometer ensures that the drum reaches high speeds necessary for efficient water extraction from clothes.

Balancing: It helps manage the drum's balance by adjusting speeds to minimize vibration and noise, especially important when dealing with uneven loads.

Importance of Speed Changes in Washing Machines

Efficiency: Low speeds during washing reduce wear and tear on clothes, while high speeds during spinning maximize water extraction.

Effectiveness: Proper speed control ensures thorough cleaning and efficient rinsing, enhancing overall washing performance.

Energy Savings: Efficient speed management reduces energy consumption, as the motor works optimally for each cycle phase.

Machine Longevity: Prevents excessive wear on the motor and other mechanical components, extending the lifespan of the washing machine.

How Tachometers Work

Basic Principle

Sensing Mechanism: Tachometers detect the rotational speed of a shaft or drum using various sensing mechanisms (optical, magnetic, Hall effect).

Signal Processing: The sensor generates a signal proportional to the rotational speed. This signal is processed by the washing machine’s control unit.

Feedback Loop: The control unit uses this feedback to adjust the motor speed, ensuring it matches the desired RPM for each cycle.

Example Calculation

Suppose a washing machine’s spin cycle is set to 1200 RPM. The tachometer continuously measures the drum’s speed. If it detects a speed deviation (e.g., drops to 1150 RPM), it signals the control unit.

Adjustment: The control unit then increases the motor power to bring the drum speed back to 1200 RPM, maintaining optimal performance.

The tachometer, also known as Tacho, is a crucial component that detects the drum's speed and transmits this information to the control unit. This unit comprises relays and a triac, which work together to adjust and control the motor's speed and overall operation effectively.

Conclusion

Tachometers are essential in modern washing machines, providing accurate speed measurements and feedback to ensure optimal performance throughout different cycles. By maintaining precise control over motor speeds, they enhance the efficiency, effectiveness, and safety of washing machines, contributing to better cleaning results and longer appliance lifespan.