Understanding Tilt Sensors: Types, Working Principle, and Applications

Tilt sensors are essential for detecting angular movement, inclination, or orientation in many devices and systems. From smartphones to robotics and automotive applications, these sensors play a crucial role in maintaining balance, stability, and proper functionality. This article explores the different types of tilt sensors, explains their working principles, and highlights the diverse applications they support across industries.

What is a Tilt Sensor?

• A tilt sensor is an electronic device that measures the degree of tilt or inclination.
• There are two main types: mercury tilt sensors and ball-based tilt sensors. Here, we will focus on the ball-type tilt sensor.
• Tilt sensors are used in various applications, most commonly in smartphones and digital cameras to automatically adjust the screen display when the device is rotated.

• Figure 1 shows a breakout board with a tilt sensor from Parallax Inc.
• It uses steel balls to either make electrical contacts or to block an IR LED.
• As shown in Figure 2, the tilt sensor contains a square cavity in which a rolling ball sensor is used.
• At one corner of the cavity is a red LED, while two phototransistors, labeled ‘A’ and ‘B’, are placed at the corners on the left and right.

Tilt Sensor Working Principle

Let’s dive into how a tilt sensor actually works.

• Figure 2 depicts a 4-directional tilt sensor or tilt switch.
• It consists of one IR LED, two photo-transistors, and a small ball that moves when the tilt sensor is rotated.

Here’s how the sensor behaves in different positions:

• Location A: Phototransistor 1 is OFF, Phototransistor 2 is OFF. The ball blocks the light emitted by the LED.
• Location B: Phototransistor 1 is ON, Phototransistor 2 is OFF. The ball blocks phototransistor 2.
• Location C: Phototransistor 1 is ON, Phototransistor 2 is ON. The ball doesn’t block either port.
• Location D: Phototransistor 1 is OFF, Phototransistor 2 is ON. The ball blocks phototransistor 1.

This type of tilt sensor can be used to determine four distinct positions based on its rotation around a single horizontal axis.

Tilt Sensor Applications

Here are some uses of tilt sensors:

• Tilt sensing for remote controls
• Rotating display adjustment in smartphones and tablets
• Robotic movement
• Alarm systems
• Light switches containing mercury switches
• Indicating the orientation of consumer electronic devices such as digital cameras
• Used in aircraft to indicate the position of the aircraft with respect to the Earth during landing, takeoff, and flight
• Used to stop an electric fuel pump if a motorcycle falls on its side
• Four tilt switches are used in a game controller with a joystick

Tilt Sensor Types

Here are some types of tilt sensors based on their construction and working principles:

• Single axis, single output: The sensor responds to being tilted around one horizontal axis, relative to the downward force of gravity.
• Dual axis, dual output: The sensor contains two sensing elements at 90 degrees to each other. Each has an output determined by its angle of tilt from vertical around one axis.
• Dual axis, single output: A single sensor responds to an angle of tilt from vertical around any horizontal axis.

Mercury Tilt Sensor

• These are older tilt switches that use a blob of mercury in a glass tube.
• When the bulb is tilted, mercury rolls to the end and makes an electrical connection between two metal contacts penetrated inside the bulb for this purpose.
• Advantages: Mercury is an excellent electrical conductor and offers a long operating life, usually 100 years.
• Disadvantages: Mercury is a hazardous substance to the environment; therefore, its use is restricted.

Ball-Based Tilt Sensor

• It’s the most common type of tilt sensor or tilt switch.
• It consists of a cylindrical metal or plastic enclosure containing two spherical steel balls, which may be nickel-plated or gold-plated.
• When the switch is tilted, the balls eventually move downward. The lower ball makes an electrical connection between the two contacts or with a single contact & metal enclosure. The second ball is included to add weight and suppress vibration in the first.
• Surface mount tilt sensors are available with 2 axes. It contains one IR LED, two phototransistors, and a small ball that moves when the sensor is rotated.

Other Types of Tilt Sensors

• Force balance sensors
• Electrolytic tilt sensors
• Solid-state sensors
• Capacitive tilt sensors
• Accelerometers

Conclusion

Tilt sensors are invaluable for industries that require accurate detection of angle and orientation. Understanding the different types of tilt sensors, how they work, and their applications can help in selecting the right sensor for specific needs. As technology advances, tilt sensors will continue to evolve, enhancing safety, precision, and functionality across an expanding range of applications.