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Part 4, the Final Episode of “A Brief History and Evolution of Automotive Transmissive Sensors”

The Fully Evolved TCUT1800X01

The TCUT1800X01 is a 4-channel transmissive sensor designed for incremental and absolute encoder applications. The sensor combines two infrared emitters with four detector channels in a small, 5.5 x 5.85 x 7mm surface mount package. In combination with an application specific code wheel or strip, the sensor is ideally suited for a wide range of applications such as rotary switches, incremental turn switches, and speed and motion TCUT1800X01 (4 emitters)control systems. The integration of four channels into the automotive-qualified package also makes this sensor an excellent choice for more complex applications such as automotive steering wheel encoding, where multiple channels or channel redundancy is required.

historyDepending on the application, the sensor can work as an absolute encoder or incremental encoder. The difference between both operating modes is shown in Figure 1. Used as an absolute encoder, the TCUT1800X01 provides up to 16 different binary states. The application can decode this binary code and can directly translate this information to know at which of the 16 different positions the object is located.

A typical example for this could be climate control knobs in a car. The 16 positions can be used to turn on the air conditioning or heater, and select for up 16 levels of airflow. The 16 positions could be used to not only select temperature but blower speed at different combinations of air vent locations.

For applications requiring more than 16 stages, incremental encoding could be the solution. Unlike absolute encoding, incremental encoding does not provide an exact position. It can provide the relative distance the code wheel or strip moved and in which direction.

This information can be processed by a microcontroller counting up or down to virtually generate an unlimited number of stages.

The incremental encoder example shows transitions that occur every 45° of rotation. This is twice the resolution of dual channel sensors which have only 90° phase shift information. The sensor can also be used as a fail-safe in safety related applications. For example, Ch1 and Ch2 have a phase shift of 90° while Ch3 and Ch4 are used to sense the same phase shift. The sensor could be used in applications where two channels are used for incremental encoding and two channels are used for absolute encoding.

binary_diagram

incremental_diagram

Samples are available for all the sensors mentioned in this article. The TCUT1600X01 will be introduced in November while the TCUT1630X01 and TCUT1800X01 will be released in January.

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This entry was posted on November 11, 2015 by in Articles, Infrared Emitter, Photo Detectors.
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