Knowledge Extension of Digital Pir Obstacle Avoidance Sensor

Knowledge Extension of Digital Pir Obstacle Avoidance Sensor

Digital pir obstacle avoidance sensor is a photosensitive sensor which integrates transmission and reception. The emitted light is modulated and sent out. The receiver demodulates the reflected light. The interference of visible light is effectively avoided. The use of lenses also allows the sensor to detect up to 80 cm distances (due to the characteristics of infrared light, objects of different colors can detect different maximum distances; white objects are farthest, and the black objects are nearest).


The distance of the obstacle can be adjusted by the potentiometer knob at the tail according to the requirement. The sensor has the characteristics of long detection distance, less visible light interference, low price, easy assembly and easy use, which can be widely used in obstacle avoidance of robots, pipeline parts and other occasions.


Knowledge Development of Digital Pir Obstacle Avoidance Sensor


Pull-up Resistance and Pull-down Resistance


In digital logic circuits, a signal is either 0 or 1. Because of this, the design of digital circuit is simple and reliable. Usually, Voltage 5V (or close to 5V) is used to represent on open state, high level and corresponding state is state 1. Voltage 0V (or close to 0v) is used to represent off state, low level and corresponding state is state 0. Some development boards are based on 3,3V, so 3.3V is used as a high level. If the voltage in a circuit is in an uncertain state (e.g. when a pin is not connected to any other circuit), we will say that its voltage is floating, and it will change and jump with time, and it is easily affected by the external environment. Circuits in this uncertain state are randomly interpreted as high or low levels. This phenomenon is also called electronic noise. However, the program must be rigorous and accurate, so the circuit design must avoid a floating state for the line voltage. We can use pull-up resistance or pull-down resistance to keep the voltage of the circuit in a certain state at any time, which is the role of pull-up resistance and pull-down resistance.


Pull-down resistance: Pull an unknown level down to a stable low-level state.


Pull-up resistance: Pull an unknown level up to a stable high-level state.

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