Lawn sensor ru

Датчик травы

A lawn sensor should detect if the robot is still on lawn or not. In other words, it should find out if the media directly below the robot is still lawn or something else (air etc.). Therefore, a capacitance sensor can be used as the media below the robot has influence on the capacitance. However, there is no difference in capacitance between lawn and flowers etc. - so you should have a distinct area around your lawn that is different to lawn (e.g. bark mulch).

Датчик травы должен обнаружить, находится ли робот все еще на лужайке или нет. Другими словами, он должен узнать, есть непосредственно под роботом газон или же что-то еще (воздух и т.д.). Емкостной датчик может быть использован в качестве датчика.

Нет никакой разницы в емкости между травой и полезными цветами, которые посадила ваша жена, грядками клубники и т.д. - так что вы должны иметь четкую зону вокруг вашего газона (например, мульчу).

Принцип работы

A lawn sensor could be a copper plate in a closed plastic tube. To find out if the plate has contact with lawn, the capacitance of this sensor is measured. If the robot is on lawn (lawn is 'dielectric'), the measured capacity increases slightly (by a few pF).

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Подключение

Front lawn sensor:

Arduino Mega Pin 40 Receive Front -------------| 

Arduino Mega Pin 41 Send    Front --- 2 MOhm --+---|  Lawn 

Back lawn sensor:

Arduino Mega Pin 42 Receive Back  -------------| 

Arduino Mega Pin 43 Send    Back  --- 2 MOhm --+---|  Lawn

Детали операции

Initially, the copper plate is discharged by pulling the send pin to low. Then the send pin is set to 'high' - via a resistor (2 Megaohm) the copper plate is charging slowly. By constantly reading input receiver pin, the Arduino measures the time until it becomes 'high' (capacity measurement). Because microcontrollers are fast and precise in time measurement, you can measure very low capacities with this.