Lawn sensor - Versionsgeschichte

Alexanderg: /* Detailed operation */

2015-01-15T13:02:48Z

‎Detailed operation

Alexanderg: /* Principle of operation */

2015-01-15T13:02:28Z

‎Principle of operation

Frank: While technically "capacity" is a correct description of the physical effect, "capacitance" is much more common in English usage.

2015-01-06T12:33:17Z

While technically "capacity" is a correct description of the physical effect, "capacitance" is much more common in English usage.

Alexanderg: /* Wiring: */

2014-09-12T18:09:43Z

‎Wiring:

Michael: Die Seite wurde neu angelegt: „== Lawn Sensor == caption A lawn sensor should detect if the robot is still on lawn or not. In other words, it should find out if the m…“

2014-09-12T17:12:37Z

Die Seite wurde neu angelegt: „== Lawn Sensor == caption A lawn sensor should detect if the robot is still on lawn or not. In other words, it should find out if the m…“

Neue Seite

== Lawn Sensor ==

[[File:capacity.png|caption]]

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 capacity sensor can be used as the media below the robot has influence on the capacity. No difference in capacity however is between lawn and flowers etc. - so you should have a distinct area around your lawn that is different to lawn (e.g. bark mulch).

== Principle operation ==

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

<gallery>
File: l50_capmeter.jpg

File: lawn_sensor.jpg

File: capsense.gif
</gallery>

== Wiring: ==

'''''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

== Detailed operation ==

Initially, the copper plate is discharged by pulling the send pin to low.
Then 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.

@@ Zeile 8: / Zeile 8: @@
 == Principle of operation ==
-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 capacitance increases slightly (by a few pF).
+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).
 <gallery>

@@ Zeile 39: / Zeile 39: @@
 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' (capacitance measurement).
+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.

@@ Zeile 24: / Zeile 24: @@
-Arduino Mega Pin 40 Receive Front -------------|
+ Arduino Mega Pin 40 Receive Front -------------|
-Arduino Mega Pin 41 Send    Front --- 2 MOhm --+---|  Lawn
+ Arduino Mega Pin 41 Send    Front --- 2 MOhm --+---|  Lawn
 '''''Back lawn sensor:'''''
-Arduino Mega Pin 42 Receive Back  -------------|
+ Arduino Mega Pin 42 Receive Back  -------------|
-−
-Arduino Mega Pin 43 Send    Back  --- 2 MOhm --+---|  Lawn
 == Detailed operation ==