SW520D Tilt sensor

In this example we are going to connect the Raspberry Pi or alternate board to tilt sensor. A tilt sensor is also sometimes called angle sensor.

This example is very easy and can run on same code as our vibration sensor example.

SW520D tilt sensor

Pieces we use:

• Raspberry Pi 2, 3, 4 or 5.
• Cobbler and Cobbler cable.
• Breadbboard.
• SW520D tilt sensor on brake-out board.
• Gpiod Plugin for Xojo to use libpgiod in Xojo. The plugin you can get download here.  Or if you are interested in its source code then you can go here.

How this sensor works:

This sensor is basically a mechanical switch with metal balls inside. When the housing gets tilted the balls will close the circuit as shown on the picture above.

(Note that the signal on the brake-out board we use is reversed from what you might think from how the mechanical switch works, so the board will return Digital LOW when the switch is ON and Digital HIGH when the switch is Off.

Variations:

Different styles of SW520D

The sensor it self can come in different housings, some of whic hcan easily be confused with a capacitor.

The bakeout boards exist with one or two sensors on them, when there are two then you get two digital output channels.

Wiring:

• VCC  we connect to (3.3V) .
• DO digital output which we connect to GPIO 5 pin.
• GND we connect to ground on the Raspberry Pi.

If you have two channel sensor board and wish to use both channels then wired up the 2nd digital output to other GPIO pin.

The potentiometer on the board allows you to adjust the sensitivity of the DO output. 

The board has PWR_LED and a DO_LED. 

The sensor will have the PWR_LED showing that it is turned on.

The DO_LED lights up when the circuit it closed. (Sensor is standing upwards).

The sensor puts out digital HIGH when circuit is not closed, and digital LOW when circuit is closed.

Spec on this sensor is:

• The working voltage of 3.3V to 5V
• Output form: digital switch output (0 and 1) . (When I measured this then the output will have same voltage as the Input given to the sensor)
• Sensitivity adjustable digital potentiometer to adjust.
• Product no vibration, vibration switch is closed on state, the output terminal output low level, the green light is lit.
• Product vibration, the vibration switch instantaneous disconnection, output the output high level, the green light is not bright.

Note the picture is showing a vibration sensor since I did not have Fritzing part for the SW520D, but their wiring is 100% the same.

Raspberry Pi pin layout

The Xojo Code

Private mLineRequest As Gpiod.LineRequest

And then Opening event for the Window:

Sub Opening() Handles Opening
  try
    using Gpiod
    
    var chip as Chip = Chip.Open("/dev/gpiochip0")
    
    var lineRequest as LineRequest = RequestInputLine(chip, 5, "tilt-sensor")
    
    lineRequest.RequestReadEdgeEventsAsync(5, true, AddressOf LineMonitorCallback)
    
  catch e as GpiodException
    MessageBox(e.Message)
  end try
End Sub

Helper function to set up the line

Public Function RequestInputLine(chipHandle as Gpiod.Chip, lineOffset as UInt32, consumer as String) As Gpiod.LineRequest
  using Gpiod
  
  // Exceptions will be caught by the caller method
  
  var reqCfg as RequestConfig = nil
  
  var setting as new LineSetting()
  setting.Direction = Gpiod.Direction.INPUT
  setting.EdgeDetection = Gpiod.LineEdge.FALLING
  setting.Bias = Gpiod.LineBias.PULL_DOWN
  
  var lineCfg as new LineConfig()
  lineCfg.AddLineSetting(array(lineOffset),setting)
  
  if consumer <> "" then
    reqCfg = new RequestConfig()
    reqCfg.Consumer = consumer
  end if
  
  return chipHandle.RequestLines(reqCfg, lineCfg)
End Function

Callback for our events:

Public Sub LineMonitorCallback(edgeEvent as Gpiod.EdgeEvent)
  lstEvents.AddRow(if(edgeEvent.EventType = Gpiod.EdgeEventType.RISING_EDGE, "Rising", "Falling"))
  lstEvents.CellTextAt(lstEvents.LastRowIndex, 1) = edgeEvent.LineOffset.ToString()
  lstEvents.CellTextAt(lstEvents.LastRowIndex, 2) = edgeEvent.LineSequenceNumber.ToString
  lstEvents.CellTextAt(lstEvents.LastRowIndex, 3) = edgeEvent.TimestampNs.ToString()
End Sub