Infrared motion detection

In this example we are going to connect to infrared motion detection sensor.

We will be using HC-SR501 sensor which is a very common type. (At bottom of the Guide we also test unknown Infrared sensor and ST-00082 Mini)

Back side of my sensor was like this:

Where I put H & L there is usually a jumper to be able to configure it as either H (Repeat trigger mode) or L (Single trigger mode). This one I have right now has no jumper and if peering eyes on the board then it seems to be permanently set to H (Repeat trigger mode).

Sensitivity adjusts the trigger range. (Turn clockwise to increase range)

Time delay adjustment is for adjusting the detection delay (0.3 seconds to 600 seconds): Turn the potentiometer clockwise to increase delay.

Pieces we use:

• Raspberry Pi 2, 3, 4 or 5.
• Cobbler and Cobbler cable.
• Breadbboard.
• HC-SR501 sensor.
• 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.

First thing is connecting the sensor:

Make sure that your Raspberry PI is not turned on when your wiring it up. 

Wiring of the HC-SR501 - (This is older picture from last time I did this, notice this one does actually have the jumper which the one I have now does not have)

Note that when shown on the breadboard the sensor is shown from the other side, so check the picture above to make sure the wires go in right place.

• (Sensor VCC to 5 V on Raspberry Pi) -  I always use red for the power input.
• (Sensor OUT to GPIO5 on Raspberry Pi) - I used the yellow wire here.
• (Sensor GND to GND on Raspberry Pi) - I used blue for the ground wire.

(Inspect your sensor carefully for markings, I have seen sensor of this type that had the pins in different order, the sensor I used last time had no markings on it so I just had to know the pin order, if you have such case then you can use the picture a bit above to go by).

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, "watch-line-value")
    
    lineRequest.RequestReadEdgeEventsAsync(10, 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.RISING
  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

After this I proceeded to test another Infrared sensor I had.

For this one I had no name at all for. So no specifications at all.

Warning do not connect this one directly to the GPIO pin.
Not knowing its specs then I had to measure it up with voltage meter and I found that the out pin was putting out 4.4V which is enough to damage your Raspberry Pi.

One more sensor is  ST-00082 Mini.

This one is drop in replacement for the HC-SR501 sensor.

Summarize for the different sensors:

Same code example works for all three sensors, but special care is needed when wiring the unknown sensor.