Reed switch
In this example we are going to connect the Raspberry Pi or alternate board to Reed switch.
Reed switches are a special kind of electrical switch, actuated (turned on and off or change over) by magnetism.
I will be using KY-021 brake-out board. Though it is such a simple board that you can as well use just Reed switch. Only components on the board are the Reed switch and a 10kΩ resistor.
A Reed switch is sort of like hall sensor where the difference is that Reed switch consumes no power at all while idling and waiting for magnet to turn things on while hall sensor consumes power all the time. But hall sensor is not mechanical and can therefor measure much faster making it good for all sorts of time sensitive measures.
Reed switch on KY-021 brake-out board
DISCLAIMER
We do not take any responsibility for possible errors in the guide or errors that you might do wiring it up. Incorrect wiring can result in damaged sensor or damaged Raspberry Pi.
Pieces we use:
- Raspberry Pi 2, 3, 4 or 5.
- Cobbler and Cobbler cable.
- Breadbboard.
- Reed switch on KY-021 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:
When there is no magnetic field near the sensor then the output will put out HIGH, while if there is magnetic field near the sensor then the output will output LOW. (You can test with magnet).
Wiring:
- + (middle pin) we connect to (3.3V) .
- S (left pin) output pin which we connect to GPIO 5 pin.
- - (pin on rightside) we connect to ground on the Raspberry Pi.
Warning
This sensor is just a switch so what you put in comes out. We have to connect this to the 3.3V on the Raspberry Pi and not the 5.5V, else the output can damage the Raspberry Pi pin.
Spec on this brake-out board sensor is:
- The working voltage of 3V to 5V
- Output signal: HIGH when no magnetic field, low when in magnetic field.
If you are not familiar with working with a breadboard or on how to place a cobbler on the breadboard then click here bellow
Breadboard
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 layoutIf you need more information about the GPIO headers on Raspberry Pi or other boards then click bellow.
Raspberry Pi Pin guideOrange Pi One Pin guideOrange Pi Pin guide for most H3 modelsOrange Pi Zero 3 Pin guideOrange Pi 5 Plus Pin guideRock 64 Pin guideRaspberry 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, "reed-switch")
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.DebouncePeriod = 10000
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
Getting the code
You can find this example code at Example code for GPIO guides.
Reed switch
In this example we are going to connect the Raspberry Pi or alternate board to Reed switch.
Reed switches are a special kind of electrical switch, actuated (turned on and off or change over) by magnetism.
I will be using KY-021 brake-out board. Though it is such a simple board that you can as well use just Reed switch. Only components on the board are the Reed switch and a 10kΩ resistor.
A Reed switch is sort of like hall sensor where the difference is that Reed switch consumes no power at all while idling and waiting for magnet to turn things on while hall sensor consumes power all the time. But hall sensor is not mechanical and can therefor measure much faster making it good for all sorts of time sensitive measures.
Reed switch on KY-021 brake-out board
DISCLAIMER
We do not take any responsibility for possible errors in the guide or errors that you might do wiring it up. Incorrect wiring can result in damaged sensor or damaged Raspberry Pi.
Pieces we use:
- Raspberry Pi 2, 3, 4 or 5.
- Cobbler and Cobbler cable.
- Breadbboard.
- Reed switch on KY-021 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:
When there is no magnetic field near the sensor then the output will put out HIGH, while if there is magnetic field near the sensor then the output will output LOW. (You can test with magnet).
Wiring:
- + (middle pin) we connect to (3.3V) .
- S (left pin) output pin which we connect to GPIO 5 pin.
- - (pin on rightside) we connect to ground on the Raspberry Pi.
Warning
This sensor is just a switch so what you put in comes out. We have to connect this to the 3.3V on the Raspberry Pi and not the 5.5V, else the output can damage the Raspberry Pi pin.
Spec on this brake-out board sensor is:
- The working voltage of 3V to 5V
- Output signal: HIGH when no magnetic field, low when in magnetic field.
If you are not familiar with working with a breadboard or on how to place a cobbler on the breadboard then click here bellow
BreadboardNote 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 layoutIf you need more information about the GPIO headers on Raspberry Pi or other boards then click bellow.
Raspberry Pi Pin guideOrange Pi One Pin guideOrange Pi Pin guide for most H3 modelsOrange Pi Zero 3 Pin guideOrange Pi 5 Plus Pin guideRock 64 Pin guideRaspberry 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, "reed-switch")
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.DebouncePeriod = 10000
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
Getting the code
You can find this example code at Example code for GPIO guides.