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Hi guys,

I am trying to connect a reed contact to a SDM-IO 16 for checking if a window is closed or not.

This is the code I am using to test the reed contact. A slightly changed version of the example in the SDM-IO 16 manual.

'CR6 Series Datalogger
'To create a different opening program template, type in new
'instructions and select Template | Save as Default Template
'date:
'program author:

Public Version(4)
Public ComsStat(3)
Public flag(16)
Public Setup(1)
Alias version(1)=OS_Ver
Alias version(2)=OS_Sig
Alias Version(3)=WatchDog
Alias Version(4)=ComErr
Public window_open As Boolean

BeginProg
window_open = FALSE

'Set up the SDM-IO16.
  Scan(1,sec,0,2)      
     'Set IO ports 1-16 to input switch closure.
      SDMIO16(Setup,ComsStat(1),0,90,2222,3333,0000,0001,1,0)             
  NextScan  
    
'Measure.
 Scan(1,sec,0,0)      
  ''WINDOW OPEN COMMAND
    If window_open = TRUE Then
       SDMIO16(Version,ComsStat(2),0,90,9999,9999,9999,9919,1,0)
    Else
       SDMIO16(Version,ComsStat(2),0,90,9999,9999,9999,9909,1,0)
    EndIf 
           
  ''CHECK PORTS
       SDMIO16(flag(),ComsStat(3),0,92,0,0,0,0,1,0)
     ' SDMIO16(flag(),ComsStat(3),0,14,0,0,0,0,1,0)               
 NextScan      
EndProg

I can change the value of flag(2) if I set window_open to true (that’s what I need to access the relay which opens the window), but I am not able to connect this reed relay the right way and read the value I need for a logger controlled automatic mode.

What I tried is to connect the source wire to 5V and the normally open wire from the reed relay switch to one of the control ports of the SDM-IO 16. When I put a magnet near the relay it closed the switch, but I was not able to receive any signal.

I tried to set up several ports with modes from 2 to 5, no result.

All I get is 5V between every port which is not set to “Output logic low (0)” and ground.

Is it possible to drive a reed relay from one port (5v out/logic high) and measure the signal with another port (5v in/logic low) of the SDM-IO 16?

Thank you in advance,

Best regards

The channels on the IO16 have 100kOhm internal pullup resistors.(channels default high) Use the channel and ground for the two leads to the switches. The channels will go low when the switch closes.

Thank you very much. I overlooked this pullup resistor again and again.

Now it works perfectly.