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SSR Series AC Output Modules Will Not Work Properly with Boards that Have the 8255 Digital Chip

Hardware: Signal Conditioning Other>>SSR Series

Problem: My SSR series AC output modules are not turning on and off properly. I am controlling the module with a PC-DIO-24 DAQ card.

Solution: The following boards have 8255 digital chip for digital I/O:

• PC-DIO-24
  
• PC-DIO-96
  
• Lab/1200 Series,
  
• DAQCard-700
  
• PC-LPM-16
  
• PC-AO-2DC
  
• extended lines of AT-MIO-16DE-10.
  

The 8255 chip sinks a maximum of about 1.7 mA of current at the digital low state. This is not enough to drive the SSR output modules to a low state (thus turning them on).

You should use one of the following methods to get around this problem:

1. Use a non-inverting digital buffer chip between the 8255 and the SSR backplane, or
   
2. Use a DIO-32F or an MIO (e.g., E Series) board with the appropriate connections (e.g., an SC-205X and cables).
   

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Report Date: 01/11/1995
Last Updated: 05/24/2004
Document ID: 05AF71ZU

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