jonala Posted January 14, 2005 Report Posted January 14, 2005 How can I make a solid state relay (OPTO-22, G4ODC5) turn off when connected to a plc input? The LED on the relay shows that it is off but the plc input shows that it is on. Quote
guillencito Posted January 17, 2005 Report Posted January 17, 2005 Maybe you have a wrong polarization for the PLC input. Check if it is PNP or NPN, and if it match the Opto22 polarization. Regards! Quote
panic mode Posted January 17, 2005 Report Posted January 17, 2005 I would check leakage current when relay is off. PLCs are very sensitive and can see mA or two as on signal. If this is the case you can add additional load in parallel with the input to 'sink' the leakage current. Quote
jonala Posted January 17, 2005 Author Report Posted January 17, 2005 J.Guillén, I'm switching a O vdc signal, there is no polarity. Panic Mode, What size resistor? The OPTO -22 relay has a rated 1 mA of leakage. My backup plan is to go with Continetal Ind. SSR I.O-ODC-RL-060 which has 100 microA leakage. The reason I don't go with a regular relay is the process is running at 10Hz. Thanks for your help. Quote
Snerkel Posted January 18, 2005 Report Posted January 18, 2005 To get a current flow into the input you must have a potential difference, even switching a 0v line has a polarity. If the voltage being switched is 24v then a 2k7 0.25W resistor across the input will do. Quote
BobB Posted January 18, 2005 Report Posted January 18, 2005 Usually better to use a transistor. Quote
jonala Posted January 18, 2005 Author Report Posted January 18, 2005 Got it working! The 2.7K resistor and swapping the wires did the trick. Thanks again Quote
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.