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BrianO

Click PLC loosing comm. connection

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I built myself a PLC trainer using a Click PLC with 2 I/O sections.It works perfect except for an issue that started when hooking up a pnuematic solenoid valve to run a small cylinder.The output section is a CO-08TR,it is energizing a small cube relay(Square D 8501,series B,120v coil).The solenoidsfor the valve are connected to the contacts of the relay,the PLC energizes the coil.When energizing the solenoids afew times,I loose my PC connection to the PLC,I leave it connected to view the ladder on screen.The trainer is fed by a single 120v household plug,feeding everything inside,including the Click power supply for the CPU.I did disconnect the solenoids,while leaving the coils connected to the PLC.This seemed to help a little ,maybe,but I would still lose my communication.I believe it has to do with voltage drop/spike ,any ideas???
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You need to add some sort of CEMF protection to the Solenoid. Either a diode (1n4004 or similar), varistor, etc to reduce the "kickback" when the solenoid de-energizes. See the Click Hardware manual Page 3-30. I know it says for Relay Outputs, but it is required for any output. Edited by rlp122
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Obviously since they are AC coils a varistor for each would be more in order. I really like your trainer. Good work.
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Quite correct. I missed that tidbit when I read the post the first time.

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