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connecting a flywheel/protection diode at the output

Created by: Vivek Kansara at: 9/24/2014 10:21 AM (6 Replies)

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9/24/2014 10:21 AM	Rate (0)
Vivek Kansara Bronze Member Joined: 9/3/2009 Last visit: 12/21/2023 Posts: 153 Rating: (12)	hello, Sub: - for s7-200, cpu 226(dc/dc/dc) , to protect the output of thePLC . while using dc output (24v dc) of the PLC, which wil actuate a relay , how can i connect the supression diode or protection diode so as to make the output safe in case reverse supply or coil is damaged. Also, should i use any MCB, or any circuit breakerfor thePLC power up ( L+ , M-). 24v dc, any help is appreciated. tnx....

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9/24/2014 10:50 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello, a "protection diode" is used for (DC) inductive loads to catch the reversed voltage that is generated when the coil is swiched off. Therefore you need to put the Diode antiparallel over the coil, see System manual page 36. There is no need to protect the CPU powerline. Ouputs should be protected by installing a fuse in the 1L+, 2L+ etc lines. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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9/24/2014 10:56 AM	Rate (0)
Vivek Kansara Bronze Member Joined: 9/3/2009 Last visit: 12/21/2023 Posts: 153 Rating: (12)	tnx marcjan. i saw the flyweel connected antiparallel to relay coil. can i also connect a protection diode directlyat the output of the PLCwhich wil actuate the relay rather connecting in antiparallel to the relay.., and which will confirms the direction of condution only in 1 direction only?? which way would be the safest.

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9/24/2014 11:34 AM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello, In my opinion it's not about safety(for your output) here, but how easy it is to connect, you can easy put a diode over a relais or actuator coil, good relais or coils have it build in or at least a optional device that you can connect easy. Regards, Marcjan
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9/26/2014 9:41 AM	Rate (0)
Vivek Kansara Bronze Member Joined: 9/3/2009 Last visit: 12/21/2023 Posts: 153 Rating: (12)	yes tnx marcjan.. though i m still little worried about the safety of plc outputs, specially transistor output (dc/dc/dc).

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9/26/2014 8:53 PM	Rate (0)
Marcjan Platinum Expert Joined: 4/22/2010 Last visit: 10/17/2024 Posts: 5697 Rating: (715)	Hello. To protect your outputs to the max, you can use optocoupler relais. But i can tell you that if you follow the manual you can't blow a output, i have not met one case of smoking output in 16 years with a 200. Regards, Marcjan
	Problem solved? Please let us know! Please no technical questions by PM, use the forum sections for your questions.
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9/28/2014 8:26 AM	Rate (0)
Vivek Kansara Bronze Member Joined: 9/3/2009 Last visit: 12/21/2023 Posts: 153 Rating: (12)	tnx marcjan... opto-coupler relays are protective as they provide safety isolation. bytheway wat do u suggest about the s7-200 (cpu226)cpu's. using a ac/dc/relay or using a dc/dc/dc ...which is the safest solution for industrial purpose. ( provided i can use ac/dc/relayor dc/dc/dc for the my application) tnx.

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