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Author Topic: Do I need a fly back diode for a relay controlled solenoid  (Read 836 times)
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I've been reading through the forum and I understand that I need a fly back diode when driving an inductive load due to back emf.  The 12VDC 6A solenoid is controlled through the relay that is connected to the arduino.   The relay circuit has a fly back doide, but do I also need one for the solenoid that's the separate circuit?

thanks,

John
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I don't think you connected the grounds, Dave.
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You don't need one, but it might make your relay contacts last a little longer.
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There have been a few posts here where folks have switched a solenoid with a relay without a flyback diode across the solenoid, and the Arduino has tended to lock up or suffer other problems when the solenoid was switched. In at least one case, adding a flyback diode fixed the problem So a flyback diode is recommended - and, as AWOL says, it will prolong the life of the relay contacts.
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Thanks for the replies.    I will add the fly back diode.   

John
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do it. I work for an electric car company, and they decided to not implement a diode across a relay/microswitch system, and the switches will fail after about a year. with a Panasonic part that has a built-in diode, there have been no issues.
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