While building a home automation system, I triggered my 5V relay through the Arduino (running the blink code, 1 second ON 1 second OFF), however my relay stays in the triggered state. Due to which the light stays ON. I don't understand this behavior. After I disconnect the AC connections, a minute later the relay starts behaving the normal way. Are the relays faulty? Is there something causing the latch?

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    \$\begingroup\$ Are you sure it isn't a latching relay? Have you exceeded the relay's specs? \$\endgroup\$ Dec 18 '16 at 10:57
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    \$\begingroup\$ Show us pictures of the relay, especially the ratings. Add the schematic of the relay and relay driver. Please check the signals with a multimeter to ensure they're as expected. \$\endgroup\$ Dec 18 '16 at 11:10
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    \$\begingroup\$ I don't have a relay driver in between the relay and the Arduino. Is that required? \$\endgroup\$
    – badrobot15
    Dec 18 '16 at 11:22
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    \$\begingroup\$ Maybe needed, show us what parts you are using. \$\endgroup\$
    – Jasen
    Dec 18 '16 at 11:34
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    \$\begingroup\$ You require a driver circuit between the Arduino and the relay - otherwise you WILL kill your Arduino. \$\endgroup\$
    – Majenko
    Dec 18 '16 at 12:13

Relays are mechanical switches it could be possible that the switching time is very less for the internal switch to come back to it's original form. If you are using it to control AC you can consider using SCR or a Triac. If you want to continue using the relay you can put an Optocoupler IC such as MOC3021 in between to solve this problem.


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