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I have ESP-12F relay board, as per the following circuit diagram, however the 5V relays are triggering the moment power supply is provided to the board. I expect the optocoupler to trigger only when the GPIO pin connected to MCU is pulled down so I'm not sure why this is happening. I have also added a screen shot of Proteus simulation, validating the same. I am confused here.

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  • \$\begingroup\$ If AE is high and RC1-4 are low, the opto LEDs will switch on, thus switching the relay coils on. What is AE? Is this high at power up? Are RC1-4 low at power up? \$\endgroup\$
    – tim
    Commented Jun 19, 2021 at 15:02
  • \$\begingroup\$ Tip: Draw a schematic diagram that actually shows the schema of the circuit. I can't think of any good reason not to draw the relay driver transistors beside and connected to the opto-isolators. Similarly with the voltage regulators. Even in a simple circuit like this trying to find where each of the broken networks goes to wastes a lot of time and can only get worse on more complex circuits. If you're interested, here are some good Rules-and-guidelines. \$\endgroup\$
    – Transistor
    Commented Jun 19, 2021 at 16:51
  • \$\begingroup\$ i am sure your rules and guidelines for schematics would be helpful. any chance you found the issue in this circuit that i have shared @Transistor \$\endgroup\$
    – Suresh Kumar
    Commented Jun 19, 2021 at 16:54
  • \$\begingroup\$ No, we're awaiting your response to the first comment. \$\endgroup\$
    – Transistor
    Commented Jun 19, 2021 at 17:09
  • \$\begingroup\$ Can you capture it in your oscilloscope? Can to trace it back to where the glitch stems from? \$\endgroup\$
    – winny
    Commented Jun 19, 2021 at 17:13

1 Answer 1

Reset to default
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Your GPIO might be a logic 0 at power up.

Instead, connect pin #2 of the onto to GND, and drive pin 1 from the MCU (via the 10 k); invert the logic drive in your software.

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