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I would like to make a switch which will be able to switch on/off 12-60V low current devices using nRF52840, optocoupler and mosfet. enter image description here I found this schematic and my idea was just to adjust R1 because voltage of GPIO of nRF52840 is 3.3v. I realized that source current of GPIO might not be enough to run optocoupler so I decided to look for low input current optocoupler. I found VO618A and my questions is would it be fine if I just switch PS2801 with VO618A and adjust R1? (I don’t have many experience with electrical engineering experience so any guidance/help is welcomed)

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  • \$\begingroup\$ Note that both couplers have Vce max 80V, which is fine for your stated 60V, but does not go well with 100V on schematic. \$\endgroup\$
    – Maple
    Apr 21, 2021 at 15:37
  • \$\begingroup\$ Thanks. Yes this 100V is wrong. I'm still concerned about limiting voltage on gate. Do you maybe have any suggestion how to solve it? \$\endgroup\$
    – shtepa
    Apr 21, 2021 at 19:34

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There's a couple of problems with your circuit - the mosfet won't like much over 20V on it's gate and your circuit doesn't limit it. The 100nF cap is of little use across the led of the opto - why did you place it there?

The opto coupler is really a waste of time - it adds very little. You'd be better off to chose a mosfet that has a logic level gate.

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  • \$\begingroup\$ I found schematic online \$\endgroup\$
    – shtepa
    Apr 21, 2021 at 12:20
  • \$\begingroup\$ "You'd be better off to chose a mosfet that has a logic level gate." I doubt there are many FETs with logic level going up to 60V. And if one has to drop gate voltage anyway, then what is the point of limiting choices to logic level parts? \$\endgroup\$
    – Maple
    Apr 21, 2021 at 15:30

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