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I will be turning a relay on from my circuit by sending a signal 500ms to 1000ms long, and i am trying to protect against poor wiring or faulty relay from the user that causes a short circuit on the relay which could blow the fuse on the module

The power supply is rated for 2A and the fuse on the module is rated for 1A. I would like to create a protection that even if there is some short circuit on the relay output the fuse cannot blow,

My solution was to add a resistor on series of the relay, but this would mean that resistor should have atleast 5watt rating for it to survive, or a high value resistance for it to survive. Having a high resistance also might mean that the relay might not turn on because there wont be enough voltage that will cross it.

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Paralleling a resistor to the relay seem kinda useless also since the current will not flow to the resistor but to the short instead.

How should i approach this? i possible how can this be done with basic components (resistor,capacitor,diodes etc)

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    \$\begingroup\$ Consider a polyfuse. \$\endgroup\$
    – Hearth
    Commented Nov 24, 2019 at 17:51
  • \$\begingroup\$ Typical 5v relay coil has resistance of about 125 ohms. Also relay requires certain amount of power to work (5v versions usually about 0.2W). This means you cannot put any significant resistor in series. As @Hearth suggested, polyfuse is probably best option. Choose value between normal coil current and 1.0A. I think it would be something about 200 mA \$\endgroup\$
    – Zhenek
    Commented Nov 24, 2019 at 18:08
  • \$\begingroup\$ @Hearth i forgot to mention a polyfuse is kinda slow the main power supply over current feature would trigger before the polyfuse do and shuts the whole system down \$\endgroup\$
    – Jake quin
    Commented Nov 25, 2019 at 12:54

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