Electronic – Use a relay as a resettable fuse

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I was thinking; If a relay is used to power a circuit AND itself, if the circuit is shorted – the relay should lose its own power and turn off – almost like a resettable fuse.

To power it up, I would have to bypass the relay temporarily.

Is this a valid use case? I was actually planning to use it as a "suicide switch" for my robot, but it seems this is an additional benefit?

PS: I'll keep my main fuse as well.

Best Answer

But the circuit controlled by the relay is isolated from the controlling circuit. A short in the controlled circuit does not necessarily cut power in the circuit which powers the coil which closes the relay contacts.

Even if the relay and the shorted load circuit share the same power supply, there is no guarantee that a short in the load leaves insufficient current for the relay to stay closed.

Of course, circuitry could be added for this. In fact relays are used for protection; for instance in some audio amplifiers, to cut speakers off from the amplifier in case of a fault that places a large DC voltage on the output. Why a relay might be used for this purpose is that it is transparent (does not add distortion to the signal).