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  • MarkS654 commented on EasyIoT's instructable ESP8266 - $5 internet connected switch3 weeks ago
    ESP8266 - $5 internet connected switch

    It doesn't make sense, I'm afraid - there are traces of a couple of misunderstandings there. The ESP cannot supply enough current to drive a relay, and that's what you need a driver (e.g. the transistor) for, but in this circuit that does NOT increase the voltage - in fact (again, in THIS circuit) it decreases it. In the circuit as drawn, the relay is going to see a voltage of about 2.7v: it's being powered by a 3.3v supply, and you're going to lose about 0.6v of that across the transistor. Now, perhaps the relay will still work at 2.7v - I haven't tried - though it's not guaranteed. Really you either need a lower voltage relay, or a higher voltage supply for the relay. A supply giving 5v for the relay and 3.3v for the ESP would do nicely.

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