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It's pretty straightforward to use transistor as a switch while working with DC voltage. But I am faced with a situation to switch on/off an AC motor (single phase).
Is it absolutely necessary to use a TRIAC or SSR? A stupid question maybe, but what would happen if I were to just make use of a BJT? Would it burn out?
I am trying to build an Arduino project which uses a DC motor following the steps in this Instructables article, but happen to have several AC motors lying around without any use.
The capstan motor of one of my tape decks is speed controlled by a transistor that shorts a bridge rectifier - it should work for on-off control too.
simulate this circuit – Schematic created using CircuitLab
The tape deck uses a transformer to isolate the motor 9and the control circuit) from the AC mains, however, the same control could be achieved using an optocoupler to isolate the control circuit from the transistor and motor, which then can be connected directly to 220V.
The first problem that springs to mind is that you will damage the base-emitter region when the ac reverse biases the transistor. Base-emitter regions are normally specified as being able to handle a reverse voltage of between 5 and 10 V max.
Maybe you should use a dual back-to-back mosfet solution: -
This circuit is used inside solid-state-relays. But beware - the photo-voltaic opto-isolator hasn't got great switching speed so PWM doesn't work too well.
