Using a Light Dimmer or Similar Device as a Variac?
The quick answer is: No, get a proper Variac! The behavior of a phase control device like a light dimmer depends critically on what sort of load it sees. If the dimmer sees mostly a resistive load, it will work reasonably well and survive. However, most electronic equipment doesn’t fall into this category. If the dimmer is attempting to drive a piece of equipment with a lot of capacitance or inductance, at the very least it will behave strangely with the control range squashed to one end or the other, or the output voltage will change suddenly rather than smoothly. But more likely, it will self destruct and/or damage the equipment due to the strange waveform, which may result in a peak output voltage that approaches full line voltage even at relatively low settings. There’s also usually a minimum load below which it won’t do anything predictable. In short, get a proper Variac. You know my motto: “You can never have too many Variacs!”. 🙂 Surplus Variacs are readily available including
