The Triac is a thyristerīoth types are normally off but may be triggered on by a low current Power to be controlled is unidirectional. Typically thyristor causes voltage drop of 1-1.5 V when it passes theĪ Silicon Controlled Rectifier is one type of thyrister used where the (ideally) dissipate very little power as they are either fully on or fully off. The advantage of thyristors over simple variable resistors is that they Power getting to the bulb is adjustable, and hence the light (the picture should look like sine wave):Īnd here is what gets to the light bulb when the dimmer firesĪs you can see, by varying the turn-on point, the amount of Here is an example of normal AC power you get from the receptacle

You trigger the triac you change the duty cycle and therefore Goes to zero (exactly at the next zero crossing if the load is purely Is triggered it keeps conducting until the current passing though it When the thyristor is triggered relative to the zero crossings of theĪC power is used to determine the power level. Typical light dimmers are built using thyristors and the exact time Solid-state dimmers use the brightness knob setting to determine at what point in each voltage cycle to switch the light on and off. Get the full AC voltage, because it get's less power to heat the filament. The light bulb will appear to be much less bright than when it Of the full AC voltage that is applied to the lights being controlled.įor example, if the voltage is applied for only half of each AC cycle, Solid-state light dimmers work by varying the 'duty cycle' (on/off time) Like homes, restaurants, conference rooms and in stage lighting. This type of electronic light dimmersīecame available after 1970 and are nowadays used in very many locations Electronics controlling also made possible to make them easilyĬontrollable from remote location. Quite easy to make small and inexpensive light dimmers which have goodĮfficiency. The power electronics have proceeded quickly since 1960. Have poor efficiency and they are hard to control from remote location. Those light controlling methods have been that they are big, expensive, Used in movie theatres, stages and other public places.

Power resistors and adjustable transformers.

Light dimming has been possible for many decades by using adjustable Light dimming is based on adjusting the voltage which gets to the lamp. There is no guarantee as to the suitability of said circuits and information for any purpose whatsoever other than as a self-training aid. The contents of the articles below might be totally inaccurate, inappropriate, or misguided.

European EMC requirements on dimmers Disclaimer.

120v dimmer for led lights