Christmas lights

Discussion in 'General Electronics Chat' started by PG1995, Aug 14, 2011.

  1. PG1995

    Thread Starter Well-Known Member

    Apr 15, 2011

    I think the blinking of Christmas light could be controlled by several different mechanisms. Such as using magnetic relay switch, an oscillator, or bimetallic strip. The on and off effect of the lights can be achieved using relay switch, bimetallic strip, or square wave oscillator. But if one wants the lights to dim slowly, then go back to full brightness and so on, then one needs to use sine wave oscillator. Do I make sense? Please let me know. Please remember that I don't have that much knowledge about this stuff therefore please keep your reply simple. Thank you.
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    Your facts are understandable. Is understanding your question, your only question?
  3. Adjuster

    Late Member

    Dec 26, 2010
    There is no definite requirement for a sinewave oscillator of the simple kind that you may be imagining. Such an oscillator could be used in an analogue system, but a sinewave oscillator to run at a very low frequency (perhaps less than 1Hz) is not so very convenient to make. A triangle-wave oscillator might be easier at such a low frequency.

    Nowadays, the "sinewave" oscillation would often be provided by a digital system, a sort of scaled-down computer which calculates a series of numerical values to give a more or less sinusoidal variation with time. This could be used to generate a varying voltage or current using an Analogue to Digital Converter, so as to control the lamp current.

    More commonly, a system called Pulse Width Modulation would be used. The lamp brightness would be controlled by varying the width of a pulse used to turn on the lamp current for part of the time - the pulses being repeated so rapidly that the flickering is invisible to the human eye. Edit: such a system would use MOSFETS, bipolar transistors, or other reasonably rapid switching devices - mechanical relays are too slow for this.