PROBLEMS WITH LED LAMPS?
Question by Ewen:
Problems with LED lamps?
Ok, so basically I am working on a project an the moment. I want to create an innovative, energy-efficient lighting design using new technology such as LED lamps.
The basic specs of the lamps are as follows:
12v
MR16 fitting
Dimmable
White (ish) light
The problem is, I am a bit confused with how to incorpoate a mains voltage to 12v transformer into the circuitry. I am also confused with the term ‘Trailing edge dimmer’, which seems to be something I need if I am to use a dimmable LED bulb.
Can anyone help me? I need some directions as to what to do.
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Answer by wires
You need to run the mains to the transformer and then do everything with the 12 volts. Rectify and filter the 12 VAC to a decent 12 VDC. You probably cannot use a trailing edge dimmer as these operate on AC and LEDs operate on DC. It would not make any difference if you used a trailing edge or leading edge dimmer, you will not get the results you want. LEDs also do not respond well to voltage dimming. The light output varies very tiny with a fairly massive voltage reduction. You should look into PWM (pulse width modulation) for controlling the light output from an LED. This works by simply pulsing the voltage through the LED very fast. When the LED is off for about half the time that it’s on it appears dimmer. For more information on dimming LEDs check the links below.
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