[RFI] LED Bulbs

[Dale]

David,

The biggest problem in trying to do what you suggest is CO$T.  Here is why:

1.  LEDS are low voltage devices and have poor PIV diode characteristics.  To drive them directly from a "good" lamp dimmer would require a series string of LEDS of around 50 to 60 devices, plus a series rectifier and filter.  You could also drive them from a variable autotransformer, but remember, the problem with LEDs is that the light output varies more with current than with voltage.  That's why all of these switching-topology ICs are on the market: they regulate CURRENT to the LEDs and of course, use PWM techniques.  

2.  The least expensive LED lights would be a simple series string of LEDs without any form of brightness control.  Add a half wave rectifier to handle the PIV, and you can make your own.  There will be some limited RFI from the diode action, but not much.  

3.  Using a low voltage scheme is very costly.  Since you can not drive a transformer with a conventional lamp dimmer, you would have to use a variable autotransformer ("Variac"), and you know how large and expensive they are.  That device could drive a conventional iron core step-down transformer to power the LED string, but not many folks would want to spend that level of money and put up with the gross size of the "controller".

For those who want clean, dimmable lighting, I suggest a known good dimmer (such as the Lutrons previously discussed in this forum) and either conventional incandescent or halogen bulbs.  It's tough to beat a resistor (lamp filament) for simplicity.

73, Dale
WA9ENA  


-----Original Message-----
>From: "qrv at kd4e.com" <qrv at kd4e.com>
>Sent: Feb 12, 2014 6:40 AM
>To: rfi at contesting.com
>Subject: Re: [RFI] LED Bulbs
>
>Or, use a LED system that is known-clean - or modify it to make
>it so - nearly every kind of electrical device is capable of RFI
>if improperly implemented.
>
>
>> In a word - yes.  If the LEDs each have a switching power
>> supply/driver, then changing to plain incandescent or halogen bulbs
>> would eliminate all of those RFI generators.
>>
>> 73, Dale WA9ENA
>
>
>
>-- 
>
>David (NOT Dave) Colburn, KD4E - Nevils, Georgia USA
>
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