[Elecraft] Dimmable LED desk lamp for operating position recommendation needed

[Ron D'Eau Claire]

A linear voltage regulator is very quiet. That's just a bipolar transistor
passing the current with adjustable base voltage. I use them on my HB power
supplies for the same reason. No square switching, no RFI. 

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill
Frantz
Sent: Friday, January 6, 2017 6:07 PM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] Dimmable LED desk lamp for operating position
recommendation needed

To avoid color shifts with dimming, most LED dimmers use Pulse Width
Modulation (PWM). PWM has the potential to generate RFI, so be careful. The
LEDs themselves should be very quiet. Using LEDs with resistors to limit the
current should also be quiet. A system that switches LEDs for brightness
control would be a safe solution, but I don't know of any commercial systems
which do this.

On the other hand, I have not noticed a problem with the LED dimmers in my
house, so perhaps most of the problem is in the wall-wart power supply.

73 Bill AE6JV

On 1/6/17 at 3:50 AM, elecraft at mailman.qth.net (Marc Veeneman via Elecraft)
wrote:

>I mounted (dual side adhesive tape) an LED strip to the underside of an 
>equipment shelf.  The strip came with a 12v switcher that I ignored.  I 
>use my 12 volt supply.  The strip was, I think, 24 inches long and has 
>a dimmer that can be inserted in the power lead.  No RFI.  Plenty 
>bright.  Mine came from Amazon but there are many to choose from these 
>days; you can even select color temperature when you order.
-----------------------------------------------------------------------
Bill Frantz        | Truth and love must prevail  | Periwinkle
(408)356-8506      | over lies and hate.          | 16345 
Englewood Ave
www.pwpconsult.com |               - Vaclav Havel | Los Gatos, 
CA 95032

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