On 07/01/17 22:00, David Woolley wrote:
> Some cheap mains operated lamps use capacitive droppers followed by
> rectifier and resistive current limiter. They are the type likely to be
> sold in one dollar stores, or on Ebay.
At least they are RF quiet! I have several in our house. No failure
The light from white "LEDs" is a mixture of a fairly narrow, blue, peak,
direct from the LED, and a broad, low, yellow one from the phosphor.
The fact that they don't excite the phosphor with UV is one of their
advantages, when compared with CFLs (where the actual physics is also
pretty much co
alter
Underwood
Sent: Saturday, January 7, 2017 8:08 AM
To: Elecraft Reflector
Subject: Re: [Elecraft] Dimmable LED desk lamp for operating position
recommendation needed
A brute force solution would be to get four LED lighting strips that run off
12V and use four switches. Turn on as much li
hat it
>> can
>>> generate enough voltage to overcome the LED's forward voltage (Vf), and
>> with
>>> an output current that's variable from 0mA to around 20mA (or whatever
>> the
>>> LED's maximum forward current (If max) is specified
anuary 06, 2017 8:17 PM
> > To: elecraft@mailman.qth.net
> > Subject: Re: [Elecraft] Dimmable LED desk lamp for operating position
> > recommendation needed
> >
> > A linear voltage regulator is very quiet. That's just a bipolar
> transistor
> > passing t
D6A
>
> -Original Message-
> From: Elecraft [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ron
> D'Eau Claire
> Sent: Friday, January 06, 2017 8:17 PM
> To: elecraft@mailman.qth.net
> Subject: Re: [Elecraft] Dimmable LED desk lamp for operating position
&g
Component count wise, a voltage regulator and a current regulator take about
the same number of components.
Controlling the (linear) current to an LED is an easy way to vary the
brightness, but the useable range is limited.
You can test this with a typical voltage & current regulated bench suppl
There will be a switching converter on any quality make of LED lighting.
The only way you avoid it is if they use a simple series dropper
resistor, which is not energy efficient.
LEDs are constant current devices, so there is no such thing as a 12V
LED (an LED with a 12V forward voltage drop
y, January 06, 2017 8:17 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Dimmable LED desk lamp for operating position
recommendation needed
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
supp
-boun...@mailman.qth.net] On Behalf Of Bill
Frantz
Sent: Friday, January 6, 2017 6:07 PM
To: elecraft@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 ha
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
On Fri,1/6/2017 7:24 AM, Craig Smith wrote:
Have a look at this one:
I'm using LED strip lights from Wired Communications. Discovered them
several years ago -- they sell at hamfests on the west coast. Do NOT use
their power supplies. But their strips work great on a wide range of DC
voltages
Greetings Peter …
Have a look at this one:
https://www.amazon.com/Dimmable-Stoog-Brightness-Rechargeable-Adjustable/dp/B01CSHZ99Y/ref=sr_1_10?s=home-garden&ie=UTF8&qid=1483715928&sr=1-10&keywords=usb+led+desk+lamp
I’m not claiming this is the highest quality lamp ever made. I also do not
curr
I've used this one for over a year, and pleased with it. My wire antennas
are only about 25 ft away and no noise issues:
https://www.amazon.com/gp/product/B00KSQ8ZNA/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1
Barry W2UP
--
View this message in context:
http://elecraft.365791.n2.nabble.com/D
\
> On Jan 6, 2017, at 2:00 AM, Peter D. Vouvounas wrote:
>
> I presume some of you have been through a selection process to find a usable
> dimmable LED desk lamp with articulating arm that does not create RFI back
> into your Flex on HF.
>
>
I mounted (dual side adhesive tape) an LED strip
I presume some of you have been through a selection process to find a usable
dimmable LED desk lamp with articulating arm that does not create RFI back
into your Flex on HF.
My current desk lamp (Halogen with mini bulb dimmable) makes a great deal of
noise in the 80 meter band and I'd like to repl
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