Re: [Elecraft] Dimmable LED desk lamp for operating position

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

Re: [Elecraft] Dimmable LED desk lamp

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

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

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 light a

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

ed to be designed so that 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 ma

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

> > Hope this helps. > > > > Cheers es 73, > > Dave > > AD6A > > > > -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 &

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

; 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 > recommendation needed > > A linear volta

Re: [Elecraft] Dimmable LED desk lamp

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

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

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

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

@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 supplies for the same reason. No square switching

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

...@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 has

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

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

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

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

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=UTF8=1483715928=1-10=usb+led+desk+lamp I’m not claiming this is the highest quality lamp ever made. I also do not currently have a way

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

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=1 Barry W2UP -- View this message in context:

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

\ > 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

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

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