[time-nuts] Reducing lab noise with LED lighting.

Bob Camp lists at rtty.us
Mon Sep 17 15:51:57 UTC 2012


Hi

I think you will find that a constant current source is what you are after
as a driver. That's not a hard thing to do, if you plan for it from the
start. 
I'd be careful about just which switcher you decide to use. A switcher
that's plenty quiet inside a PC case can be a bit noisy when attached to 50'
of wire. I've spent a lot of time swapping out conventional light ballasts
to get a lab that's quiet enough for phase noise work...

Bob

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Tom Knox
Sent: Monday, September 17, 2012 11:09 AM
To: Time-Nuts
Subject: Re: [time-nuts] Reducing lab noise with LED lighting.


I think I poorly explained my thoughts. I noticed on eBay that high powered
raw LED arrays like this one 
20W Warm White LED Lamp Chip 2800-3500K Bright Light Bulb... (170902780218)
are now for sale at reasonable prices. Do not let the wattage's fool you, If
you have not seen one of these arrays you will be shocked.
the 10 watt version usally use 12 volts, Most of these 20-100 watts run on
36vdc, I do not think driving these with a clean switcher will add to lab
noise VS CFL. One of my benches has standard 2 x 48 inch florescent  tubes.
I was going to mount 5 of these on a 48 inch aluminum extrusion with the
supply inside the old fixture. This would be very very bright (Perhaps to
bright) with just over 100 watts draw.
The conversion will cost about $100 on the surplus market if you had none of
the needed items and should pay for it self over the next few years in
energy costs.
Thomas Knox



> From: tholmes at woh.rr.com
> To: time-nuts at febo.com
> Date: Mon, 17 Sep 2012 10:21:07 -0400
> Subject: Re: [time-nuts] Reducing lab noise with LED lighting.
> 
> Some of the LED assemblies are stacks of diodes and the Vf is 2.5 to 3.5
> volts. How about powering them from a 3.3 volt PC supply? Plenty of amps
> available and those switchers have typically had to have their EMI
emissions
> cleaned up.
> 
> Tom Holmes, N8ZM
> Tipp City, OH
> EM79
> 
> 
> > -----Original Message-----
> > From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> > Behalf Of Tom Knox
> > Sent: Sunday, September 16, 2012 8:09 PM
> > To: Time-Nuts
> > Subject: [time-nuts] Reducing lab noise with LED lighting.
> > 
> > 
> > In this green era here in the USA there is a big push toward CFL
lighting.
> Problem
> > is I can see my CFL lighting on my PN measurements and other equipment.
I
> am
> > finding it is very noisy so I have started researching cost effective
LED
> lighting
> > and was amazed at what is available. On eBay there are 10 to 100 watt
raw
> chips
> > for $2-25.00  but that is equal to about 5 times the lumen of
incandescent
> lighting.
> > I was going to try building the heat sinks and supply into my existing
> bench
> > fixtures.
> > I will post more info soon.
> > Thomas Knox
> > 
> > 
> > 
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> 
> 
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