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-   -   heater supply (xformer specs are 6.3V 2.5A) as supply for a power LED? (http://www.diyaudio.com/forums/tubes-valves/17724-heater-supply-xformer-specs-6-3v-2-5a-supply-power-led.html)

jarthel 15th July 2003 02:34 AM

heater supply (xformer specs are 6.3V 2.5A) as supply for a power LED?
 
as title. Thank you.

Jayel

JOE DIRT® 15th July 2003 02:42 AM

sure why not....a diode and 220 ohm resistor and your good to go

SHiFTY 15th July 2003 04:51 AM

LEDs don't like AC very much, you would have to rectify it first... Why not use a 6.3V globe or better still, a "pigtail" neon over teh mains...

Sch3mat1c 15th July 2003 07:02 PM

They can take 8PRV.

Tim

EC8010 17th July 2003 09:38 PM

A cheap and cheerful method would be to put a 1N4148 across the LED (in the opposite direction), then add a 1k resistor in series with the whole lot, and bung it across your 6.3VAC. You may find that you notice the flicker, though.

vacuumhead 20th July 2003 06:17 PM

Simplest - put 1K in series with your LED. No rectification needed. I build like this, and everything works just fine. If you need to know this - for every volt on power supply for LED put 100 Ohms. Higher than that will only dim LED slightly.
Jack

EC8010 20th July 2003 06:33 PM

Agreed, the LED will self-rectify, and the 1k resistor limits reverse current, but it's a bit naughty. Also half-wave rectification means that you pass DC through your transformer, which is also undesirable. 1N4148 is so cheap (a penny) when you buy 100 that you might as well use it...

Sch3mat1c 20th July 2003 08:35 PM

Ooooo.. 20mADC on a 3A winding... it won't even notice it's there :clown:

Tim

jeffreyj 20th July 2003 11:00 PM

If a transformer is not specifically designed to accommodate DC current, then no amount is appropriate. None. It is bad engineering practice, looks shoddy, and, degrades virtually every AC parameter of the transformer to save a measly pence, if that.

Sch3mat1c 20th July 2003 11:56 PM

Any transformer will tolerate DC. Period. How much depends on construction.

It would be a pretty damned crappy transformer if it couldn't tolerate a mere 1% DC current.

Tim


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