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

jarthel · 15th July 2003, 02:34 AM

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

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

15th July 2003, 02:34 AM	#1
jarthel diyAudio Member Join Date: Jan 2002 Location: somewhere in Australia	heater supply (xformer specs are 6.3V 2.5A) as supply for a power LED? as title. Thank you. Jayel

15th July 2003, 07:02 PM	#4
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	They can take 8PRV. Tim __________________ Seven Transistor Labs Projects and Resources

17th July 2003, 09:38 PM	#5
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	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. __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

20th July 2003, 06:33 PM	#7
EC8010 diyAudio Moderator Emeritus Join Date: Jan 2003 Location: Near London. UK	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... __________________ The loudspeaker: The only commercial Hi-Fi item where a disproportionate part of the budget isn't spent on the box. And the one where it would make a difference...

20th July 2003, 08:35 PM	#8
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	Ooooo.. 20mADC on a 3A winding... it won't even notice it's there Tim __________________ Seven Transistor Labs Projects and Resources


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15th July 2003, 02:42 AM	#2
JOE DIRT® diyAudio Member Join Date: Apr 2003 Location: Brantford, ON	sure why not....a diode and 220 ohm resistor and your good to go

15th July 2003, 04:51 AM	#3
SHiFTY diyAudio Member Join Date: Jul 2002 Location: New Zealand	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...

20th July 2003, 06:17 PM	#6
vacuumhead diyAudio Member Join Date: Jul 2002 Location: South Africa	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

20th July 2003, 11:00 PM	#9
jeffreyj diyAudio Member Join Date: May 2003 Location: Tampa, FL	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. __________________ Before you make that audacious claim, check this site out:QAudio Myths

20th July 2003, 11:56 PM	#10
Sch3mat1c diyAudio Member Join Date: Jan 2003 Location: Milwaukee, WI	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 __________________ Seven Transistor Labs Projects and Resources

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