Re: Very low power, power supply

From: John Woodgate (jmw_at_jmwa.demon.contraspam.yuk)
Date: 03/17/05 

Date: Thu, 17 Mar 2005 10:58:57 +0000

I read in sci.electronics.design that Paul Burke <paul@scazon.com> wrote
(in <39t14hF4mtp4kU1@individual.net>) about 'Very low power, power
supply', on Thu, 17 Mar 2005:
>Don Pearce wrote:
>
>> You don't need a power supply. Put all the LEDs in series with each
>> other, and with a 5.6k resistor. Get a resistor with a power rating of
>> about 5 watts.
>
>Or a 250Vdc/160Vac 0.47uF cap. (assuming 60Hz) (about 50p from Farnell),
>then it doesn't get warm.

You need some resistance in series to prevent the inrush current zapping
the LEDs and/or the cap. For 120 V mains, 470 ohms 0.5 W may be enough. 

-- 
Regards, John Woodgate, OOO - Own Opinions Only. 
The good news is that nothing is compulsory.
The bad news is that everything is prohibited.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

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