RE: 240v LED

["Kevin Hawkins" <lists@xxxxxxx>]

    LED's don't really have a voltage as such - they light up when a certain current flows through them - all you need to do is put a  resistor in series with the led (to limit the current) - it could go straight across 240V. However at high voltages because you are dropping a large voltage across the resistor it will get quite warm and therefore needs to be a high wattage variety - that's why most people don't do this - you might be better using a neon indicator - far more efficient. Most times LED's are used on the low voltage side of a transformer or psu. However if you must here's how...

 

    You need to find out what current the led would like (spec sheet) - normally in the 10 - 20ma range and calculate the resistor as follows   240/current required. e.g. 10ma gives 24K - nearest preferred value being 22K (11ma) or 27K. ( wattage of resistor required = i^2 x R - in above example using 22K  this works out to  .011 x .011 x 24000 = 2.66W. This is quite high - It will get quite warm and it will be quite bulky.

 

    Kevin

 

-----Original Message-----
From: Amar Nagi [mailto:groups@xxxxxxx]
Sent: 14 September 2002 12:45
To: ukha_d@xxxxxxxSubject: RE: [ukha_d] 240v LED

is there such thing as a 240v led which i could
use to indicate when a button has been pressed.
I am after something as small as possible.

any options ?


http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx
Subscribe:  ukha_d-subscribe@xxxxxxx
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx
List owner:  ukha_d-owner@xxxxxxx
List of UKHA Groups here - http://groups.yahoo.com/group/UKHA_Grouplists/

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

Yahoo! Groups Sponsor

ADVERTISEMENT

http://www.automatedhome.co.uk
Post message: ukha_d@xxxxxxx 
Subscribe:  ukha_d-subscribe@xxxxxxx 
Unsubscribe:  ukha_d-unsubscribe@xxxxxxx 
List owner:  ukha_d-owner@xxxxxxx
List of UKHA Groups here - http://groups.yahoo.com/group/UKHA_Grouplists/

Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.

<<attachment: winmail.dat>>