RE: LED rules of thumb

["Stu Worrall" <stuart@xxxxxxx>]

Cool!  And thanks for the diagram.  It really helps to visuallise
these
things when im a complete novice to electronics :-)

In terms of the current required Ive been looking at the unit that Ian
recommended to Kieran which is on screwfix. 

http://www.screwfix.com/app/sfd/cat/pro.jsp;jsessionid=O4ONBAKXEIPG3CJO2
C4CIIQ?ts=71138&id=14990

Only probs for me is that it specifies 12V and 60 Watts.  Is there
a
calc to work out what this would provide in milli amps??  Any ideas
on
the spec that you've already looked at Ian?

Thanks

Stu

> -----Original Message-----
> From: Bricknell, Tony [mailto:tony.bricknell@xxxxxxx] 
> Sent: 17 September 2002 15:10
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] LED rules of thumb
> 
> 
> An easy solution would be to do this (time for bad ASCII art)
> 
> --------------------------- 12V
>            
    
>   -      -   
-    - 
>              
>   R          
>              
>   -      -   
-    -
>            
    
>  ---    ---  ---  ---
>  \ /LED \ /  \ /  \ / etc, etc.
>  ---    ---  ---  ---
>            
    
> ---------------------------- 0V
> 
> Following this example, 20 LED's are going to draw 20mA each 
> - total current demand from 12V supply = 20 * 0.02 = 0.4  
> Therefore make sure wall-wart can provide 400mA at 12V.
> 
> LED wants 20mA at 2.1V (again, all made-up figures - you'll 
> need to substitute your values from the  manufacturers data
sheet)
> 
> R = V / I = 9.9 / 0.02 = 495 ohms (use nearest higher value, 560
ohms)
> 
> HTH
> Tony
> 
> 
> -----Original Message-----
> From: Stu Worrall [mailto:stuart@xxxxxxx]
> Sent: 17 September, 2002 14:55
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] LED rules of thumb
> 
> 
> Complete electronics thicko here im afraid but what if I 
> wanted to put 20 in a line to go down the garden?  Im 
> assuming I will need a resistor for each LED and a 12V 
> supply.  So the big question for me is do they go in parallel
> or series and can I get away with this many on one line?
> 
> Thanks
> 
> Stu Worrall
> 
> <snip>
> 
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