RE: LED rules of thumb

["Stu Worrall" <stuart@xxxxxxx>]

That's handy to know about the double insulation.  I was thinking
about
including the resistor next to the LED but it sounds like yours are
located in the distribution box?  I could do with running one wire
so
Ill try to find a way around it and post progress.

Stu

> -----Original Message-----
> From: ian.bird@xxxxxxx 
> [mailto:ian.bird@xxxxxxx] 
> Sent: 17 September 2002 15:38
> To: ukha_d@xxxxxxx
> Subject: RE: [ukha_d] LED rules of thumb
> 
> 
> 
> Hi Stu
> 
> This is how I have done my front garden lights (the pretty 
> blue ones at www.mollyology.com then projects). The lights 
> all run from a distribution block - OK, stripboard and 3.5mm 
> plugs and jacks in a box. I did it this way to ease 
> replacement but so far they have been 100% reliable. I used 
> double lots of shrink wrap to weatherproof them, a small one 
> over each leg and the solder then a larger one over the LED 
> itself and down the wire for an inch and a half. I also used 
> 470r resistors and the total draw is around 300 ma for 16 LED's.
> 
> Ian
> 
> Ian Bird
> CibaVision UK Ltd.
> Direct dial 01489 775570
> Fax           01489
779570
> 
> 
>                                                              
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"Bricknell,
Tony"                      
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<tony.bricknell@tycoelect       
To:    
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ukha_d@xxxxxxx                                    
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ronics.com>                     
cc:    
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> Subject:  RE: [ukha_d] LED rules of
thumb                    
>                    
>                      
17/09/02
15:09                         
>                                                              
>             
>                      
Please respond to
ukha_d               
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> 
> 
> 
> 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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