RE: LED rules of thumb

[ian.bird@xxxxxxx]

> Any ideas on the spec that you've already looked at Ian?

I was just making sure it was a dimmable transformer and have not looked
at
these specifically. Someone else on the list said they had used them
and
they were fine.

Ian

Ian Bird
CibaVision UK Ltd.
Direct dial 01489 775570
Fax           01489
779570


                                                                                                                                     
                     
"Stu
Worrall"                                                                                                  
                     
<stuart@xxxxxxx       
To:      
<ukha_d@xxxxxxx>                                               
                     
erve.co.uk>                  
cc:                                                                              
                                                   
Subject:  RE: [ukha_d] LED rules of
thumb                                        
                     
17/09/02
16:10                                                                                                 
                     
Please respond
to                                                                                              
                     
ukha_d                                                                                                         
                                                                                                                                     
                                                                                                                                     




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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