RE: LED rules of thumb

[ian.bird@xxxxxxx]

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


                                                                                                                                        
                     
"Bricknell,
Tony"                                                                                                 
                     
<tony.bricknell@tycoelect       
To:      
ukha_d@xxxxxxx                                                 
                     
ronics.com>                     
cc:                                                                              
                                                      
Subject:  RE: [ukha_d] LED rules of
thumb                                        
                     
17/09/02
15:09                                                                                                    
                     
Please respond to
ukha_d                                                                                          
                                                                                                                                        
                                                                                                                                        




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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