[R-390] Re: LED lamp replacement

[Rbethman]

Bob - Thanks!  Makes perfect sense to me - Even though I'm a Pollack 
that makes Kielbasa!

<g>

Bob - N0DGN

Bob Camp wrote:

> Hi
>
> Assuming you really want to go this way here's the basic data:
>
> Page 1333 in the online Digikey catalog (www.digikey.com) has a number 
> of high intensity LED's. They come in several colors and in white.
>
> The voltage drop on the colored ones is a little under or a little 
> over 2 volts depending on the color. The white ones have a voltage 
> drop of 3.6 volts.
>
> If you run them off of the 25 volt AC supply you will have about  33 
> volts DC to work with. If you drop about 1/3 of the supply across the 
> series resistor then you get 22 volts on your string of LED's.
>
> The resistor is sized to give you 20 to 30 ma through the LED's. 
> Eleven volts and 25 ma would get you a 440 ohm resistor. 390 and 470 
> are the closest standard values. A one watt size should work ok. The 
> value will take a little fiddling to get the voltage right. I would 
> start at about 390 and work down to about 180 ohms.
>
> From there on it's a matter of picking a color and  figuring out how 
> many of them add up to 22 volts. If say 11 orange LED's does not make 
> sense then the resistor size can change to match the new load.
>
> A full wave bridge of 1N4148's to convert the AC to DC and maybe a 10 
> uf 35 volt cap across the stack of LED's completes the project.
>
> The resulting circuit looks like:
>
> Four diodes in a bridge, AC ends to the 25 VAC filament line and to 
> ground. DC ends to the resistor and diode / 10 uf cap combination. 
> LED's all go in series with each other.
>
> That may not be clear enough to follow along .... sorry about that.
>
>     Enjoy!
>
>         Bob Camp
>         KB8TQ
>
>
> On Jul 7, 2004, at 3:50 PM, Rbethman wrote:
>
>> First - When you get a new car or truck with those LED taillights, 
>> remember how WELL they get the attention of those behind you.  You'll 
>> live LONGER.
>>
>> Second - I'd like to get circuit info on LEDs in lieu of the dial 
>> lamps.  Whom can send it by mail?  Does someone have this on a web site?
>>
>> I may even tackle the UV for the meters!
>>
>> Bob N0DGN
>>
>> Kenneth G. Gordon wrote:
>
>
>

-- 
<                      Bob Bethman - N0DGN
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