[Elecraft] Leds for W1

[Dave Van Wallaghen]

Good Morning Bill,

There has been a lot of back and forth on this, so let me share the 
direction I'm going to take on this.

I ordered red, yellow and green LED's made by Luxen that all have very 
similar specs. My guess is that they will be significantly less bright 
than the existing red LED's and that we would have to play with a 
resistor pack value that would provide the happy medium of brightness 
and current draw (and not stressing the LM78L05 as Jack has pointed out).

Doug has already experimented a little with this and found 470 ohms gave 
him the brightness he desired. At this point, I'm not sure what the 
current draw would be or if that is feasible with the LM78L05.

I believe that I might be able to come up with the right combination of 
LED's and resistor packs to obtain a decent level of brightness with 
uniformity between the LED's without compromising the design with an 
exorbitant current draw.

As I said yesterday, I will take current measurements before I start and 
make comparisons during the experimentation, hopefully arriving at a 
state that provides the happy medium discussed above. I should have most 
of the parts in here sometime early next week.

My desire is to have the least impact possible on the W1 design and 
minimize the impact on the builder as well. And hopefully we can provide 
this solution to new as well as existing units.

Then again, I may be all wet here ;-) I guess the worst case is that I 
have to buy another W1 from Elecraft ;-)

73,
Dave W8FGU



Bill Johnson wrote:
> It seems we need to find a set of colored LED's that give similar output as
> the reds....  With the research done so far, doesn't look at that likely. I
> wonder if there are other resources.  I wonder if a resistor pack of a
> slightly higher value than 470 might be a better compromise and change the
> value of the SWR reds so they won't draw more than the others. This would
> help reduce power draw.
> 
> 
> 73,
> 
> Bill
> K9YEQ
> K2 #35; KX1 #35; K3 #1744; mini mods
> 
> 
> -----Original Message-----
> From: Doug Joyce [mailto:d_joyce at sympatico.ca] 
> Sent: Friday, February 20, 2009 9:40 PM
> To: Bill Johnson; 'Dave Van Wallaghen'; 'Jack Smith'
> Cc: elecraft at mailman.qth.net; 'Ken Kopp'
> Subject: Re: [Elecraft] Leds for W1
> 
> Bill:  I've done some further testing and believe it's going to take
> increasing the current to approx 6 to 7 ma to get the new coloured LEDs to
> be bright enough.  That would involve reducing the 2.2 Ks to approx 470 ohms
> and finding a source for a suitable resistor pack.  At this higher current
> the red LEDs are still brighter than the other colours and there is no easy
> way to separately control the current to individual colours.
> 
> There are also a number of other things to check such as the ability of the
> U3 regulator to handle the increased current.  Battery life will also be
> reduced and perhaps this "coloured version" needs to be run from a wall
> wart.
> 
> 73
> 
> Doug,  VE3MV
> 
> ----- Original Message ----- 
> 
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