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 BulbDial LED beam angle issue
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By: Anonymous: Simmo () on Wednesday, May 30 2012 @ 11:48 AM PDT (Read 1586 times)  
Anonymous: Simmo

G'day, I have just completed a recently purchased BulbDial kit. Everything is functional, but I've noticed the appearance of the display - using both the standard and the rear-projection face - is different from the many photos and videos available online. Specifically I think this relates to the beam angle of the LEDs, they seem to be quite wide angle, resulting in noticable 'shadowing' of the blue and green LED bodies around the periphery of the display. Also, my seconds hand is very washed out, adjusting white balance hasn't made much difference. IMHO, the LEDs supplied with this new batch of kit seem to be of highly variable (cheap) quality - one blue LED was very poorly constructed - the central 'cup' was offset in the encapsulation producing a highly offset, very wide beam and had to be desoldered and replaced with one of the supplied spares. Has anyone else experienced this shadowing problem (with dark semi-circles around the rim)? Is this due to poor alignment of the LEDs? I've tried some re-pointing with no significant improvement. Would replacing the lower ring (blue LEDs) with 3mm devices help? I'm thinking the shorter bodies would not be illuminated by the LEDs in the upper rings and produce less shadow. Perhaps I should just replace all the LEDs with better quality narrow beam angle devices? I'll try attaching a photo, but during the preview of this post I get an error "Specified upload directory, forum/media is not a valid directory" so I don't know if it will work. Thanks in advance.





       
   
By: Windell (offline) on Wednesday, May 30 2012 @ 12:17 PM PDT  
Windell

We have recently changed the type of LEDs provided in the kit to ones with a wider viewer angle. This is the type that we had originally planned to use when we first released the kit, but it has taken us some time to source them. There is (and always has been) shadowing of lower rings of LEDs. However, it is admittedly more noticeable with the wider-angle LEDs. One thing that can help is to move the blue and green LEDs somewhat "down and back" so that they're a little more recessed.

I'm sorry to hear about the bad LED-- that's a failure that I haven't seen before, and I'm glad that there was a spare there for you.

If the seconds hand is "washed out," you probably need to turn down the brightness of the other two rings. It is also possible to reduce the values of resistors R1-R6 somewhat, to get a little extra brightness, if that's what you'd like to do.


> Would replacing the lower ring (blue LEDs) with 3mm devices help?

Possibly, but the LED size is just one factor to consider-- you'd also need to make sure that the brightness and angle are suitable.


Windell H. Oskay
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By: Anonymous: Simmo () on Wednesday, May 30 2012 @ 01:01 PM PDT  
Anonymous: Simmo

OK, thanks for your quick reply. I think I understand the issue a bit better now, I have removed all the blue LEDs with the intention of rebending the leads to place them further 'out' and under the blue PCB. I have reinstalled one blue LED to test the aiming but I'm now getting spurious red LEDs illuminating in the blue test mode. I'm thinking this is because only one blue LED is fitted and this problem will go away when all the others are fitted - is this correct (a mux wiring issue?).

I also think I'll replace the red LEDs with new ones with longer leads and place them further in towards the center. This won't affect the visibility of the dial because I intend using the rear projection face.

Thank you.





       
   
By: Windell (offline) on Wednesday, May 30 2012 @ 01:14 PM PDT  
Windell

That's a fine approach, especially with the rear-projection option.

I'm thinking this is because only one blue LED is fitted and this problem will go away when all the others are fitted - is this correct (a mux wiring issue?).

Yes. The charlieplexing produces some strange effects when some (but not all) of the LEDs are in place.


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