3truckheisler

I am building a turntable for my layout and have designed and built the control panel. On the control panel I have LEDs to indicate the spar I selected and LEDs when the bridge is in place. I am a retired Electrical Engineer so I know all about reducing the current/voltage to reduce output of these LEDs. Without getting into the design, these are in series and parallel with other components so voltage changes are not an option since it affects too many other things.

Has anyone ever painted, sanded or in some other way changed LEDs to reduce their output? I'm about to try experimenting, but if this wheel has already been invented it would certainly save time trying things that don't work.

Thanks!

Reply 0
Prof_Klyzlr

Dear 3-Truck, As LEDs are

Dear 3-Truck,

As LEDs are current devices, varying the voltage is not the brightness-controlling factor. Unless you are somehow relying on a specific milliAmp current flow thru each LED, surely a discrete dropping resistor per LED is still an option?

Alternatively, what about an inline adjustable current regulator/LED controller, such as 
http://www.ledsales.com.au/catalog/index.php?main_page=product_info&cPath=148_182_236&products_id=384??

If you must use an "analog solution" (love that term ),
and swapping out the LEDs for units with lower-brightness is not an option,
then possibly a diffuser, which is nothing more than a piece of non-waxy baking paper, might help?
(I've used such a technique to diffuse and "dim" 12V halogens for layout-lighting missions previously)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

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3truckheisler

All I wanted to do was use

All I wanted to do was use some sort of optical filtering to reduce the brightness as it is overwhelming. I considered using thinned ink or paint and/or sanding the surfaces of the LEDs to reduce the luminescence. I had not thought of your wax paper idea, but it sounds like a great avenue to pursue. I know of a couple things I can try to both darken the wax and possibly make it transfer to the LEDs permanently.

As I mentioned I do not want to alter the voltage or current. I have spent my professional life designing electronic circuitry so I know how current affects the LED's output; however the minimum voltage/current requirements for making a LED illuminate in this situation still makes it too bright relative to other LEDs on the board (green & red LEDs illuminate at different levels). Since the difference in luminosity vs voltage is not linear, and since there are other components (in series and parallel), changing the voltage/current is not an option. I worked on the voltage/current issues for the whole design early on, but when it all came together in the real world the brightness is unbelievably different even when the green LEDs are "barely lit", so the issue is not one of electrical, but optical. (By the way, I've tried several other manufacturer's LEDs to see if that might help, but no such luck!

Your great suggestion with the  wax paper is an excellent idea for this!

Thanks for the help!

Reply 0
vasouthern

Dremel tool.

I took the cut off disk on a dremel and sanded the face of T3 LEDs flat for signals. I carefully sanded them. The result for the signals was removing the round end and the light looks more like a signal light with the bright center and dim around the edge.

This should also work on the larger sized LEDs. Be careful sanding tho, do it outside or consider a mask. Its plastic and not good to breathe the dust.

 

Randy McKenzie
Virginia Southern - Ho triple decker 32x38

Digitrax Zephyr, DCC++EX, JMRI, Arduino CMRI
On Facebook:   http://www.facebook.com/groups/485922974770191/

Proto freelance merger of the CRR and Interstate

Based on the north end of the Clinchfield.

 

 

Reply 0
Ironhand_13

By non-waxy

are you referring to baking paper, as in parchment paper (not the U.S. Constitution's paper, but paper for baking)?  Any chance of some before and after pics of the baking paper idea?  I've never baked with such paper, so have none lying around to try out.  Also, I've used thinned acrylic paint to dim an LED or two, but never sanded one.  Would just using some 400-grit wet-dry paper act as a diffuser too?  I have some blue LEDs on my control panel that just about blind you if you squat and look at them head-on, even from a great distance, so I like these ideas so far.

-Steve in Iowa City
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Geoff Bunza geoffb

Sometimes simple is best

Gents, Get a bottle of Tamiya clear color to your LED color (acrylic), add a touch of black acrylic, mix, apply in light coats to Dim to your taste and you're done! Best regards, Geoff Bunza

Geoff Bunza's Blog Index: https://mrhmag.com/blog/geoff-bunza
More Scale Model Animation videos at: https://www.youtube.com/user/DrGeoffB
Home page: http://www.scalemodelanimation.com

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