Hi everyone:
As some of you are aware I am working on a Bachmann Spectrum Fairbanks Morse H-16-44 installing sound etc. etc.
I have run into a challenge with the number boards. The original Bachmann number board lighting was rather weak. I am trying to give the number boards somewhat brighter and more even lighting but I am not having too much success.
My question is how can I get even lighting across the entire number board? I have tried several different LEDs including a pair of LEDs side by side but the light still does not come through the number board evenly. There is always a bright spot directly behind where the LED(s) are with little light to the other numbers.
Any suggestions on how to diffuse the light more evenly? By the way, I have to stay with LEDs because of the amperage limitations of the Tsunami decoder.
Thanks
Dave
Try a thin piece of clear acetate painted white behind the number board. Then, an LED behind that. The acetate would serve to diffuse the light.
Marlon
I have tried .010 white styrene between the LED and the number board but the light is still not distributed evenly. I have tried .020 white styrene and the light distribution is ok but only if I reduce the value of the resistors significantly to make the LEDs really bright. That presents a problem with the total amp draw when both front and rear lights and all four number boards are lit. I have no choice but to light both front and rear lights and all the number boards on the same circuit because the only two other lighting leads ( F5 and F6) will be used to control the colours of the classification lights. With the front and rear lights and four number board lights all on the same circuit I risk exceding the 100 ma limit on the circuit if the number board LEDs are drawing close to their maximum.
Hence my question. I am looking for a way to diffuse the number boards lighting without drawing too many milliamps. It also has to be done in very little space because of the size of the frame.
OK, next I want you to tell me how to make myself into a millionaire by next week![swg][(-D]
Seriously, how can I diffuse the light?
Dave
Have you tried scuffing the lens of the LED so it acts as a diffuser as well? Just an idea. Fine sandpaper would probably do the trick. Scuffing the surface of a piece of plastic between the LED and the number board might help too.
I have used plastruct clear plastic rods, rectangles, etc to make my own light pipes. So, I can use 1 LED per 2 number boards. The plastic also diffuses the light. It may take a couple of attempts, but when you get it right, you’ll know. In this case, I normally affix the LED to the body top and have it covered. I also paint the LED silver except for the point where I need to feed the light pipes and then cover with shrink tube.
Richard
Take a clear piece of plastic, sand it rough or score it hundreds of times till it’s “frosty” looking. This will turn it into a diffuser by etching it. If lighting it from the back is still uneven, try lighting it from the side.
A similar effect produced the window below.
When I started building structures in earnest a few years ago, my original source of lighting was 5mm Xmas LEDs, the ones with a cone- shaped lens under a flat top surface. I used 400 grit wet/dry paper to scuff the top and the sides translucent, so that the light would be diffused. In an open structure, just one if these, coupled to a 470ohm resistor, run on a 12VDC power source was sufficient to light the interior without glare. Nowadays- in structures and engines/cars- I use 3mm flat and round LEDs, but still scuff the LED if I feel I need less glare. You can use 400 or 600 grit wet/dry, but too high a grit number justs smooths the plastic, and too coarse (low) a grit number will scratch more than needed. You can also Dullcote a piece of clear plastic to act in concert with the sanded LED or experiment with just the coated plastic and the original LED condition. Cedarwoodron
Thanks everyone for the suggestions.
I have been trying to use flat LEDs which I think might be half the problem. Even when the lense is sanded or a diffuser is installed the light pattern is still too narrow.
I have some 3mm round LEDs so I will sand the surface of one as suggested and see how it works. There isn’t a whole lot of space between the shell and the frame so whatever I use has to be fairly thin.
Thanks
Dave
Hey Dave,
I have something a little different, maybe even a different aspect on the whole thing.
Although everyone is altering the focal lense, not many hav addressed the reflecor angle.
I have some Shallow dome (almost flat looking) 5mm LED’s that have a 180* reflector.
They are Great for structure interiors, but too big for Numberboard Lighting.
Most LED’s now have a datagram that lists the broadcast angle.
I have had ‘fair’ luck with Proto 2K styled Wedge acrylic blocks & wetted in LED’s, but nothing ever seems true edge to edge perfect, I swear I can see the source…
I have some fine metal Checkering files down to 42 LPI, & one can use a draw file to make finer LPI in testing, but I have not done that.
Just some other suggestions & thoughts…
Thanks Chad
I have found a better solution.
First, the 3mm LEDs didn’t work because their lighting is projected out the front of the lense and there simply wasn’t enough space to mount them that way.
What I have done is to mount two flat LEDs side by side and wired them in parallel. The LEDs are about 2.5mm x 3.5mm. I had tried these before by wiring them in series by soldering the + side of one to the - side of the other but there was too much space between the centers of the LEDs. That left a dark spot right in the middle of the number board. By mounting them in parallel with the contacts on the top and bottom of the assembly I was able to get the centers closer together. I filed a bit off of the sides and managed to get the centers even closer to each other. The result is that the light is relatively evenly distributed across the whole number board. I used a single 10K resistor to drop the light level down to a level that is realistic.
I also managed to solder the leads to the red/green 0606 LEDs for the classification lights. That was easier then I thought it would be[:D].
Now I have to buy some more epoxy to stick all these LEDs in place, and I have to find the patience to glue each one into place individually[|(]. That’s the part I don’t like.
Dave
Dave,
How about some photos so we can see what you did. The results must be very satisfying.
-Bob
Boards that have “clear” numbers I redo with Microscale or Shellscale decals including a white backgroud. This helps to difuse the light.
I build light boxes in the cab roof and mount the LED back about 1/4" to 3/8" from the number board. Another key is to drop the brightness of the LED with higher resistance.
Dave,
That is actually a Brilliant idea, pun intended!
Yeah that would do a nice broadcast fill indeed.
I actually promised another member a lighting experiment, & have been held up because a single LED did not illuminate a (my) dual headlight lens set, Your solution would have resolved that nicely!
It is always good sharing & discussing ideas with you, Thanks Again!!
Here are the pictures of the LEDs attached in parallel. Sorry the focus is a bit off - cheap camera.
The LEDs side by side fit the number boards quite closely. I haven’t installed one yet but a test with them held in place by hand showed good results. This is without any diffuser between the LEDs and the number board. I will try a piece of .010 white styrene to tone the light level down a bit and further diffuse the light.
Again, sorry about the poor focus.
Dave
One other idea- painting the LED face with something that diffuses the light- a flat clear lacquer or such, may also have an impact. I usually paint the rear part of t plastic with black paint to minimize light splash where I don’t want it- back into a cab area or similar, so painting to cover or diffuse unneeded light might also help. Cedarwoodron