Back Lighting

[munzieb]

Thinking about back lighting my logo project with plexi glas and LED lighting. Has anyone tried this and how does it look?

[Jim McDonald]

LEDs work very well to edge light plexi.  Think mounting them in the bottom of the stand.

[CharleyL]

Plexi transmits light through it very well from edge to edge or face side to face side, but the light doesn't come out of it at 90 degrees from the source light very well, unless you engrave or somehow interfere with the smooth surface in some way. Sand blasting will produce a frosted surface and a nice even face light when used to back light an image, but clear plexi will not provide much light if the face is smooth.. Most of the light that goes into one edge will just go through the plexi and out the opposite edge. Letters or images engraved into the surface will  light up brightly, but the rest of the light will just pass through the plexi to the opposite edge.. Just keep this in mind when planning your project. A few simple experiments with some scrap plexi and a flashlight to provide the edge lighting will give you a better idea of what I am talking about.  

Charley

Edited May 25, 2017 by CharleyL

[munzieb]

Great information. I have some scraps of Plexi glas and will give it a try once I'm done with my plaque cutting.

[CharleyL]

You can even bend light around corners if you make radiused (not right angle) one piece curves with the plexi. It's a great learning experience. Light will come out of the face surfaces, but most of it will stay inside as long as the surfaces are smooth.Engravings will light up brightly because you are interrupting the light path and it will come out of that altered area.

Have fun with it.

Charley

Edited May 25, 2017 by CharleyL

[munzieb]

Thanks Charley, Almost done with the cutting and looking forward to doing some experimenting. Will sanding in those exposed areas work? Most Led strips are 1/4" wide and I cut the plaque 12" wide because there are some strips available that size. Can I double up the Plexi Glas (typically 1/8") or look for wider material? Should I back up with 1/8" BB or just apply a dark or reflective coating for best effect? Lots of questions, just have to start experimenting until I find a "light bulb" like Edison, that works. Ah!,  tungsten, Who would have thunk!

[CharleyL]

You will need to experiment with textures and lighting. As far as where to locate the LEDs, I think you will get the best results lighting the edges of the plexi, so mount the LEDs to shine into the edge of the plexi. If you want the whole panel to light up evenly LEDs all the way around the piece to shine the light in from all 4 edges may be best. Again, you will need to experiment. If you want the whole surface to light up, frosting the surface by sand blasting will do it. A mirrored or bright white surface behind the plexi will brighten it. A random orbit sander on low speed with fine grit sand paper may work if you don't have access to a sand blaster. Again, experiment. 

I design and build exhibits for the  NC Science Museums, mostly for the one closest to me in Charlotte, NC. www.discoveryplace.org. When building these exhibits I do everything needed except for the graphic arts work. They have whole departments to do that part. I do the cabinet making, hydraulics, pneumatics, mechanical, wiring, programming, etc. . Many of these exhibits involve researching materials and techniques, like you are doing, to find what works the best for the project. I frequently get involved in combining materials to produce the effect that they are looking for, much like you are doing. I've always enjoyed doing this part of the job and have learned a lot about the science of lighting effects and other things  in the process of doing this research,. I'm a retired automation engineer (EE), so creating new machinery is something that I have done my whole working life. Mostly, I've done the control systems part, while others in my team did the rest. The actual work part of this was always fun and an interesting challenge for me, so doing it for the Science Museums gives me some more challenges and fun now that I'm fully retired (I  have now retired 5 times, but new offers and higher pay have kept pulling me back to work - I do the museum work for free as a volunteer and get reimbursed for materials and mileage. Although there are schedules to keep, I rarely need to work more than a couple of days per week.

 

Two years ago I was given the task of creating an indoor thunderstorm (sound, flashing lights, and rain) for a rather large young children's exhibit. It took a lot of research to make it appear as real as possible, yet avoid high voltage and other safety concerns. We also couldn't use strobe lights because that kind of flash can cause seisures in some challenged children.. A lot of research and experimenting was required to make it work. 

We ended up with a painted Styrofoam cloud attached to the ceiling with many tiny holes in it so the water that comes out is formed into droplets. A pump and reservoir tank hidden inside the exhibit provides the rain water.. A pipe runs from the pump, up through the wall, and above the ceiling to the cloud. A bright daylight colored floodlight is hidden below, but in a dry spot. It is flashed at the cloud to simulate the lightning and digital audio of thunder is played through hidden speakers, also in dry areas. There are 12 different thunder storms of varying lengths and intensity, all controlled by an industrial PLC (a kind of PC designed to operate machinery) The audio unit is a computer .wav  file player that plays different .wav audio files on a photography type flash style memory card. Each audio file is activated by the PLC and a different storm plays each time the button is pressed, up to the 12th storm and then the sequence starts over again. Th button causes the storm sequence to start and the system is designed to ignore additional button presses until the storm being played comes to an end, plus a 15 second quiet time. Then it will begin playing the next thunderstorm the next time that the button is pressed. Under the cloud is a large simulated hill with Astro Turf  on the top of it. The rain falls on the Astro Turf and a tray hidden below catches the rain, which then runs down a 6" wide water fall and into a level stream bed 18" above the floor. The kids can safely play in this water and add little stick dams between the rocks to divert the water in different directions. The water level in the stream never gets more than about 1/2" deep, because there are hidden drains in the edges of the stream bed. At the end of this stream there is a larger simulated rock with a big main drain. The rain reservoir and the pumps are hidden under the stream bed and the water is replaced daily with fresh city water to minimize contamination problems.  

 

About 10 years ago we were doing an Astronomy multi  exhibit project  For one of the exhibits in this project,they wanted to somehow show a slow motion simulation of light rays traveling from the Sun, Moon, and Stars toward Earth.This one took a lot of work for the small benefit that it produced. Many kids would push the button, but not look up to see what was happening.  A start button caused tiny white lights to flash in sequence like a theater marque, but with only a few lights lit at a time. This string of lights was mounted to electrical conduit that was bent in a wavy shape and attached to the ceiling between the models of the Sun, Moon, and a Star toward the model of the Earth, so the effect was moving light toward the Earth. Since the distance between the Sun and Star to the Earth was greater, it took much longer for the flashing lights to reach the Earth than it did from the moon. I spent a lot of time in a high lift putting those conduits with the little lights on them up on the 18' ceiling of the museum. Again, the whole exhibit was controlled by a PLC. 

I enjoy making exhibits for them because it gives me many chances to kind of "think outside the box" and come up with something  safe, reasonably priced, and always very unusua,l to demonstrate to children and adults some piece of Science in a way that makes it easy for them to understand. I do many of the sub-assemblies for these projects in my home shop and then go to their shop and work with their team to finish the project, or build I the whole exhibit in my own shop, if it's small enough to do this way. I also enjoy making things that educate kids and make them happy.

 

Charley

[munzieb]

Charley, Send me the links, Send me the links, Send me the links.  I was only looking at a simple project as a gift but I am blown away on what you have done. This is a whole lot more interesting. I am amazed on what you accomplished!!!!

[CharleyL]

The Links to what? The Discovery Place link is in the top part of my last post, first line of second paragraph. They don't want me posting pictures of what I do for them, so I can't do that, but here is a photo of a concept drawing for an oceanographic submarine that I designed the electrical for. The submarine never goes under water, but the lighting effects in the room provide ripple shadows like you would see if under water in a clear lake with a bright Sun above. It's just a bunch of wavy shadows that move. (I had nothing to do with the room lighting). The sub is in one room of a satellite branch  museum of the Discovery Place Museum. It's called Discovery Place Kids and is geared to children in the 3-8 year old range. The sub just sits on the floor and has a wide door in the tail end, so kids in wheelchairs can enter it. There are electrical panels on both sides of the sub walls, A bunch of pipe and valves on part of the left side wall, and across from it a kind of simulated sonar panel with lights, switches, and sonar ping  and return sound effects. Behind the valves there are sounds of rushing water, bubbles, and gurgles. The front of the sub has a large dome window and there is a driver's console with handles, switches, and a go-kart steering wheel. Pushing one of the buttons changes the lighting ioutside the front of the sub to a black light as long as you hold the button in. Rocks and shells on the floor in front of the sub have been painted with paint that glows in the black light. The two propellers, one on each side of the door, are actually large muffin fans, and the levers on the driver's console operate them. They have screens over them to keep tiny fingers out. There are many switches and lights in this sub. Most switches don't actually do anything except turn on other lights, but the effect is good, and the kids have a great time imagining that they are under water.

I would attach a concept drawing, but this website doesn't seem to be allowing me to do this right now.

 

Charley

 

 

[munzieb]

Checked out the link and it looks like an amazing place. Lots to see and do. I'll have to visit the next time I'm in Charlotte.

[amazingkevin]

kewl

[CharleyL]

There are actually 4 of these museums in the Charlotte area. Discovery Place is on Tryon St. right in the middle of downtown Charlotte. The Nature Museum is just SE of downtown, then there is a Discovery Place Kids museum in Cornelius, which is about 10 miles North of Charlotte on an exit off  I-77 and another one now in Rockingham which is East of Charlotte about 20 miles. All of these are managed by the main Discovery Place in downtown Charlotte. The main Discovery place has exhibits for adults as well as kids. The others are more geared to young children 4-12 years old, but are still quite interesting for adults to see, but we are too big to participate in much of it.  

One of the large exhibit halls of Discovery Place holds traveling exhibits that move every few months to other museums around the country, Several years ago they had the Dead Sea Scrolls exhibit where actual pieces of the Dead Sea Scrolls was on display. 

Another was about movie making. It had about a dozen movie sets and members of the group touring got to play characters in the movie, which was video recorded. At the end of this tour the short movie there was a showing room where they got to see the movie that they just made and everyone was given a DVD copy of the movie for them to take home. My Daughter-In-Law and Grand Daughter went through this and I have a copy of the movie that they are in.  Another great traveling exhibit was about the human body. It had displays of many body parts with explanations of each and included some actual whole bodies with the skin and fat removed so you could see everything inside the body. These were all preserved somehow and encased in plastic. 

There is a whole room in the Nature Museum that I was quite involved in. It's called "Our Big Backyard" and this is the location of the Thunder storm that I created. There are also several other exhibits in there that I designed and built the controls for. The Nature Museum has an octagon shaped greenhouse attached where they have many plants and butterflies. Since butterflies don't live as butterflies very long, they are constantly hatching new batches of them. Wear a bright colored shirt in there and many will land on you. They also have live small animals in the room next to the greenhouse. A de-scented skunk, raccoon, ground hog, possum. crow, etc. live there. All of them have had some physical sort of problem that prevented them from being released back into the wild, so they are living their lives out entertaining the children.  

Discovery Place Kids in Cornelius has many small rooms or areas, with kind of  a small town theme. There is a grocery store, bank, fire house (with a real fire truck), ambulance, farm (with a real tractor), a deli restaurant, theater, pet hospital , a brick factory with an overhead crane, an airport, grandma's attic, etc. Each is geared to children's size and allows hands-on participation. There's also a Grand National race car and a speed boat with picture murals on the wall behind them, so the parents can take pictures of the kids driving them that will look quite real. 

 

We're getting way off the subject of scroll sawing, so I don't think that I should continue this here and I'm going to end it. If you have any further questions on this subject,, please send me a PM.

Charley

 

 

[munzieb]

Charley, getting off track is ok, especially when the topic is so interesting. Taking an occasional side road will lead you to some amazing places you never thought existed!

[CharleyL]

Here is a sketch photo of the oceanographic submarine that I did the electrical controls and some of the assembly work for. I tried to post it in my previous post, but the site or the internet was having problems and wouldn't accept it. Today everything worked fine. 

 

Charley

[munzieb]

That looks really neat.