2016-09-27

Illuminated street

I describe here the steps I took to mount the BUSCH HO 2878 backdrop on my layout with two sets of lights, the windows and the streetlights. Here is the finished product so one can see the end result that I was aiming for...

During the day:

With streetlights


and with lights on in the buildings:



So how did I get from two pieces of paper to that....  well first I raided the kitchen and took a length of cookie tray paper (parchment) to use as tracing paper.
I then traced the outline of the buildings, windows and street lamps onto the tracing paper using a marker.

I decided to make the support out of a sheet of 3/4" Styrofoam™. I pinned the tracing onto the Styrofoam and cut the windows out using a sharp work knife.


My intention was to place individual LED lights behind each hole and to minimize the number of LEDs. I decided to combine some windows into a single hole in the Styrofoam (as can be seen in the foreground above).

I then tested the backdrop over some holes but found that the black ink on the back was not enough to prevent light from shining through!


So, I decided to mask off the edges of the windows using black insulation tape.

I drilled 3mm holes for each street light lamp (two lamps per pole)


At this stage two things happened, I decided that using a single strip of LED lights behind the Styrofoam would be much easier and cleaner to wire up than individual lights in every window hole. While testing a roll of LED lights I also left the roll of LEDs sitting on the Styrofoam board. The 24W of electricity melted the Styrofoam and as luck would have it, it was on the front surface - so I had to abandon the Styrofoam board and start again.

I then decided to use thinner foamboard (1/4") and cut each window individually. I went to Walmart and found a board used for school project presentations - a sandwich of paper and 1/4" foam. Using a new sheet of tracing paper I traced the windows and cut them out one by one. Since I now knew that light would shine though everywhere I also marked places where bushes partially obscured a window. I skipped windows that had lots of vegetation in front of them or a streetlight.


The paper covering of the board is not ideal. It leaves little tufts of paper especially in the holes drilled for the streetlights:


Since the presentation board was only 4' long, I had to join two pieces together. Not a problem as I could use the straight edges together to make a good seam. I decided to use the folds of the board to allow the two ends to slope back towards the rear, adding some 3D effect to the row of houses running down the boulevard. I taped the seam on the back with black insulation tape too.

Once I had cut out all the windows and drilled the street light holes I tested by laying it over an LED strip.


The overlap of the two paper backdrops doubled up on a window - meaning that half the window would have two pieces of paper over it. I sliced off part of the left backdrop so that there was no overlap on the window.

Now a big step, I had to glue the backdrop onto the cut mounting board. Once glued down there was no going back or changing anything. In order to keep it properly registered I pinned it to the foamboard in the sky and then sprayed the board with 3M aerosol adhesive. The paper was then carefully rolled back down onto the glued board.


 The right hand panel that had to overlap the left panel was pinned in one corner so that it could be rolled down after the left panel was down.


Once glued onto the board, I cut the sky and the board below off together along the skyline. Very small chimneys or details were cut off.

I could now try a test fitting on the blue wall of sky:


I noticed how the white edge of the foamboard could be seen so I painted the edges in colors that matched the roof.

Now I had to make a 'frame' around the edge to keep the light in the 'box'. I placed the tracing paper on the back and drew in a frame.


I then placed that tracing paper onto the original Styrofoam board and cut out a frame:


I painted the inside edge of the pink frame white so that I did not produce any pink reflection.

I then used the tracing paper to mark off the area on the wall where I wanted to mount the row of buildings. This was so that I could paint it white to reflect light back out the windows. Some areas were painted yellow to add variation to the color temperature of the reflected light.
I also drilled some air holes to let out the 5W of heat generated by all the LEDs.



Now it was time to add some lights! I soldered two leads onto the LED strip:


and pasted it onto the back of the foamboard. Yes, the lights shine back towards the sky and are reflected off the rear wall through the windows.

In case the sticky backing of the LED strip  fails after time, I also added some wood glue in places that did not have open contacts:


I snaked the LED strip along between the windows about half way up.

The LED strip that I used consumes 273mA of current at 12 Volts.

I then inserted white LEDs into the holes behind each streetlight lamp. Each pair was connected in series with a 240 Ohm resistor. I inserted the legs of the resistors into the Styrofoam to hold them in the air for best heat dissipation. Each pair was daisy chained to the next.
A single 1N4004 diode was added to ensure that an incorrect wiring would not destroy all the LEDs. This brings my 12.2 Volt supply down by about .56 Volts and results in a 11mA current in each LED.



At last I could now place the street onto the wall to see how it would look. Some of the windows were a bit too yellow so I put some white paint over the yellow.
The two circuits were connected to a Märklin  K84 module and I created some events in my software to switch the windows and streetlights on and off.


I then glued the frame to the rear wall and wedged heavy objects between the first attempt Styrofoam and a strip of wood screwed to the layout.


The next morning I removed the weights and could see how it turned out.