Faux-neon Letters for Signs or Decoration

Hello! I recently made a set of neon-look letters for a large outdoor sign. Here's how I did it, using a CNC router, a design program (Adobe Illustrator), and some imagination.

Supplies

CNC router (I used an Inventables X-Carve with a one-meter-square working area)

5 meters 12V SMD2835 600 LED "flexible neon" strip light, 6 mm x 12 mm cross section, any color

extra end caps for LED strip

5 amp / 60 watt power supplies with 5.5 mm barrel connectors

2-conductor doorbell or thermostat wire

heat-shrink tubing

3/4" (19 mm) MDF

1/4" (6.35 mm) MDF

construction adhesive

hot glue

primer and paint

Step 1: Designing and Exporting the Letters

The temporary sign needed to read "FORREST" and would be located on top of a hotel porte-cochère. (I just learned that's what those overhangs over hotel entrances are called.) So, the letters needed to be big and bright. Rather than one huge sign, I chose to make individual letters, for several reasons:

Weight. Each letter is made of 1" (25 mm) total thickness of MDF, weighing maybe 15 lbs. (7 kg). A single large sign with seven letters would weigh... too much. Moreover, since I was installing it on a rooftop, a single large sign would be very awkward to handle.
Power. The combined power requirement for all seven letters would be 300-400 watts (more later on calculating this), but individual letters could be powered separately.
Reusability. In the future, I might need to spell different words or names.
Practicality. Single letters would fit on my CNC router's table.

I used Adobe Illustrator to create both the letter outlines and the neon traces at full size. The design of both the letters and the neon traces was based on the hotel's huge neon sign, which reads "TIGER". I scanned and traced the TIGER letters, then adapted them to create the other letters — "F" was just a modified "E", and a reflected half-"G" became the "O". The only letter I had to create from scratch was the "S".

I designed each letter (including space on either side) to be no more than 24" (60 cm) wide, as this is a standard width of MDP handy-panels.

Finally, I exported each letter's outline and neon traces separately as SVG files.

Step 2: Measuring for Materials and Power Requirements

Since I designed the letters at full size in Illustrator, I could use Illustrator's "Document Info" panel to determine the amount of "flex neon" LED strip lighting I would need for each letter.

Choose "Objects" in the panel's menu. Select the traces for any letter. The Document Info panel shows the total length of the paths. (You may need to adjust your unit preferences first.)

For example, the four paths comprising the "O" measured 353 cm. Adding up all the letters resulted in a total length of almost 25 meters. Since the flex neon material is usually sold in rolls of 5 meters, I would need 5 rolls in all.

The length of LED determines the power required to light each letter. According to the specs, the LED strip consumes 60-74 watts per 5 meter roll. So I would need 300-400 watts in all. At 12 volts, that's 25-35 amps in all. Individually powered, however, each letter would need about 60 watts or 5 amps. Power supplies of this size are readily and cheaply available on eBay and elsewhere.

Step 3: Cutting the Neon Traces With CNC Router

My CNC router is an Inventables X-Carve with a 1-meter-square table. To carve on this machine, you typically need to use the online Easel application. Fortunately, Easel can import SVG images. Unfortunately, it will not import SVGs created by Illustrator at the correct size and position. So, I had to go back to Illustrator and painstakingly measure each letter and locate its origin. I ended up with a list like this:

each panel 30" tall
bottom edge of traces should go 6-3/4" from bottom edge of panels
most neon traces about 19" tall
bottom edge of outlines should go 5-3/4" from bottom edge of panels
F: 24"w; traces start 3.88" from left edge; outline 2.88"
O: 24"w; traces start 1.61" from left edge; outline 0.908"
(etc. for the remaining letters)

With these numbers, I could correctly size and position each letter in Easel, as the photo shows.

I made a test trace on some scrap MDF to test the fit of the LED strip. Although the photo indicates a 1/4" bit, I switched to a 5/16" because it had a better fit with the 6mm-wide LED strip. I also modified the depth to 0.3" (~8 mm) — this seemed to work best with the strip height.

After cutting each letter into 30" x 24" x 3/4" (19 mm) MDF, I painted the panels with dark green glossy exterior grade spray paint. MDF is not waterproof, but with good paint coverage it should last much longer when used outdoors.

I also determined where each segment's power wires needed to pass through to the back of the sign. I drilled a 1/4" (6 mm) hole at about a 45-degree angle through the MDF. (The angle was intended to reduce stress at the solder joints.)

Step 4: Cutting, Wiring, and Installing the Fake Neon

This LED strip can be cut every 3" (7.6 cm); there's a faint mark on the outside of the strip that will show you where you can cut. For this project, it's better to cut short than long. Be sure to cut exactly on the mark! You should be able to see the + and – contacts on the LED strip inside the rubber covering — they will look like two silvery circles side by side at the edge of the cut. Look closely and one might be marked "+". Make a note of which one. With the strip I used, the positive contact was the one closer to the green side of the strip.

I went back to Illustrator to measure each separate path in each letter. Using the complete cut list, I tried to cut the LED strips so that each trace would made of a continuous piece of LED strip, if possible. (It was possible.)

I hot-glued a plastic cap on one end of each LED section to protect the end from water getting in. A big dab of hot glue might work even without a cap.

I'm using 2-conductor doorbell wire here, 18ga or 22ga. I cut a generous length, like 2' (60 cm), for each segment. Each conductor needs only a very short stripped length. I tinned the wires for easier soldering.

With the contacts facing up, I carefully cut away the rubber covering just on the "top" side, for access to the contacts with a soldering iron. I poked holes through a plastic end cap and threaded the wires through.

Use weights or "helping hands" to position the wires against the contact pads. Make sure the red wire goes to the contact pad identified as "+" above!

One quick touch of the soldering iron should be enough. If you tin the wires, no need to add solder. The contact pads are often pre-tinned as well. Try not to melt the rubber strip or the plastic end cap.

Squirt some hot glue into the end cap and push it on. (I had to shave a bit off the rubber cover to get the end cap to fit.) I added a piece of heatshrink and a big glob of hot glue on the outside of the end cap to finish the connection and give it a bit more strength and water resistance.

Now the fun part: Installing the neon. I started from the powered end of each strip, feeding the power wire through the hole to the back of the panel. A blob of hot glue in the channel every 6" (15 cm) or so. For the longer runs, I would glue down one section or straight run at a time, rather than trying to glue down the whole segment all at once.

Finally, I put a generous blob of hot glue over both ends of each segment, and in both ends of the hole with the power wire.

Step 5: Making the Letter Outlines With CNC Router

The letter outlines are cut from 1/4" (6 mm) MDF, using an Inventables X-Carve CNC router. Just like in Step 3, I had to adjust the position and size of each outline before making the cuts. Since these are through-cuts, I left some bridges to hold the panels together during the cut. Make sure to save the "counters" (inner parts) of letters like "O" and "R".

I painted these with several coats of brush-on white exterior latex paint. This should be done before attaching the letter outlines to the neon panels, else it would be much harder to paint the edges without dripping on the panels.

The letter outlines are glued to the neon panels with construction adhesive. I used clamps and weights for a tight, flat bond. Short staples would also have worked, but would have required filling, which I didn't feel like doing.

Step 6: Finishing

After trimming to exact height on a table saw, I painted all exposed MDF on the edges and backs of each letter.

I connected all the power wires for each letter's segments to each other, and to a female 5.5 mm power connector, making sure that all red wires were connected to each other (and same for black). The red wire(s) must connect to the + contact in the power connector! Typically the power supply will have a small diagram showing whether the center or outer conductor is the positive one. The power supplies I bought (eBay) included matching female power connectors, otherwise make sure to buy the correct kind to fit your power supply.

Finally, I built a base out of plywood, with 2 x 4s attached vertically to form a slot that will hold the panels upright. I lined it with thin carpet scraps to protect the letters' finish.

Step 7: Installation

Your installation will be different of course. My crew used a scissor lift to carry the base, letters, and power supplies to the roof. We weighed the bases with sandbags. The power supplies were plugged into a power strip, which was then connected to a timer.

It was a bit of work, but think it ended up looking great! The sign was in place for about 5 days and lit up only at night.

If you make this project, you could use any letter design, LED color, or paint colors you choose. Just be careful that your neon traces don't turn very sharp corners.