This Halloween tombstone project uses glow in the dark lettering and UV LEDs to light it up! In addition, the LEDs fold away for flat storage off-season. The lettering is much easier to do using glow in the dark hot melt glue.

I had been using CFL black lights to light these up, but the LEDs don't require having fragile lamps out in the yard. I tried this with the LEDs right on the edge of the tombstone, but the UV did much better with them farther away. Putting them on a fixed structure would work, but this approach with hinged LED "wings" allows them to be flat stacked for storage.

Step 1: Parts

There are many great Instructables on making tombstones. For these, I used:

Foam Sheet - 1.5" thick rigid foam insulation
Grey, White, and Green spray paint, but you can brush these too.

For the UV part:

5050 UV LEDs - I used epoxy coated IP65 ones, but they are slightly more difficult to solder to than the non-waterproof or silicone jacketed ones (IP67).
12v batteries for cordless or 12v power supplies for wired. This one comes with the below connector.
2.1mm x 5.5mm DC Power Connector Female - this is a standard 12v connector that you can screw the wires in to.
Glow in the dark hot melt glue sticks - these only come in the mini size, so I also had to get a mini hot melt glue gun

Hinges - 2 per tombstone. I used a pack of inexpensive 2" hinges.
I used fairly rigid 22 gauge stranded wire like this, but silicone wire is generally nice for LEDs since it tends to tear the copper foil pads off less - I used red and black to keep the polarity straight - other types would be OK too.
8mm heat shrink tubing
regular hot melt glue and glue gun
foam core sheets
black spray paint
4" cable ties

Step 2: Tombstone

Tombstone

I won't spend too much time on the tombstones themselves since there are many Instructables on that. I used 1.5" rigid foam insulation, which worked well, but is a bit brittle.

For the detail and writing, you can just use a permanent marker for now since we will be going over that with the glow in the dark hot melt glue. I tried using glow in the dark paint, and it works, but it takes several carefully painted layers where you try to build up a bead with a small brush. The hot melt glue is much easier to do. I outlined the tombstone with the glue too since the edges were not as easy to see when lit up.

Note: the ones in the pictures were made in a previous year and the detail was carved in. I have now added glow in the dark hot melt glue on all the details and writing, as well as the bead around the outside edge.

LED "Wings"

I had originally thought I would just surround the tombstone edge with LEDs, but the LEDs work much better if they are a few inches away. So, I came up with this approach, including the hinges to make it easier to store. I do not think having them only on the bottom would be sufficient, but that is a possibility. Fortunately, it does not take very many LEDs to light up the tombstone.

Cut a hinge-width (1.75") cross piece of foam core that is 10" longer than the width of the tombstone. That will allow 5" on each side for the LED parts. The second piece of foam core has a 1/2" strip on the edge to hold the LEDs, and a 4.5" hinge width piece to connect to the end of the long strip. See the pictures for more detail. The LED holders end up being a kind of "T" shape, and I offset the hinge part so I could cut them out of one foam core rectangle. Since the hinge part was offset, I mounted the cross piece strip a bit lower of higher - used the LED parts of the foam core to get the positioning right.

Once the foam core parts are ready, use regular hot melt glue to glue the main cross piece to the tombstone. Check the fit of the wings, and trim the LED parts as needed so they fit nicely when folded. Then, glue one side of the hinge to each LED holder. Then glue that to the cross piece so they line up nicely. Make sure to open the hinges immediately so they do not get glued shut. I used extra glue to to hold them in place better.

Once those wings are complete, use flat spray paint to make them black - being careful not to paint the tombstone front.

Step 3: Wiring

The 5050 UV LEDs are very bright. I did try some 3528 LEDs, and they are OK, but dimmer. They use 1/3 the power too. For the 5050 LEDs, having "wings" with 21 LEDs each would use 42 total (I had some tombstones that used fewer LEDs), and draw about 0.84 amps, or just over 10 watts. They use 6 amps for 300 LEDs, and run on 12 volts.

Since the 5050 LEDs are analog, you can power them in parallel. Once the paint is dry on the wings, you can measure how much wire you will need to solder to the strips. The wire will need to run behind the LED wing, around the hinge, and down the back of the tombstone. I used the LEDs that are "waterproof" - epoxy coated (IP65), so I had to carefully cut the epoxy away from the solder pads on one end with an X-Acto knife. Using the non-waterproof ones or silicone jacketed ones (IP67) would probably be a bit easier.

Solder one red wire to the "+" and one black wire to the "-" connectors on either end of the strips. Use a piece of 8mm heat shrink to protect the end. For more waterproofing, use some silicone caulk to seal the ends.

Attach the LED strips to the wings with the self adhesive on the back.

Then run the wires behind the wing, around the hinge and to the back of the tombstone. I used hot melt to tack these on the way, and had to wait for each part to dry before moving on.

I also used some 4" cable ties to hold the LED strips securely to the wings.

You should now have two sets of wires on the back. Combine the red wires and srew them into the 2.1x5.1mm power connector terminal.

You should now be all set to run with a 12 wall adapter or battery.

Happy Halloween!