Project Halloween UV Light Bomb Evolution

It’s the middle of August and that means the stress is starting to build fast. We are around 8 weeks before our annual Halloween Party and a big element of that event is the haunted trail (link here). The Haunt Factory lights are on and the machines are already running double shifts. We try to bring you a lot of our Halloween project, although due to the time crunch those usually come after the haunt. As I just finished the latest design for our Halloween Prop UV Light Bombs, l thought it would be a good time to feature them while the details were still fresh in my mind.

These UV lights have gone through several iterations over the years. I’ve never been happy at the price point of these units and each iteration was focused on trying to get the components as cheap as possible and still deliver the effect we wanted. Our first version was actually born out of a need to put some light on areas that required extra caution by our guests, a dip in the ground, a step up, maybe a low hanging branch. The safety of our guests is priority one. Scares are a distant second.

Hit the jump to learn how we have evolved the design our of our haunt lights over the years.

After a few hours in the PVC aisle, I came up with this initial design.

It is based around a large white light LED with a PVC shell. I rely heavily on my 3D printers for a wide range of haunt needs, so you will see that utilized in a number of areas in all my projects. It was critical there was a button option to turn it on and off so we could quickly power them down at the end of the night – it is well into the morning hours when we start closing the trail – taking batteries out is the last thing we want to do when we are already exhausted. 9 volts are the primary battery source for our prop controllers. The dimension of that battery had to be accommodated in the PVC shell. The best diameter seemed to be 1 1/2 diameter. Found a tee connector that had a 3/4 inch port which was perfect for a switch.

Having that dimension for the entire shell was overkill, so that brought with it two reducers – one for the 1/2 neck and then another reducer to accept a 1/2 pipe at the bottom that we can stick into the ground. So, a 1/2 90 degree connector, 1/2 pipe, the 1 1/2 connector and then two reducers. The reducers are ridiculously priced and that tee wasn’t cheap either. Printed up some inserts for both the light and the button so it fit into the connector ports.

Now we get to evolution number 2. With the caution lights out of the way, the next step was to make what I call UV Bombs – Think Blade comic book. Basically an array of UV lights that will make UV sensitive items pop out in the woods. I’ve seen a number of these online and they either require them to be plugged in or won’t last through the night. I already had hundreds of UV LEDs leftover from other projects and decided 4 of them per light was a nice trade off of battery life and brightness. UV lighting isn’t like white lighting as you are not so much trying to illuminate the prop, rather have it glow in response to the UV waves.

The small 1/2 90 degree connector was not big enough to accommodate the 4 LEDs, so had to rethink that part. Found a strange connector with 2 x 3/4 ports and a 1 inch port. That allowed me to move the switch behind the lights. Decided to keep the battery housing configuration and only due to having them around already, used the same tees as in the first version.

The reducer at the neck had to be upped to a 3/4 along with the pipe. We tend to use 1/2 for our stakes, so that reducer stayed the same. Needless to say, this configuration was even more expensive than the first – was going the wrong way on the price point.

While looking at this configuration a year later, it was pretty easy to figure out how to save some costs – the tee was not needed with the new light housing connector. That side was left open which completely eliminated the waterproof design I was going for (yes, I could have put a plug in it.. but more cents would be added).

Did some quick tests realized that a 9V battery can actually fit into 1 1/4″ diameter pipe allowing me to shrink the connector – translated … CHEAPER. Picked up a basic 1 1/4 coupler, an end cap and pipe to connect the two. Now needed a 1 1/4 to 3/4 reducer for the top side and not shown in the picture, but grabbed a 1/2 cap I just screwed to the bottom of the 1 1/4 cap to hold the 1/2 stake.

Still seemed like a lot of parts and that translates to cost. Went back to the PVC aisle at Menards to come up with a new plan. After trying combination after combination I was about to give up as I couldn’t figure out a way that didn’t INCREASE the cost. Whenever a reducer got involved, the cost went bonkers. Bummed until I saw a bag full of this 1 1/2 connector. Again, no idea what practical use it has, but this had the two ports I needed – one for light and one for the button and then a down port to stake. Now get this this – the bag was $1`6.99 or $1.70 a piece – now that is a price point I can live with – it was even cheaper than one reducer.

Found a cap they had there that I doubt was for S40 pressure – likely just to cover the end when pushing the pipe through the mud as there was a more expensive cap right next it. I did have to create a new 3D model to upsize my button and LED inserts to address the new diameter of connector.

As my standard practice, I always switch the positive side of the battery. I have gotten lazy as of late and been buying my locking pushbuttons with the leads already soldered on. This always causing confusion later on, they use different colors for the same lead – I prefer red and red as all I am doing is breaking the positive connection – oh well, I can adapt since it is saving me solder time.

With the 9 volt battery connector soldered onto the button lead, the button sub-assembly could be pressed into the connector.

When it comes to projects, I always follow Henry Ford’s lead and mass produce by phase. Note, button colors are irrelevant for this design.

Now time to work on the LEDS. We put our LEDs in parallel so we need to account for the extra voltage across each LED. As a rough calculation our LEDs drop 3V and have a forward current of 20mA (your LED may very), using Ohms Law of V=IR or R = V/I, you get (9V-3V)/20mA) or 300K. We tend to run our LEDs a bit hot so we use 200K resistors, but you should follow the LED manufactures specs if you are unsure of the impact that will have on your light choices. For ease I connect the resistor directly to the positive (long) lead on the LED and then put another lead wire on the other end of that.

We never know weather conditions we are going to get the night of the event and want our products to be built as solid and dependable as possible. All connections are shrinkwrapped. In this case the wrap has to cover the LED lead, the resistor and the lead connection. Again, complete this phase on all the LEDS needed for this project (10 lights x 4 LEDs per unit).

The negative just needs a lead added to it.

Our early models experienced a number of failures at the resistor connection – the tiny wires would break if handled too rough. Additional emphasis was added to make that more industrial strength. The wrap for the negative lead was put around the positive lead as well – either directly with one wrap over both, or if it was wrapped individually, another piece of wrap was put over the two locking them together – never had a failure since.

As you probably expected, that was done to all 40 LEDS.

Grabbed a newly printed LED holder and inserted 4 LEDs into each one. The hole diameter provided a tight fit, but went ahead and added some glue on the back of each one to make sure they stayed in …and added an extra moisture seal. Each set of 4 had their positives and negatives combined and tied together.

The LED set of 4 positives was connected to the other lead of the switch – this is where you can get confused as you are actually connecting a black wire to the positive LEDs – if it helps you can tie the black one to the battery connector and then the red to the LEDs – either way, there is going to be a black tied to a red somewhere which doesn’t happen in the ones I build.

The negative of the battery is then soldered onto the negative leads of the LEDs and the connection shrinkwrapped. Once that is done, simply slip the LED holder into the port opposite the button.

All the wiring is completed now. Only thing left is to add the stake. For ease, we just took a 1/2 pipe cap and screwed it to the bottom of the 1 1/2 pipe cap using a lock nut on the 1/2 side to keep it solid against the cap. Grabbed some 1/2 pipe, cut some 10″” lengths and angled the ground end to make it easier to stick in the ground.

Cut a small piece of 1 1/2 pipe to affix the stake to the body of the light and we have ourselves the latest version of the UV light bombs. Cheapest version by far and no expensive connectors or reducers in the design.

Now you have a directional UV light you can point at your props to make them pop in the dark night.

Just some examples of what to expect with these UV spot lights. Here is a one of our dragon props light by a standard white light.

Now, this is what it looks like when you replace that white light with one of our UV units – best of all, you can’t see the rays, so it looks like it is just glowing on its own.

Here is a quick shot of a portion of our cemetery.

Add some UV lights pointed at the white of the tombstones and you have yourself a setting sure to put a scare into your guests.

Lastly, if you happen to use UV reactive paint or fluids in your props – you can really make them pop. Standard looking needle vials during the day.

Deadly glowing poison at night as the UV fluids react to the “black” lights pointed at them.

Need to call it a post here – hope you enjoyed a walkthrough of one of our favorite lighting effects on the haunted trail. Stay calm, make a run to your local PVC store and scare on!!