DIY Blacklighting
by Brennen Dyer
Running a light at night is a great way to find insects and modern LED tech is making it easier than ever. LEDs are durable, efficient, and easy to source. After cobbling together horrible LED setups for years I finally have some designs that I'm proud of. This is what I use on my collecting trips.
There's often a mix of entomology folk wisdom and science surrounding the use of certain collecting techniques. My goal for lighting should be to emit in the visual spectrum of most insects and do it as brightly as possible. It sounds kind of dumb, I know, but LEDs are new and I feel like many entomologists haven't given the tech a complete look yet. These light strips emit the same UV wavelengths as the mercury in more familiar light sources so I think everyone should give them a try.
Now, why not just buy an
Entolight
or
LepiLED? I've had one of each in hand and they're great lights. I just want to run mine off either 12V or 5V, make them attach to traps and accessories of my design, and keep learning how to work with LED strips.
The light strips
My local sources are hardware stores. But to get LED strips and lots of connectors I recommend LEDsupply and Waveform Lighting. Depending on your specific needs, such as wavelength or waterproof strip, you may need to shop around. My local hardware store has the PVC pipe and most of the fittings I need. A PVC pipe cutter makes it much easier to make these things. It's easy to wire things for this because it's just a 2.1mm barrel connector. Parts are everywhere.
The strips of 365nm UV from Waveform came with a plug on both ends which is nice. For simplicity I ordered a full 16.4' (5m) roll and used half of the roll to make each light, one for each side of the sheet. For portable traps I used only a meter long strip so I could power it all night with a small 12V battery or even a USB powerbank, with the right adapter.
All I did was wrap the strips around 1" PVC pipe and left a few inches exposed at both ends. A coupler on the end near the plug is great for securing the cord and as a mount for a clip or stand. It's super cheap and easy to make.
Once I got my hands on ridiculously big heat shrink tubing I immediately starting covering all the lights I have. Although I ran lights all night in the rain in Arizona without an issue, I want it to keep the LEDs safer in general. A little silicone where the power cable comes out will make it pretty much waterproof.
I like to make these hangers out of an end cap with eye hook and bit of pipe sticking out. It packs well and lets me still use the light on a stand or in a trap. Once you have something this simple, just go to the hardware store and start fitting stuff together. Design whatever works for what you have.
Power draw
Depending on the power source it can pay to find out how many amps the DIY setup draws. For my USB 5V to 12V converter for example, it's limited to 1.5 amps of 12V. Any good website will list the specifications but I want to verify if I have the tools. I don't want to accidentally run down my battery too much because I didn't check my math. Car batteries are expensive and are damaged by draining too far.
I have a pair of 2.5 meter long (half a roll) 365 and 395nm lights and they almost draw the same amount with 395nm 1.6 amps and 365nm at 1.8. It's not a huge difference but it might matter in the long run. The math to decide what size battery is needed is simple. Multiply amps drawn by how many hours it will be on, double it if you're using lead acid, and search for a battery with that many amp hours. For my 1.8A light to run overnight for 10 hours, it'll use 18Ah so I should use my 35Ah battery. But to run both lights I should have double that still.
Or just get a generator.
This USB converter from LED supply pulls 1.6A with this 1m strip of 365nm. My 26000mAh powerbank can almost power it through the night. Good enough for a single night I suppose but it takes all day to charge.
Blacklight sheet
The sheet setup I made is pretty simple. I tend to camp in forests so I hang paracord between trees or vehicles. I use a cheap white bed sheet with paracord clipped to grommets I put in it. Some people use photography backdrop frames in areas that don't have trees. You could also just lay the sheet on your vehicle or even the ground. I've used little stands made of PVC to hold my lights above a sheet that's flat on the ground. For blacklighting, the sheet is there to help you see the insects, it's the lights that bring them in. So don't get hung up on having a vertical sheet. Besides, what comes in will be the result of location and timing as much as anything else. Some of my best specimens were caught with my worst equipment.
Bucket trap
My local hardware store had most of what I needed for this project, however I had to order a pack of 1/2" 5-way crosses from ebay since it's not a real plumbing part. The full parts list is below. I used a 2 gallon bucket for its size and it worked out very well. You can use fluid, like high proof alcohol, or fumigants.
- 2.75" of 1/2" PVC pipe, x4
- 1/2" end cap, x4
- 1/2" 5-way cross, x1
- 7" of 1/2" PVC pipe, x1
- 1" to 1/2" reducer, x1
- 10" by 3.5" piece of sturdy plastic, x4
- Tight grip sign holder, x8
- VHB tape
I got very lucky when I found out that PVC vertical blinds are perfect vanes for a 2 gallon bucket. They're 3.5" across and easy to cut while being fairly sturdy. I found mine in a dumpster but you can buy new replacements. The sign holders are from a random ebay listing. I have a USB converter for when I want to use a powerbank, but I prefer to use 12V because it's more efficient.
All this could be built for maybe $150 but that's a very rough estimate. Between dumpster diving and not paying attention while prototyping bits I don't have the receipts. But for planning purposes you could easily get that cost down at scale, however the biggest single cost is the LED strip. Ordering longer strips and soldering connectors is the most economical way of making a set of these.
A few ways this could be improved is with a nicely fitting funnel. That would reduce evaporation of alcohol but isn't strictly necessary. It could be adapted to being hoisted up if I wanted to do canopy trapping.