Explosion Proof Lights
Some time back I found a pair of very heavy explosion proof bulkhead lights in my usual scrapyard. These were filed under the massive pile of projects to do for some time until I found some good LED kits.
You will find reference under some of the other projects on this site to ‘Big Clive’ kits and PCBs. ‘Big Clive’ supplies a kit for a really good RGB LED controller as well as bare PCBs in a number of styles- these are cheap, good quality and well thought out items, so I have made use of them in a number of projects.
Big Clive kits from other projects
I started by stripping down the lamp units and thoroughly cleaning them of years of accumulated dirt. To fit the LED parts in, I had to make a couple of modifications- the main one being to remove ceramic feed-throughs from the junction box to the main light chamber so that wiring could pass through.
The two RGB LED boards were assembled, as was the control board. The control board was mounted in a diecast aluminium box, painted black and provided with a pair of connectors- a 3 pole XLR plug for power input and 5 pole XLR for RGB output. The system is set to operate at 12V as power supplies for this are simple.
The RGB boards were mounted using some salvaged stand-offs to a scrap piece of aluminium, along with a small terminal block. This assembly in turn is bolted into the casting using the existing screw holes from where I removed the original lampholder. The wiring is then fed out through a brass gland. Connections are made via 4 core cable I laid up, connected with 5 pin XLR connectors.
Finished Lamp Assembly
Internal view of battery pack
This project was built to provide an even, bright waterproof floodlight to use for cave photography. It had to be waterproof and robust to suit being dragged through a cave, be bright as practical and give a good colour rendering.
I based the project on a Underwater Kinetics dry box with a clear lid. These are made of polycarbonate, so are very robust , and using one to house my camera on multiple trips into various caves has proven out it’s durability. The only foreseeable issue is that polycarbonate is not very scratch resistant as proven out by the state of my Nalgene bottle over the past few caving trips.
The main LED board was one of the Big Clive kits (see links page). This meant I was able to have a robust board, of a size which fitted neatly into the box (very handy) for a few pounds- no need to start from scratch. The board was populated with 45 white superflux LEDs bought thorough ebay, with a brightness of 3000mcd each, resulting in a 135000mcd total. Choosing these does not make a super-bright lamp, but enables me to prove out the concept cheaply, requires no further optics, and doesn’t need lots of cooling. If all works out well, I will upgrade to brighter LEDs later.
On one side of the box is mounted an aluminium strip ¼” thick, tapped to take a camera tripod mount, so the light can be set up on its own. On the end of the box is mounted a waterproof toggle switch and cover. The cover means that the light can’t be accidently turned on in the caving bag. Where the switch and the bolts for the plate penetrate the case, I have used a generous amount of silicone sealant to ensure a good seal.
The last major item is the battery- this is made up of 2 6V, 2600 mAh Nimh battery packs, bought from Modelpower. Although I could have used a lower operating voltage and chosen the LED dropper resistors differently, I wanted to be able to use the batteries elsewhere or for a future upgrade. Modelpower sell all the connectors so I was able to make up a neat loom to series the batteries together and to connect them through the switch and to the board. Charging is relatively easy as the lid of the box can be opened and the battery packs removed.
The batteries and main LED board are held in place with some high density foam, shaped to fit suitably.
The sort of images I have been able to capture have been like this. More photos are available on my Flickr pages. Underground Images
Gour Pool In Jugholes, Peak District
LED UV light