Resurrecting a 15" fluorescent trouble light as an LED trouble light.

[phreich]

Hi,

I just completed a fun project where I resurrected a T8 15" fluorescent trouble light that had been damaged by being left out in the rain which ruined the switch and the transformer. I was going to recycle the light at the local Free Geek (a non-profit that responsibly recycles electronics and re-purposes computers that local corporations have written off and upgraded by refurbishing them and giving them to other non-profits and needy local families.), but found an item being sold on Ebay that I realized would work to relamp this light with LEDs.

Some background:
In recent months I have gotten serious about replacing all the compact fluorescent lights and fluorescent fixtures on my property with LED equivalent bulbs.

Two things made this now economically feasible:
1. The price of LED replacment bulbs has come down dramatically in the last year. For instance, you can now buy 60watt equivalent warm white led bulbs at the local Dollar Tree for $1.00 each. The local state "energy trust" also subsidizes bulbs at local retailers (the best deals seem to be at the local Costco), reducing the higher wattage equivalent bulbs (75W and 100W equivalent LED bulbs) by about 75%, making them also affordable.
2. The price of 48" LED fluorescent tube replacements has also come down in cost -- a case of 20 from Amazon can be had for just a little over $5.50 per tube).

I had been keeping an eye on the various 12v DC flexible LED strip lights being produced in China, and was, at first, planning on replacing the 48" dual tube shop lights in my workshop with those, but the more I read about them, the more problematic they seemed. There were two primary problems:
1. The flexible LED strips had high power SMD LED chips on them, but, by themselves offered no heat dissipation, so people who simply stuck them onto various things found that they burned out quickly due to overheating, and the adhesive backing on the strips came unglued when the strips heated up.
2. Using these flexible strips due to the above issue required mounting them on aluminum bar stock to act as a heat sink, and use of special heat-tolerant adhesives to make them stay "stuck". This added extra cost and time.

Due to these issues I decided against using these flexible LED strip lights.

However, in the last year, I have seen another "led strip" light coming out of China on Ebay and Aliexpress. These also were 12V DC, but were rigid strips -- the SMD chips instead were mounted on an 1.5mm thick aluminum stock. Like their flexible "cousins", they too could be cut every few inches to whatever length was desired.

As time went on, I saw these rigid strips being produced with double-rows of SMD LED chips. This combination was capable of producing the lumens per meter that I wanted -- about the same or more light than fluorescent tubes produce. The most common length sold is 1/2 meter (50cm), probably because 1 meter strips would cost more to ship from China

As more time went on, I saw Chinese manufacturers offering these strips "bundled" with:

• extruded aluminum channels (to hold the strips and act as a further heat sink),
• plastic covers to protect the strips both in clear and "milky" translucent versions,
• end-caps,
• and mounting clips.

Back to the project:
So, i got to thinking, maybe instead of sending that old busted trouble light to freegeek to get it properly recycled, why not order a few 50cm "bundles" from China and convert the thing into an led trouble light.

So to do this I ordered:

1. 5 50cm bundles from china for $18.91 ($3.78 each including shipping),
2. a replacement spst switch from digikey (the most expensive part due to shipping),
3. and a 12v male cigarette lighter connector from China on ebay for about $1. This allows me to use the light connected to ubiquitous cigarette lighter sockets in cars and boats.
4. I also found and ordered from china a female 5x2.1mm 12v barrel connector to female cigarette socket adapter to use with some spare ac/dc 12v switching power supplies from old equipment, so i can also use the light on 120v ac house power.

Because most of the parts were coming from China, it took about 4 weeks for it all to arrive, but this was not something i had to rush to complete -- it was an opportunity to get my hands on these rigid 12v led strips and try them out.

There are many variations of these 50cm rigid LED strip "bundles" on ebay, but I wanted the following requirements to be met:

• the double-row version to get as many lumens as possible,
• warm white (2700k) because it is easier on my eyes,
• a "milky" translucent plastic cover to reduce glare,
• and an extruded aluminum channel "holder" that would fully capture the strip, would hold it close to the top surface so it would eliminate extraneous shading of the strip to get the widest possible angle of dispersion of light, and would also allow multiple mounting options, including drilling through the back of the extrusion and having enough space below the strip to accommodate a screw head.

I found only one bundle that met all these requirements, and, the extrusion also has lots of ribs, so it also has great thermal dissipation due to the increased surface area!

When i found this, I immediately thought about its possible application on boats for general interior lighting.

Here's a link to the ebay listing:
http://www.ebay.com/itm/152146363315

Anyway, back to the trouble light resurrection project. The 50cm strip was about 1.5 inches too long to fit inside the trouble light tube. However, these rigid 12v dc strips can be cut every 3rd set of chips, as can their flexible "cousins" to make whatever length desired. So a quick snip of the strip, extrusion and cover with some tin snips and I had the perfect length.

I then drilled 2 holes in the bottom of the extrusion about 2 inches in from each end big enough to allow a #6 machine screw to go through. I carefully marked the opaque back of the trouble light tube and drilled matching holes there. I left the unused mounting clips on the extrusion so it would leave an air gap between the back of the extrusion and the back of the trouble-light tube when the 5/8" machine screws were tightened up. (I wanted as much passive heat dissipation as possible via air conduction.)

I replaced the damaged switch with the new one I had ordered, wired the pigtails from the LED strip to the switch and the incoming existing 15' wire,
cut off the wire at the plug housing that held the damaged transformer, and connected that end of the cord to the 12v cigarette lighter male adapter. I then hooked up a spare 1000ma AC to DC power brick with a 5x2.1mm barrel connector to the female 5x2.1mm barrel connector to female cigarette lighter adapter from China, and I had a working LED trouble light that can be used both on 12v DC and on 120V AC!

The end result is what you see in the attached pictures. I plan to replace the double nuts with cap nuts or nylocks to look better, but its functional until I get to the hardware store.

It's been a fun project, and i really like having been able to resurrect that old trouble light. I think it might actually be a bit brighter than the original 15" tube was. I took a measurement of the current being drawn at 12v, and it is drawing about 800ma, or 9.6 watts. T8 15" fluorescent tubes use 14 watts, so there's about a 1/3rd reduction in power used, and the LEDs should last for years.

I did an overnight "burn-in" test, and the extruded channel got pretty warm, but not too hot to touch (barely). This means that the combination of the rigid aluminum LED strips and the aluminum channel extrusions together do a sufficient job of dissipating the heat the SMD LED chips are producing, so these LED strips aren't overheating and should last for a long time.

The remaining 4 50cm bundles will get mounted under the cabinets above my two work benches (one in the garage, and one inside the house).

I am thinking of getting a few more to mount on my sailboat. I might get an RGB version to use there so i can run them as white or red to protect night vision. I might just buy the strips, and cut them into individual segments to convert the existing 12v incandescent fixtures. The 1&5/8" 12v segments could be mounted adjacent to each other and cover most of the base of the lights. I'd just solder them up together using recycled used 24 gauge phone wire to connect them, and would install a double throw switch to select red or white. I i will have to include a diode so that the red-only selection won't light up the other colors (white is achieved by illuminating all 3 colors).

As i said earlier this has been a fun project to do, and doing the research required I learned a lot. I also confirmed that these double-row rigid LED strips are very useable. My total cost was about $10, not including the remaining 4 50cm "bundles".

Attached are pictures of both the 50CM rigid led strip "bundle", and the completed project (the project pics will be attached to a "reply" to this posting due to the 10 attachment limit per post).

Links to the other parts ordered from China will follow in a "reply" due to forum length rules.

I hope folks enjoyed reading about this trouble-light "resurrection" project.

Philip