EEVblog #533 - LED Fluoro Tube Teardown

What's inside a modern 18W LED Fluoro T8 replacement tube from German company Mueller Licht?

Datasheets:
(too short to be this LED)

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[precosky]

Quite the coincidence, just today at work I received an LED line array similar like this, but with lenses fitted for a machine vision application. The PCB and body/heatsink construction looks just like yours. Mine was made in the USA though. I called the company and talked to an engineer to talk about the design on the phone and he told me this design was both cheap to make, and a really good heat dissipator. Neat to see one cut open (without having to sacrifice my expensive machine-vision one!)

[ninetwothree]

Just picked one up at Aldi. I saw them last week and thought it would make a fun tear-down. Glad you beet me to it! You really saved me 24 bucks.

[FranLab]

Very interesting - and I do wonder how much operational life is actually shortened by the lack of thermal transfer behind the PCB, and also surprising that the heat sink is fully encapsulated in the plastic tube rather than being able to vent heat to the outside air. Fully assembled it would seem that temperatures would rise significantly.

[maqsoodu]

In theory, the thermal impedance from the pads to the tiny copper island is going to be around 60C/W. This will give a 6C rise above ambient. So your looking around 38C.

However, the Vf has a negative thermal coefficients, so in reality the power dissipation should be less and once the equilibrium is reached within the environment, the delta temperate should be less than 6C

[whitcwa]

The weakest part of most LED light bulb replacement designs are the aluminum electrolytic caps. I have already had to replace some caps in LED light bulbs. The CFL bulbs usually wear out before the caps dry up, but I have repaired several of them as well.

[nuclearcat]

What is quite interesting to check - it is power factor of such devices (how current follows voltage). As i know most of devices with diodes and cap sucks in this matters, and it will make a bit more on your electricity counter than your measuring equipment will show.

Thumbs up from Switzerland for the PB Swiss tools screwdriver!

[chadgdry]

I am always appreciative of your posts. Thank you!

[whitcwa]

It is important to move the heat away from the LED die. When the heat is spread to a larger area the temperature is decreased. The tube does dissipate heat to the outside.

[ponakka]

How do you feel after all devices are using switching power supplies and they cause generally more rf in higher bands than old fashioned lighting. Many radio amateurs have bad times in cities because of constant rf ringing in the bands. I heard some plans for future homes to incorporate low voltage rails for small load devices to connect to standardised dc psu. Poe is somewhat similar system at the moment.

You're always fun to follow. Thanks

[EEVblog]

Because it brings down the die temperature, which is the most important thing.

[nodrogawson]

Great stuff I think you may have converted me to LED lamps, you have shown me exactly what I wanted to know. Thanks for sharing.

[superdau]

Almost all of those switch mode current supplies use a sense resistor (look at the datasheet). Essentially they look for a certain (fixed, e.g. 0, 2V) voltage on the resistor. Exchange the resistor and you change the current. Ohms law is your friend.
I wouldn't try to get more light of a tube constructed like that though. With being totally enclosure in plastic you'll reach a thermal limit quite soon I think.

[jonathanmlang]

So what if this was put in a fixture with a magnetic ballast still inside? How would it handle the high voltage spike at power on and power off?

[Ghlargh]

While the light output of the LEDs may be a bit over spec (with new LEDs) you will have to take into account aging and the loss of light through the plastic tube.

Nice walkthrough and research in all.

[MysticalDork]

I am also in this boat, almost all the easily-available CCFLs around here are 2700k horrible yellow and look almost like low-pressure sodium lamps. Anything better is either impossible to find or prohibitively expensive unless one makes a trip to one of the nearby cities.

[lp]

I think the clearance is alright since everything is coated under soldermask which is protected from scratches by the tube.
I think that at the end, it is perfect to just stick the bare pcb without the aluminium frame directly under a shelf, to get a bright working light.

[EEVblog]

Because my main LED lights happen to be 4000K, so I either have the replace the lot, or match them. The camera does the colour white balance.

[gglovato]

low temps make everything yellow and dim, like you say, higher temps makes white "white" and looks more crisp and brighter.
i refer to any space: dining room, my room, my office, workshop, we use all 5000K or higher CFL/FL

[MisterMosfet]

Dave I am in love with that calculator ahhhh