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Desk Light Transformer

I have a fluorescent desk light which houses a small transformer with the prongs and plugs into the wall. The original plastic shell/cover broke and rendered the light unusable. I believe it broke due to the brittleness caused by the heat from years of use. Anyway, I like this light and decided to make another cover out of wood which came out pretty good. My only concern is that heat again. I drilled little holes to help vent it but it's still a concern. I used a small piece of black walnut I had laying around to make the shell. I used my thermal imaging device (Flir adapter for phone) to read the temp of the unit which reached over 100 degrees. Therefore, I'm wondering if this would be too hot for the wood and can it cause a fire?

Reply to
Meanie
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Wood starts to char at about 220F. Dry wood won't ignite until closer to 400F.

But, I'm not sure how much cooler (than charring) you can safely operate. I think even at ~200F for long enough time you'll see some discoloration of the wood. Whether/when that poses a fire risk would be hard to say...

Note that you also have to consider what happens if the transformer fails or degrades, over time.

Reply to
Don Y

you could add a thermal fuse to open the circuit if the temperature exceeds the combustion temp of the wood. this also protects from malfunction overheating.

why not convert to a LED bulb/s nearly zero heat that way:)

Reply to
bob haller

I'd be more interested in replacing the xformer with something like a "brick" salvaged from an LCD monitor or laptop. You know it's ratings (power) and know that it's been designed in a package that can handle those limits...

But, that means knowing the output characteristics of the old xformer

Reply to
Don Y

Good info. Thank you

The failing suggestions leads me to think that's what may be happening. Because it become hot when I plugged it in, I unplugged it when I'm not here. Before posting this question, I plugged it in again and felt it after a few minutes. It's cool to the touch. Not even warm. Therefore, I left it overnight and as I type, it's still cool. What the hell?

Reply to
Meanie

Agreed. I've upgraded my entire house to LED but I have a problem with throwing something away if it can still be used or still serves a good function. My mindset is if I can repair, why buy anew. I like the articulating features of the lamp due to it's reach. If I can replace the bulb to LED, I'll go that route.

Reply to
Meanie

Even without a "load", a transformer "consumes power" in the form of eddy currents in the laminations (of the core).

You may, also, have a failing transformer (winding that is shorting out due to a failure of its insulation).

Or, a failure in the "load" that is causing a persistent (or intermittent) additional burden on the transformer.

[Note that the transformer is undoubtedly sized JUST BIG ENOUGH to handle the expected load. If that load is changing, then it is possible that the transformer is being overtaxed and getting warmer]

If possible, I'd look at the transformer to see it's rated secondary voltage (is it a transformer for an incandescent lamp? or, a *ballast* for a fluorescent one??!) as well as its power rating (may be present on a nameplate, somewhere).

If possible, consider replacing it -- even at the inconvenience of having to rewire the lamp -- with an external transformer. I've done this with one of the 12V halogen fixtures, here. And, I'm currently looking for a suitable "power supply" that I can modify (variable output/"dimmer") for an "illuminator" (columnar light source) that I use with my stereomicroscope. Easier than trying to find the original (old!) device.

Reply to
Don Y

...you sure write a lot without reading his 1st sentence!

"I have a fluorescent desk light..."

Reply to
bob_villain

And there could be a transformer to lower the mains voltage, then a seperate ballast.

Reply to
James Wilkinson

100F, not so bad. 100C, bad.
Reply to
James Wilkinson

There are LED tubes available on Ebay to replace most fluorescent tubes. Then you just remove all the ballast stuff and feed mains directly to the LED.

Reply to
James Wilkinson

Then I'm safer. F it is.

Reply to
Meanie

Yes. Some folks jump to conclusions -- without having (or trying to ascertain) the facts, first!

There are fluorescent lamps in every LCD monitor. And, a ballast *in* the monitor. Yet, all ALSO have a power supply -- either internally ALONGSIDE the ballast/inverter *or* in an external brick. The fact that the transformer was *in* the "PLUG" makes it even more likely that there was a separate ballast elsewhere in the light. Otherwise, you'd be pushing several hundred volts up the POWER CORD into the light (with

*more* than two conductors).

The OP could have clarified this EXPLICIT question. Villabozo apparently thinks he can read minds and see through walls and across large distances. Legend in his own mind.

Reply to
Don Y

Ah, but I *can* figure out the obvious!

Reply to
bob_villain

100F is near enough body temperature, I can't see wood getting upset by that, otherwise you touching a piece of wood would damage it! But are you measuring the hottest point?
Reply to
James Wilkinson

Isn't he some TV DIY show bloke? Or just naming himself after one?

Reply to
James Wilkinson

No idea what goes on in his little mind. I don't see his posts (filters, here) so wouldn't have known about it without seeing your reply.

Sad when people don't think about whether or not their conclusions "make sense" -- even given limited information available in a post.

"Let's see... if THIS is true, then all these OTHER things would implicitly follow. (high voltage in power cord, more than two conductors -- possible... but probable??) Do they ALL make sense? Are they all LIKELY? Esp given the price and safety pressures applicable to the item??"

Reply to
Don Y

I suspect there is a problem in the inverter *in* the lamp ("electronic ballast") that may be intermittent. So, the wall wart sees a higher load and gets warm.

Hard to tell from the 2-terminal device in the photo (black, one lead in a "curl") but that may be a temperature operated cutout. Or, a PTC device (resettable fuse)

Reply to
Don Y
[snip]

I had a light like that, and didn't need the transformer any more. I put it back in because the lamp needed the weight to keep from falling over.

Reply to
Mark Lloyd

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