Hi all! Thanks for your interest... this is my first post here but hopefully one of many as I dive into this world. For now though, I'm still very much a beginner and could use a little help:

First I'll explain my project: I have designed a 5"x5" wood lightbox. The top and sides are built with thin wood veneer that light shines through. I've found that I need an LED of at least 500 lumens, preferably more, to get the box to glow in daylight. So far the electrical components are VERY DIY. I'm using this 12v G4 LED (https://www.1000bulbs.com/product/115388/PLT-300247.html), and a 12v DC converter I found (it's 300mA... probably too much but I can't find a datasheet for the bulb).

I'm a little worried about selling these things because of the potential fire hazard... even after I find the right components. The airtight environment inside the wood box could make it get really hot in there. Does anyone know of any pre-certified (probably by UL) led modules that I could simply attach to the light, and not worry about wiring or heat? This just might allow my to say I'm simply making a lampshade for a legal lamp. I've seen some interesting remote-operated ones, but they either appear to be too bulky or dim. Any suggestions? Experience with selling your creations?

I've attached some photos of the project.
Thanks!

 

12V @6W is 500mA, i would use a 2amp psu ready made cctv type. As for the heat generated put ventilation holes in the top and bottom for circulation of air.

Found this UL website, maybe you've seen it before..

http://www.ul.com/marks/ul-listing-...ing-guidelines/specific-guidelines-and-rules/

 

You could mitigate risk to potential customers by fitting a simple thermal fuse inside the box (has to be crimped, spot welded or via screw terminals, no solder for obvious reasons).
This is what i've done on various projects, in fact I don't do any projects now without a thermal fuse. They're so cheap that I can't understand why they're not more common.

A recent project was a remote temperature controller for a 2000W heater, the control box has a thermal fuse before the PSU and there is remote thermal fuse attached to the heater itself, which cuts the feed to the main relay if a fault occurs.

You do need ventilation as well, remember heat rises, so heat leaving a hole at the top will be replaced by cool air coming in at the bottom. Just don't forget that airflow means dust, which is another good reason for thermal fuses.

 

Thank you, I think ventilation is definitely key.. just need to figure out how to put holes in the box without letting light escape. Or perhaps use metal heat sink that penetrates the box. As far as a thermal fuse, do you need it to match the current? For example, if I use a 12vDC 2amp psu like Dodgydave suggested, would I need a 12v 2amp-specific thermal fuse?

 

12V @6W is 500mA, i would use a 2amp psu ready made cctv type. As for the heat generated put ventilation holes in the top and bottom for circulation of air.

Found this UL website, maybe you've seen it before..

http://www.ul.com/marks/ul-listing-...ing-guidelines/specific-guidelines-and-rules/

Thank you! Is there a calculation for determining amps if you know the voltage and wattage? From what I know it's more of a crude test-and-see process.
I've done some research on the UL website and it looks like it'd be too expensive for the hobbyist to get a certification. But it IS legal to sell a product if you're using all UL listed components. I was considering something like this if I could find a cheaper version: https://www.earthled.com/collection...att-equal-dimmable-4-pack?variant=22542652356

 

Just an idea; for ventilation, make the opening non-linear. i.e. zig-zag, and coated in flat black finish so as to not pass any light. This is probably overkill, but you could also hide a small nearly-silent fan on the inside-bottom to draw cool air in at the bottom and force it out the top:

http://www.kr4.us/blower-squirrel-cage-12v.html

 

Just an idea; for ventilation, make the opening non-linear. i.e. zig-zag, and coated in flat black finish so as to not pass any light. This is probably overkill, but you could also hide a small nearly-silent fan on the inside-bottom to draw cool air in at the bottom and force it out the top:

Interesting idea! That would definitely add to the complexity of construction... might be a fun challenge. I'll give that some thought.
I thought about a fan but am worried about noise. I'm considering just attaching a heat sink to the bottom of the G4 base... perhaps with something like this (http://www.kr4.us/thermoelectric-cooler-40x40mm.html) in between if necessary. Not sure how I'd attach them.

 

I've done some research on the UL website and it looks like it'd be too expensive for the hobbyist to get a certification. But it IS legal to sell a product if you're using all UL listed components.

Even though UL would like everyone to believe that they are a government agency, they are not. In fact there are many safety compliance testing agencies -- both here in the US and other countries.

It is legal to sell a product without meeting UL compliance requirements. If your product does harm to a customer I would think that having the UL "sticker" would be of some value in court. Your idea of only using UL rated parts in the safety critical parts of the product is good.

Be aware that there are lots of things UL tests for. One example is that there are no openings that let a spilled liquid can get into areas with dangerous voltages. They also test that a product does not get too hot to touch if a component failure happens. To make things more complicated, there are many classes of products, each with their own safety requirements. It can be hard to determine which standard you need to comply with.

In summary. The general public perception is that a product is bad if it is not UL rated. The questions are... What does _your_ customer expect? Does your customer's expectation require UL or other safety testing? Is the customer willing to pay for the testing?

 

Build one. Put a thermometer inside, another one outside but nearby. Wait several hours. Compare temperatures.

See hot relatively hot the inside of the box gets. My guess is this will not be hot enough to cause any concern.

 

Thank you, I think ventilation is definitely key.. just need to figure out how to put holes in the box without letting light escape. Or perhaps use metal heat sink that penetrates the box. As far as a thermal fuse, do you need it to match the current? For example, if I use a 12vDC 2amp psu like Dodgydave suggested, would I need a 12v 2amp-specific thermal fuse?

No, you can use a standard 20mm fuse to protect the PSU, maybe punch a hole in the back and put a screw top fuse holder in. You'd want to put a thermal fuse on the mains side, before the PSU, cover it in sleeving to make sure nothing can come into contact with the mains. The standard value I use is 80 degrees C (176F), this is high enough to cope with heat from a PSU, but low enough to stop everything way before a fire could occur.

They're not voltage specific at all, they'll work at any voltage, but they are rated to handle mains voltage.

I know it's a really lazy solution, I know plenty of designers who would spend weeks and weeks designing a PCB/circuit to do the same thing, perhaps even fitting a cooling fan/controller, but seriously why reinvent the wheel when a cheap component will do all you need?