Also, since this whole setup is meant to provide some ambiental lighting (as opposed to, say, lights for the workbench), i won't be needing to drive the LEDs terribly hard. Between that, and wanting to keep things as simple as possible, i decided to go with the cheapest (and arguably the most dangerous) method of using a capacitive dropper, powered from the mains. The bulk of the idea came from Big Clive (of bigclivedotcom fame), and all the teardowns and reverse-engineerings of cheap LED lightbulbs as well as some of his own designs.
Now, it should go without saying that, since it's not my first rodeo, i have no qualms about going with a non-isolated mains-powered solution in this case, mainly because i plan on using a beefy mains power switch, as well as because the LED strips and whatever exposed metal contacts they have, will be well out of reach, so there should be almost zero risk of any unpleasant electrical events.
One step at a time though, and it's usually advisable to start with the first one. I chose one side of the "mechanical" part, namely assembling the LED... umm... fixtures, i guess? No rocket-surgery involved, though. Just the LED strips (which conveniently included some holes here and there), two strips of wood (roughly 2x5cm / 1x2", and however long they ended up being), and a liberal amount of thumbtacks. Pretty soft wood, possibly pine, so not a lot of force necessary. Although i did take the liberty of gently tapping some of the tacks with a hammer, just to make sure they had gone in all the way. Now, for the electrics...
As a preliminary test, i cobbled together ("deadbug" / point-to-point style) the necessary circuitry, along with some crocodile-clip leads (aka alligator leads), and used the switch on a power strip for control. To keep an eye on the current, i also hooked up a multimeter in series with the mains input, and two 220 ohm resistors, "just in case".
To get a rough idea where to start, i looked up some capacitive dropper calculators online, and ended up on this site over here, which contains a pretty detailed procedure for designing one of these things from scratch. Since i had everything else pretty much sorted out already, my main focus was on figuring out the series capacitor value, so all that interested me was towards the end of the page, namely the "1uF allows for up to 69mA".
First try, starting real slow, with a 100nF X2 series capacitor resulted in a bit over 6mA passing through the circuit, and a dim glow on the LEDs - so far, so good. Bumping that up to 330nF got the current to 20mA, and a more noticeable glow. I think 470nF might just be provide the "Goldilocks effect" i'm after.
Aaaand yup, 30mA on the nose - i'm happy with that. Then again, the 680nF one does let them go brighter, at 40mA. I don't seem to have the power supply from the TV these were in, but photos of it seem to indicate it was capable of driving the backlight at up to 190mA or so. That, coupled with the large copper areas on the strips themselves, to which the LEDs are soldered to, hint to me that they won't even approach "breaking a sweat" even at 40mA.
Right then, with that out of the way, on to the mechanicals, part two. Now, since i had already decided where i'd want the "control panel" to sit (between the windowsill and a sort of "secondary" windowsill, set at a bit of distance from the former), and had also decided on the somewhat chunky switch i was going to use, i needed a palm-sized piece of something reasonably thick and stiff to mount it into. Fortunately, i remembered i had bought a ~5mm (0.2") thick piece of transparent acrylic a few years ago (manufacture date on it said 2014) for a project that never came to be, perfectly suited for this task, so i lobbed off some of it.
Now, since i don't (yet?) have a router or a milling machine of any sort, i went at it the smart-caveman way - drilled a series of holes around the outline of the cutout the switch needed, ripped the center out and filed the sides flat, just enough for the switch to snugly squeeze through.
A bit of elbow-grease (and a certain amount of time spent sweating and cussing) later, and the aesthetic(?) part of the panel is complete. Now for the "behind the scenes" stuff. Which won't actually be all that "behind the scenes", what with the transparent nature of the panel, but still...
Not that i'm "paranoid" or anything, but i'm somewhat wary of making installations like this terribly permanent, hence why i decided against using anything like cyanoacrylate (aka crazy glue, superglue etc.) to hold things together, so i went with my big roll of trusty 3M 9087 double-sided tape - plenty strong enough for these single-digit-gram-weighing things. You'll note that, wherever possible, i taped up more than one side of the respective component, just to have more than one axis of adhesion (in case that's a thing).
Not looking all that shabby from the top, eh? I even counterbored / countersunk the hole for the head of the screw holding the bridge-rectifier - on one hand, to have the top of the panel nice and flush, and on the other hand, so the screw would reach through enough to reliably thread a nut on the other end. That, plus drilled a hole for the mains input to loop through, as a makeshift strain relief of sorts. Still better than it hanging just from the solder joints, anyway.
Back side didn't come out too pig-ugly either. Even though the whole setup's not isolated, i still went ahead and slapped on a couple layers of heatshrink tubing on the mains input lines to the rectifier. Never hurts to have isolation - even though the nature of this renders that point entirely moot, but still...
Aaaaah... The camera doesn't quite see things the naked eye does, though - the contrast is not quite that stark (the dark's not that dark), but it does throw a soothing wash of just-enough light, and nicely diffused as well.
Yes, the whole thing is janky as all hell, but it works, and that's all i care about. As the strips are sitting on top of those studs(?), they don't interfere with the curtains - not that i use them anyway. And i've tried angling the strips (ie. resting one edge against the wall), but that only reduces the light that gets thrown over the "front panel" of the curtain-rails. I guess that, between the thickness of the wood strips, the height of the above-mentioned panel and the throw-angle of the lenses on top of the LEDs, there's a happy coincidence.
I might decide to throw some double-sided tape on the underside of the control panel, just to ensure it against sliding about, but that doesn't seem to be an issue just yet.
And i'm not all that worried about the underside either - i'd have to be REALLY determined, not to mention reckless, to be able to stick my fingers under there and get zapped. So i'm not really concerned about that either.
All in all though, i'm pretty happy with how this turned out. And i could be wrong, but these might be an ever so slightly "warmer" white than the ones i tacked onto the back of my acoustic panels. But either way - nice cheap ambiental lighting, me likey.
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