If you’re looking for a super cheap way to add LED lighting accents to your house, then this hack is for you! Corn-cob style LED light bulbs can be had for a few dollars. The bulbs include driver circuitry, and 8 LED arrays! All you have to do is take it apart.
[Martin Raynsford] stumbled upon this idea when trying to think of a way to light his laser engraving enclosure. It originally came with a regular light bulb, but it didn’t distribute light nicely and was in the way for some of his other planned upgrades.
Not wanting to add another DC power supply to the mix he remembered an old corn-cob LED light bulb he had — as it turns out, they’re pretty easy to take apart! Solder some longer leads on (take note of how they are wired, some are in series, some in parallel) and you’ve just made yourself some easy to use LED accent lighting!
Of course you could just buy those cheap LED rolls from China nowadays for next to nothing for your accent lighting.
[via Hacked Gadgets]
I have bought several of these cheap chinese LED lamps, and the drivers are frankly lethal, they either have severe lack of isolation or they are simply not isolated at all. From what i can see of this driver it looks like it isn’t isolated which means every metal point on those LED strips has a lethal electrical potential to ground.
By all means buy cheap LED lamps like this to use the LEDs or heat sinks, but please for the safety of your self and others, throw out the driver module. Apart from being badly isolated it is also quite likely to catch fire at any point because of severely underrated components.
I agree. I took apart one of these lamps that was partially melted. The driver was a joke.
Who the hell would be crazy to use the “driver” on those things… Please Hackaday try to better research on what you’re actually encouraging…
Might as well just push your fingers into a plug or throw a match at your curtains, at least you’d have more predictable outcome that way.
Or just watch this: http://www.youtube.com/watch?v=n3ci4nlKhEk
Yep. Touching any exposed parts will be a nasty surprise! https://www.youtube.com/watch?v=n3ci4nlKhEk
Some of these ‘corn’ LED bulbs have lower life expectancies than CFL ones. Furthermore, they use dirt cheap LEDs that often have a much lower CRI, and one must also not forget the safety considerations that were ignored by these bulbs. Aside from using them for projects like this one (where I would have used high power LED strips instead), you’re best off buying higher quality bulbs with proper drivers and beefy heatsinks. Their cost is very comparable to these kinds, and you’ll get an overall better experience.
Agreed, I had some cheap LEDs that lasted about 1.5 years before dimming to nearly unusable levels. Nowhere near 50,000 hours. In some cases they’re overdriving the LEDs to get a few extra lumens out for lower cost.
Well, there are differences even between those cheap eBay LED lights. Some of them have a “proper” SMPS driver circuit and cost about the same as those dangerous ones in the youtube video. It depend on your lucky pick when buying them online, but you can judge the type of the driver when seeing the bulb in real: those dangerous ones, with galvanic connection to the mains, always flickers a bit. Look at the lamp lit and move your eyeballs left to right and back again several times quickly to disable your POV and if it flickers, you will percieve the flickering as several parallel images of the bright LEDs .
The capacitive ballast is actually remarkably efficient and reliable if (big if!) it is designed properly. That means using proper X rated caps and putting in enough surge protection. I’m sure the really cheap ones won’t be, but that doesn’t automatically make it (the idea, not the implementation) a bad design. Poorly designed switchers exist as well.
The lack of isolation is of no issue if all the wiring is protected from accidental contact.
The lack of http://en.wikipedia.org/wiki/Nuclear_safety_systems is of no issue if all the rest of the http://en.wikipedia.org/wiki/Nuclear_power_plant works as expected!
why this is a bad idea? because the color rendering index and light refraction will suck so much that anyone will give up on that light after a few minutes.
There’s an easily accessible 24V supply for the steppers in these lasers. That should be ideal for safely driving these strips in parallel. They’d probably need a current limiting resistor (unless they already have one) but that’s it. Safely hacked, rather than unsafely disassembled but essentially left unchanged.
What happens if your vcc is lower than your Vf? I have a 3.7 V LED but im only driving it with 3.3V is it necessary to use a current limiting resistor?
Short answer, No.
Long answer: If the forward voltage of the LED is low enough for it to light in the first place, the voltage across the LED is not high enough for it to ‘saturate’, if you will; meaning it doesn’t allow the maximum amount of current to flow through it, therefore self regulating the current. Adding the resistor in the first place is because we want to get rid of the unwanted voltage. This means that if you have a perfect, ideal 3.7V 20mA LED, and you put it in a 100% stable, precisely accurate 3.7V power supply, the current will be exactly 20mA and you don’t need any resistors either.
Why we don’t use voltage supplies to drive LEDs is because what we actually want is the current to be precisely 20mA, it doesn’t matter what the voltage actually is. And getting a stable current is much, much easier than getting a stable voltage due to temperature changes and voltage sagging under load, not to mention each LED will have a slightly different ‘ideal voltage’.
another reason is that LED voltage lowers with heat, a LED that runs at 20ma and 3V when cold might easily draw 50mA at 3V when given time to heat up resulting in an runaway scenario where the LED burns itself out.
Wooden holders with mains-potential LED boards, uninsulated wire connections. I just hope that fire department and ambulance is close to this guy’s home.
I’ve got a bunch of these in my home and I love their price and efficiency. Yes, you do need to take care regarding high voltage exposure, but I remember there being the same concern regarding the good old fashioned light bulbs when broken (easily). The CFLs have mercury in them and I don’t want to breath that. Also, the corn-bulb build style is more accommodating to the nature of surface mount LEDs and so heat is less of an issue. No heat sink is necessary and they are the most reliable kind of LEDs available. Also, if there is a problem, the bulbs are a cinch to fix. Most out on the market are of cheap Chinese manufacture, with most being OK, but the occasional one has a bad solder or such which is no problem for a technology geek. Just don’t stick your fingers where they shouldn’t be and don’t lick these bulbs and you will be fine. :-)
I have done something similar. For anyone taking this path:
1) the individual parts can be spread out, and then wired in a loop. If you make this loop a few meters in diameter, it can pick up quite a bit of magnetic flux, like nearby lightning, which the driver is unlikely to handle well. Make sure to run the return wire along the same path, instead of creating a loop.
2) I think I broke my LED’s (and then some more while testing), by connecting the LED’s to an already powered up driver. for example when inserting an Amp-meter in series with the LED’s. It looks like the driver builds up a charge, and the peak current when the LED’s are connected to the driver is too large for them. So always make sure the LED’s are connected to the driver before connecting mains to the driver, and disconnect mains before inserting A-meters in the LED string.
(The usual watching your fingers applies, especially in 240V countries, or when working near grounded objects, or wet floors)
I also found out that replacing the driver is easy (if you can find a new donor), but replacing all the LED’s in the string is a lot of work.
Next time I will defiantly look for very low-power 12VDC led’s, with an easy to replace socket, and wire them all in parallel, connected to a high-efficient 12V mains adapter.
The reason your LEDs broke when you connected them to a powered driver is that the drivers for LEDs are usually constant current. This means that with no load the voltage will climb to the maximum possible. Since there is an output capacitor on most drivers these will cause a high current pulse when the LEDs are connected.
You are lucky the voltage didn’t build up high enough to set fire to your output capacitor.
I got a couple of these off amazon.. they both lasted less than 1 month, they are easily disassembled, but I haven’t troubleshooted the boards to find point of failure. I have a smaller one off ebay that illuminates my freezer. it still works of course. that is the perfect use for led lighting. less heat made, and leds are ideal for cold tenps, compared to cfl and incsnfescent