40
Condor
3y

I've just disassembled this LED floodlight that I bought a while ago. It's some stupid little cheapie from a dollar store, so I figured that there'd be shit inside. But I wanted that LED cob.. a power LED :3

Well, shit wasn't too far off from the truth. The component choice is reasonable, but the design of the bloody thing.. batshit insane. The LED floodlight is powered by 4 AAA batteries, connected in series. So 6VDC. That then goes into this little tactile pushbutton, into the LED cob and then a 4.7 ohm resistor.

Well that's a pretty easy circuit.. let's remove the batteries and the casement, and put it on the lab bench power supply. Probes connected to the circuit with only the resistor and the LED cob in between (I didn't want to deal with the switch). Power supply set to 6V, current limiting to 500mA, contact!! And it works, amazing! So I let it run for a while to see that nothing gets too hot.. hah. After a minute or so, smoke would come out.. LED cob was a bit warm to the touch but nothing too bad. But the resistor.. I could cook water on it if I wanted to! 100 fucking °C, and rising. What the F yo?!

So I figured that I didn't want to put the resistor in between there. Just the LED cob now, which apparently has a forward voltage somewhere between 3.2V and 3.3V depending on how I set the current (500mA and 600mA respectively). Needed a bigger heatsink though, so I jammed one of my aluminium heatsinks on there. And it worked great! Very bright too, as it takes between 1.6 and 2W of power. Just for a comparison, the lighting in my living room is 4x5W and the ones on top of my dining table are 2x3W (along with some TL bar that my landlord put there.. fluorescent I think). So yeah, 2W is quite a lot for an LED, especially when it's all concentrated into one tiny spot.

That said, back to the original design with the resistor. 2 questions I have for that moron that designed this crap. First, why use a resistor for a power LED?! They needlessly waste power, and aren't good choices for anything that consumes more than 100mA. You should use PWM for these purposes, or tune your voltage on the supply side. Second, why go with 6V when your forward voltage is 3.3 at most? Wouldn't it make more sense to use 3 batteries with 4.5V? Ah, but I know the answer to the second one. AAA cells aren't rated for high loads like this. So that's likely why the alkaline cells that I had in there before have started leaking. Thanks, certified piece of shit!

Honestly, consumer electronics are such a joke... At least there's some components that I can salvage from this crap. Mainly the LED cob, but also the resistor and the tactile pushbutton perhaps.

One last remark that I'd like to make. This floodlight was cheap garbage. But considering that you can't do it well at that price, you just shouldn't do it. You know why? Because consumers always go for the cheapest. Makes a lot of money to build at rock bottom prices and make shit, but it damages the whole industry, since now the good designs will go out of business. That's why consumer electronics is so full of crap nowadays. Some unethical profiteering gluttons saw money, and they replaced the whole assortment with nothing but garbage. I'm sure that there's a special place in hell for that kind of people.

Comments
  • 9
    I didn’t know @linux was into electronics 😎
    the things you learn on devRant.

    Also you are completely right cheap shit is usually just that!
  • 6
    First time I see @Floydian appearing under the @C0D4 nick too :P
  • 3
    @C0D4 Also it looks like @devTea ran away with mine, haha!
  • 7
    @Condor I’m the real condor now
  • 2
    @Condor not the first time though.
    Glad to see this taking off again.
  • 3
    @devTea hahaha, made my day! XD
  • 2
    @devTea that’s creepy and yet perfect at the same time 😂
  • 6
    I am confuse
  • 3
    @Linux I'm the real Linux now :3
    Anyway, it turns out that that whole avatar swapping fad became a thing again.. so I figured that I'd go with someone that I admire :)
  • 2
    @AlexDeLarge Ah, sorry about that :')
    (by the way I didn't know that you follow my rants! The more you know!)
  • 5
    @Floydian 😂 my evil plan is working
  • 2
    @Floydian @C0D4 just normal day at devrant
  • 3
    Best self-thread-hijack 😂
  • 2
    @mngr now that you mention it.. oh well :')
  • 2
    EE here: To answer the first question, the moron who "designed" this wanted or was told to increase profit margins for the product. It's not a high reliability design, so if you can save a few cents on a component or two (or even better, eliminate components), you do it because you are making a couple million of these toys. A couple million * a few cents is still a lot of $$$.
  • 2
    @codex653 Still though, you have to be at a certain level of evil to use a power supply (AAA batteries here) that aren't rated for this purpose (so 4 cells because during a loading like this the voltage drops significantly I guess), and a resistor that will be hotter than a steam engine when it's running. I get that saving a few cents can be an incentive for money-driven fucks like that, but can they really sleep at night like that? Knowing that it has significant flaws, yet have it sold regardless?
  • 1
    @Condor I guess we know at least one can since this atrocious thing exists! 😂 There are a lot of messed up businessmen out there who will sacrifice quality/safety for money IMO. Especially with cheaper end products like this.
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