atomic_fungus (atomic_fungus) wrote,

#6337: The fifth time was the charm

Went out at lunchtime to get my plate renewed. It was, of course, a huge pain in the ass; the currency exchange nearest work was on Roosevelt Road, which is in the process of being resurfaced, and naturally they pinched the road down from three lanes to one right at an on-ramp so it was actually four lanes feeding into one. The last mile to the currency exchange was literally half my travel time.

But--miracle of miracles!--they were able to renew my sticker. It only cost me $111.50, of which $10.50 was service fees. Argh etc.

Made the mistake of deciding I would celebrate with a McFlurry, so I stopped at a McDonald's on the way back to work. Sat in line for three minutes with no movement whatsoever, so I parked and went inside instead.

Got back to the office with five minutes to spare.

* * *

Yeesh, tell us how you really feel. But at least I'm not the only one who thinks McCain ran an incompetent campaign in 2008:
Humans, however, will remember too the half-hearted, half-assed, and half-witted bumble for the presidency, inflicting by force of his own lacking humanity and manifest unfitness for the office, the last disastrous regime upon America, such that it could not be dislodged until the 22nd Amendment came to the rescue, just in the nick of time.
And then there's his thumb in the eye of, well, the entire right wing:
That he is the sort of man who would drag himself to cast the deciding vote to thwart the will of the vast majority of Americans in ending the disastrous experiment in full socialism that was ObamaCare, contrary to his party, president, and simple mathematics, amidst the ravages of brain cancer, really tells you more about the man than anything that two thousand days of beating and torture at the hands of inhuman communist bastards ever could.
More and more I find myself ashamed to admit I voted for the guy in 2008.

Oh, well.

* * *

You might want to listen to people when they tell you there's too much ice for your polar joyride.

Also: ha, ha!

* * *

I kind of need this, too.

* * *

Today, on my way to work, I saw a car which looked like it had the Bentley insignia on it, but it sure didn't look like a Bentley. It looked more like a Korean car. It wasn't until after lunch I remembered it, and checked; turned out it was a Hyundai.


* * *

I dissected a dead LED bulb the other night. It died, so I took it apart. I did it wrong, but I should be able to dissect the next one correctly.

This is a 100-watt equivalent bulb (15w) and it has 49 surface-mount LEDs on a round circuit board. THe circuit board is backed with a piece of aluminum, which acts as a heat sink, and this is in firm contact with a steel conical section that forms part of the base of the bulb. Inside this section is the power supply; it's a switching power supply but I haven't been able to extract it from the potting material to figure out what voltage it supplies.

I could, of course, hook it up to power and connect a voltmeter to it....

Anyway when I pulled the globe off, it tore the LED circuit board loose, and broke the power supply board at the top where the terminals are. The globe is basically held on with silicone; there's a snap fit where it attaches to the base but it's not very robust. The silicone holds it firmly to the base, and it also retains the LED board in the base.

Digging the circuit board out of the potting, I find that there's a single 1/4-watt resistor linking the tip at the bulb base to the power supply board, but the process of pulling the thing out ruined it so I have no idea what its resistance is. The other electrode is the metal back of the LED board, pressed against the conical section, which connects to the ring part of the bulb base.

I see: on the circuit board, that resistor is marked "F1"--so it's a fuse, or at least meant to act like one. One side has a transformer, an inductor, and a couple electrolytic capacitors. The other side has the surface mount devices: some passives (resistors and caps), a bridge rectifier, a diode (I think) and an IC. The IC has very tiny print on it, ws9002s7p, and although I can't find a datasheet for that exact part, this looks pretty close to what I expect it is.

The board has some printing on it near the output side: "-225MA-15W". If we assume that means the rated output of the power supply (not a huge stretch since it's a 15W light bulb) then it means a voltage somewhere around 60-67 volts depending on how you figure the wattage. Assuming straight V times A gets 66.67 V when we do the math.

Unless I miss my guess, the power supply is meant to provide a constant current rather than a specific voltage. That makes sense, as the brightness of an LED depends on the current flowing through it, not the voltage present. And you'd hardly want to take even an array of LEDs and subject them to mains current; this seems much better, if a bit more expensive.

Amazing how far a little education in electronics and an Internet search engine can take you when it comes to reverse-engineering something. Heh.

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