It doesn’t take a scientist to analyze that this is too good to be true:
And of course that is exactly the way people get scammed: they see something that is irresistable and they buy into it.
At least this memory seems to work OK. One Memtest86+ without problems.
New Hynix 4GB 2X2GB PC2-6400 DDR2-800MHz 240pin DIMM Dekstop Memory For Intel from wwon_one
It is not the cheapest available as those are below 10 € and this was 16.80 € for 2x2GB.
Plus it’s Hynix. Hynix makes server memory so Hynix is good. Generic brands are not known for their server memory, because they do not make server memory. But if you make server memory, and enter consumer markets, you will use that skill and knowledge to make good memory still.
Looking at this price:
and wondering if Alibaba can only deliver counterfeit or bad parts, as their prices are 10x lower than this. I know Digikey packages and handles and so forth these parts with care so that will increase the cost. Conditions in China (referring to Alibaba) may but bit different, and employees may not have the slightest clue how to store or handle components. Who knows.
But I took time to send few diamond-rated sellers simple question: Where do you source these components from? Are they genuine?
If they have interest in customers then they should do everything to convince me that their parts are good and genuine. Or they may just answer yes they are and we get them from supplier, which of course can be a lie, conscious or not. But unless they have taken care of making sure they can deliver good genuine parts, they have no way of knowing.
The good thing about cheap parts is that they can work. Bad thing about cheap parts is they might not work. And that’s a problem when you’re doing something. It may not be such a large problem if you had a scope, but for me that’s the impossibly big problem. There’s no way of knowing for me if that particular part works as it was specified to work and in a circuit in a way the circuit was designed.
But still, Digikey is one damn expensive place for a hobbyist. eBay for instance has money back return policy and suppliers usually refund to avoid any conflicts. So that’s the good part (ironically). You can get your money back if what you received isn’t what it was supposed to be. And it seems Aliexpress has something similar:
Looking at this price difference between 1 and 500, the cost of handling is clearly visible:
So because the labor is expensive in west, it must be billed from the custom at these increased prices. So it is definitely possible to source components cheaper from China and have those components still be genuine. How big the price differnece may be? That is difficult to say.
So if this holds true I need to seek for another source of LED lights. I might measure the Lux and if possible from those numbers calculate if they produce anything close to reasonable.
Had to do little test. Took a sun filter out of my telescope and looked directly into the 100W light (always wise thing to do) and while there were little difference in brightness between the individual dies, they all seemed to light up.
So based on that simple test I will not worry myself too much with this detail. Maybe they aren’t the best but so far my “defective” LED lights are meeting my standards very well.
But it is very hard to tell if they all light up; up until one point it seems half of them are lit up and half are not. So half may in fact be dead and the intensity of the light interferes with this simple test. More investigation is definitely needed.
Looking at Sure Electronics’ picture of their 100W LED it seems they might be honest seller.
They were mentioned on the video comments above. So the next lights I will order from them.
Paul Mathews writes:
A few points: 1. encapsulant over LED dice is soft, and it is fairly easy to damage the wirebonds on these multi-chip LEDs with any amount of pressure on the encap. The result is usually a short or intermittent short, which would explain the patterns you see. The lack of mechanically protective packaging is of more concern than ESD protective packaging, in my view. 2. Some people think that perfect matching is essential for proper current sharing, however, most high output LEDs are fairly resistive (see slope of VI curve) so ‘self-ballasting’. This accounts for why strings of different effective lengths will still light up. 3. As others have suggested, these are probably reject units, but possibly just badly handled units. In my experience, many Chinese suppliers are capable of producing very high quality goods, but there are also plenty of vendors who will sell low quality stuff to anyone willing to pay. I am an LED illumination design engineer.
And more about the issue:
And at about 6:40 the phenomenon is clearly demonstrated. Extremely interesting stuff. And essentially these cheap Chinese lights are burning all the electricity up as heat. Paying 25 € for quality 100W LED seems to sound quite reasonable idea.
I am beginning to wonder if many of the components I am buying off of eBay are in fact counterfeit.
Sometimes the plastic casing on TO-92 looks very cheap and rough cut and now my 20A diodes’ leads look so flimsy I am having hard time believing they could carry 20A of current. At least those leads will get very very hot.
Received two of these this week and should I had known they were no good.
First problem was they came without shunt resistor so they cannot work to begin with.
Second problem is they were advertised 0-100A and if I put 100A through those wires they will vaporize.
And third problem is that I believed $2.50 device could really handle that much current.
Now I am looking for either proper current panel meter or accurate enough clamp meters.
One positive thing is the seller unitednewfrog gave me full refund and if I now find what value resistor that is I may just solder one in and hopefully use them as low-current ammeters.
I don’t know do they do this on purpose or do they simply forget to add shunt resistor which is the essential part in ammeter.
Don’t buy these ones unless you only need to measure small voltages and resistance.
I was measuring efficiency of my setup and for some reason I could not push current through the meter.
I opened the meter to see if I could hook wire directly to something since the connection felt loose.
The moment I got it open, the whole connector fell off. I had ripped off of the PCB. No wonder current is pushing through I thought.
These are excellent cheapies for anyone measuring voltages and resistance once or twice a year but not good for anything other.
You have been warned. I did not listen the warnings and bought two of these over some number of years. But they served me well until I began to do testing actively.
But it’s expensive to get expensive, or, at least better quality meters. 40-50 € a piece minimum. One for current, one for voltage, and then double that for input and output, and you got 160 euros.
Cheap 87 € including P&P from UK.
I am also trying to get secondary 10Mbit connection so that I can do some more routing.
I also have one public wlan idea in my mind which I would like to try. I could dedicate the 10Mbit for that.
And the traffic would be routed through VPN or Tor so that it would stay that way.
100% ghetto but it works (well enough). Can use the existing 5 A 12V supplies to supply this enough current for most of what I do.
And the existing ones as well are super cheap chinese AC-DC power supplies but this will add the constant current and constant voltage.
And bunch of these
Also this one has quite nice analog look in it with 2 A capacity so perhaps for something smaller than what I am thinking of doing.
I don’t know but the following one looks better than the first one but is only 8 amps. But provides like real specifications which is good.
But it lacks fuse and is more expensive than the first one which has one.
Another slow day at work and eBay surfing and found these and could not believe my eyes.
First I thought it was memory but it’s SSD and 10TB of it. And connected using PCIe.