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| Got Jacked with Fake Parts |
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| Ground_Loop:
I thought it would be instructive to roll my own PWM BLDC motor controller. Started with a random PIC from the bin with no PWM peripheral. I got the carrier solid at 10 KHZ, PW responding nice to input pot, and electronic commutation all working perfectly. Having done that I started on the power side with some IR2101 driver ICs and some FETs. All wired up and driver ICs are behaving strangely. I could not get a high-side pulse and the low side pulse was not only inverted, but responding to both the high and low inputs. All three were performing identically which made me assume I just did something wrong. After several hours of checking and rechecking I concluded that the gate drivers are the problem. I recalled getting them off either Amazon or EBay. I placed a quick order with Digi-Key for new drivers. Upon arrival and replacement, my motor fired right up. I don't know if they were outright fakes or factory rejects, but they looked completely legit. See image below; top real, bottom fake. I've had bad luck with Amazon and EBay in the past and should have learned something. Ironically, the Digi-Key price is usually in line with most others the only difference being that Digi-Key is a bit high on shipping. Live and learn I guess. |
| Siwastaja:
Its not "bad luck" with Ebay/Amazon, it's completely normal and as expected. Just say no, it's always a massive waste of time. Always buy from proper distributors, pricing is the same and the only difference is minimum value for free shipping but that isn't that bad if you can accumulate a few projects together or get something you always need in your lab like some missing resistor/capacitor values, connectors/pin headers, wire, solder, etc. |
| Miti:
Rub some acetone on them and see how legit the fakes are. |
| BrokenYugo:
Only time ebay/amazon/ali chips are worth messing with is if they're old NLA parts or maybe super jellybean stuff, and then expect getting half for free because they're not as described (pulls rather than NOS), remarked lower spec parts, outright inoperable fakes, etc. |
| VK3DRB:
This sort of crap does not only happen through eBay. A manufacturer on the Chinese side was assembling an engineering build of 100 8-layer SMT PCBAs with BGA's, UDFNs, QFNs, 0402s etc for me. No problems with the raw PCB, the component placement or soldering. The build quality was excellent. But they had a problem with the LCD backlight driver chip TPS61160A - a few volts output, rather than around 18V... on every board. These are only 40 cent chips from TI but the manufacturer had apparently procured fakes. There were two critical value resistors on those boards that had to be 0.5% tolerance and I specified Yageo (I have never had a problem with Yageo). It turned out they some were as much as 1.3% out - some high, some low in the same batch. This caused problems, taking a lot of my time debugging the issue. The manufacturer blamed Yageo. Then they said maybe their reflow oven temperature profile was set too high. To feed me such :bullshit: leads me to suspect they most likely they cheated by using generic resistors than Yageo's quality resistors or they bought fakes - probably the former. |
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