Electronics > Projects, Designs, and Technical Stuff
Fake DS18B20
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james_s:
That would certainly be preferable. I'd be happy to buy a DS18B20 with a different brand on it if I evaluated a few samples and found them to perform equally to the Dallas parts. That's true of so many of the fake Chinese parts, the ones that work properly could be sold as compatible parts under their own brand and nobody would feel ripped off.
wizard69:
This is not a good idea at all.  I have nothing against competitive parts and marketed as such but really have massive hate against what are rip off parts -true fakes. 


--- Quote from: james_s on April 19, 2020, 05:00:42 pm ---Well if they fix the bugs so the fake parts are indistinguishable from the real ones I'd actually be ok with that. Then I could use cheap clones confident that my projects will work correctly instead of having to spring for overpriced genuine ones.

--- End quote ---

If you don’t like to pay for the genuine part design in something different.  Really it is that simple, use an honestly sold competitors product not something marketed to be a rip off. 
james_s:
I'm just talking about hobby projects. If you're designing something into a commercial product then it goes without saying that you should be buying genuine parts from a reputable distributor.

If it's coming direct from China and costs 1/10th the quantity price from the manufacture then just assume it's fake.

I've used quite a few ridiculously cheap Maxim LED drivers and I've never found one that didn't perform exactly like the known genuine samples I got from Maxim years ago. I don't know whether they're fakes or gray market 3rd shift parts or what but they work fine and they are affordable. If I had to pay what Maxim was asking I'd use something else.
dgtl:
I've had the same struggle with DS18B20-based sensors. As I needed ready-made sensors with wires attached, it was very difficult to find good ones. The whole world is full of the same stuff as sold on aliexpress, each having different kind of counterfeit chips in them. Even if they are kind-of-okay at 20C, then at 80C the readings are totally bogus, not even +/-5C. They have issues with parasite powering and are terribly bad at long lines with some noise.
Finally, I found one type of sensors, that so far have been precise enough and are digitally indistinguishable from real DS18B20 to believe that they actually contain the real chips (sensors with red-blue-white wires and red tag with black writing at wire end, about 4x more expensive).

One good indication of a real DS18B20 is scratchpad byte 6 (Reserved, non-constant). It seems, that this register is legacy from DS18S20 and it should read the same value for the same temperature readout and different values for different temperatures. So far, I havent found a clone, that would implement this register.
DrG:
I am impressed with the effort of Chris Petrich https://github.com/cpetrich/counterfeit_DS18B20 and decided to test out the ones I had on hand. Thought I would share the results (only one real surprise).

Ordered from Mouser:



8-D6-A1-E8-05-00-00-F6: ROM ok.
  Scratchpad Register: BE/01/4B/46/7F/FF/02/10/FE
  Info only: Scratchpad bytes 2,3,4 (4B/46/7F):  Maxim default values.
  Scratchpad byte 5 (0xFF):  ok.
  Scratchpad byte 6 (0x02):  ok.
  Scratchpad byte 7 (0x10):  ok.
  0x4E modifies alarm registers:  ok.
  0x4E accepts 10 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  0x4E accepts 12 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  Checking byte 6 upon temperature change: not necessary. Skipped.
  --> Sensor responded like a genuie Maxim.

Ordered from Mouser:



28-B8-47-0B-06-00-00-45: ROM ok.
  Scratchpad Register: C6/01/4B/46/7F/FF/0A/10/17
  Info only: Scratchpad bytes 2,3,4 (4B/46/7F):  Maxim default values.
  Scratchpad byte 5 (0xFF):  ok.
  Scratchpad byte 6 (0x0A):  ok.
  Scratchpad byte 7 (0x10):  ok.
  0x4E modifies alarm registers:  ok.
  0x4E accepts 10 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  0x4E accepts 12 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  Checking byte 6 upon temperature change: not necessary. Skipped.
  --> Sensor responded like a genuie Maxim.

Ordered from Banggood (this was the surprise)



28-8A-8B-C7-06-00-00-EE: ROM ok.
  Scratchpad Register: A3/01/4B/46/7F/FF/0D/10/CE
  Info only: Scratchpad bytes 2,3,4 (4B/46/7F):  Maxim default values.
  Scratchpad byte 5 (0xFF):  ok.
  Scratchpad byte 6 (0x0D):  ok.
  Scratchpad byte 7 (0x10):  ok.
  0x4E modifies alarm registers:  ok.
  0x4E accepts 10 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  0x4E accepts 12 bit resolution:  ok.
  0x4E preserves reserved bytes:  ok.
  Checking byte 6 upon temperature change: not necessary. Skipped.
  --> Sensor responded like a genuie Maxim.

All the ones below (from various export houses, Bangood, DIY, off of Amazon) were all:
--> Sensor appears to be counterfeit based on 4 deviations.








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