Bought some 18b20 temp sensors on ebay. Are they fake? or am I doing something wrong?
- Thread starter Gibbedy
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PaulStoffregen
Well-known member
Did you use a 4.7K resistor? It's required, but I don't see one in your photo.
In fact, I can't see if you're connecting this to Teensy or anything else. You're using the OneWire lib, right?
In fact, I can't see if you're connecting this to Teensy or anything else. You're using the OneWire lib, right?
Originally was all connected up to teensy with 4.7k pull-up.
All info was in image.. Basically with 5v power supply only connected, my 18b20 is a dead short.
Acts like a forward bias diode.
I have 20 of these in a bag that all do same thing.(4 I've tested so far do anyway)
I believe the picture of my gnd&vdd wiring is correct as per data sheet.
Maybe package is reversed? However the test code does not work that way in any case.
Have I understood what you are saying correctly Ben?
Ben
Well-known member
Yes, you did. I also rechecked your picture and the Datasheet, and it looks right to me, too. Maybe you are right with the package reversed, but if that's the case your ICs are very likely a fake, I can't imagine this passing through maxim's QA.
Constantin
Well-known member
Probability that these are real or maintain the same tolerances re accuracy as Ti/Dallas/Maxim hardware are pretty much nil. That's the issue with buying gear from eBay.
Given that people go as far as faking lm7805 voltage regulators, I could see why faking a far more expensive component like a DS18B20 would be enticing.
Given that people go as far as faking lm7805 voltage regulators, I could see why faking a far more expensive component like a DS18B20 would be enticing.
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I got refund pretty quick.
Edit: Just in case there was any doubt... genuine ones I purchased work fine in same circuit where the fake ones did not.
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