fake chips, last part ?
In November 2018 I purchased a couple of LM35 temperature sensors from ebay. These are in a 3 lead TO-92 package and look like a transistor. One lead is power, another is ground and the third is a voltage output, 10 mV per degree Celsius. I had been using the LM34 temperature sensor with the same pinout but which has a Fahrenheit output so I wanted to try the Celsius version.
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| who can tell just by looking if it's a fake ? |
These were my notes at the time: " tried one, got hot (smoke), then tried an LM34, it was OK "
I tried plugging the other one into one of those LCD based component testers, it indicated it was a dual diode, so not even a transistor ?
In other words, it's FAKE. Three strikes and you are out ! No more trying to get bargains on ebay. I did get my money back but yikes, smoke ! It's one thing to have something fail but another to actually be potentially dangerous !
BTW this is another chip that is out of stock at both Digi-key and Mouser (LM35DZ/NOPB), they are $2.49 but won't be available till 2023 !
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| can't buy them if they don't have them, that's the lure of ebay sometimes, ebay seems to have them |
I also saw a thing on the internet:
where the fake lm35 is really an LM335. Not in this case. When hooked up as an LM335 the output is about .6 volts or about what would be expected from a forward biased diode. When the fake LM35 is touched, the reading goes DOWN as would be expected from a diode.
Best Regards,
Chuck, WB9KZY
http://wb9kzy.com/ham.htm