Fake DS18B20 sensors from China sold on Ebay / Amazon?

A while ago I read an article on fake electronic components that are flooding the market with high end audio and hobbyist parts being the biggest targets of the fakers. The article in particular spoke about high end transistors used in power amplifiers blowing or producing nowhere near the gain and / or frequency response expected.

It turned out to be cheap transistors packaged and stamped with a high end part number; sure it worked as a transistor but you wouldn’t want to use it in any equipment as it would likely fail. The popular 2N3055 transistor was also a common transistor made by the fakers which turned out to be a small signal transistor die placed in a TO-3 package. It didn’t say where these were purchased from but clearly they had entered the supply chain from the far east.

Do any search on google for fake ICs and transistors on ebay and you will see what I mean. Even microcontrollers have been faked. Yes there are even fabrication plants that copy genuine parts and mass produce them. These chips often will work OK but do have some problems or do not perform as expected.

Alternative to cloned chips are ones that are something completely different and have the tops sanded off, ‘re-capped’ and then stamped with a totally different number. All the chip has in common is that it has the same number of pins. Sparkfun received some counterfeit Mega 328’s article here which seems crazy really. Why would a company go to the effort of repackaging chips, stamping them with a incorrect part number and then pass them off as the genuine article. It’s clear these won’t work. But it happens.

The third thing is a lot of chips have been desoldered from scrap boards and passed off as new with no ESD protection so many of these are dud on arrival.

I knew there were fakes in China but I didn’t realise it was to this extent until it happened to me. I bought some DS18B20 digital thermal sensors off ebay for a cheap price. Now I’ve been buying components from ebay for a while and not had any problems but these were fake. I could not get them to work in one wire mode (parasite mode) however they would work when bus powered albiet producing wildly inaccurate readings. All of them had the same serial number and a google search showed that someone else had the same problem and his were stamped with the same serial number and date code as mine.

I put a complaint in to ebay and got my money back. So with the minimum order from Digi-key being a problem as I didn’t need anything else I bought some from Amazon. To my amazement these were also fake. Three out of the five had the same serial number and the other two were the same as each other. Another google search proved these to be a fake part.

I left a negative review and decided to use them anyway throwing away two that didn’t even work at all (they smoked when powered or could not be detected) but used them in bus powered mode and altered my code to compensate.

Here’s what I did:-

if (millis() – lastTempRequest >= delayInMillis)
temp = sensors.getTempCByIndex(0) – 1; // added -1 degree to end to account for inaccuracy of chinese fake DS18B20
lastTempRequest = millis();

As you can see just adding a -1 to the end of the instruction to get the temperature from the sensor will drop the produced reading minus one degree for example if the real temperature is 22 degrees the sensor would read 23 degrees (depending on how inaccurate it is) so you would add -1 to compensate. Of course you would need an accurate temperature probe for this.

An ATMEGA168 based temperature probe using a real DS18B20

It so happens I made such a device but I used a sensor attached to a cable – this isn’t fake but was bought from ebay. It’s a simple device using a 7 segment display showing temperature from 0 to 99 degrees C and powered by a ATMEGA168.

Just goes to show – don’t use ebay / amazon if you are building serious projects. Use a reputable supplier such as Farnell, Digi-Key or Mouser.

Cheap isn’t always cheerful.