I use a DS18B20 temperature sensor IC in several of my projects and I encountered an interesting problem recently. This IC runs over Maxim’s 1-Wire interface and should, in theory, work over cable lengths of several hundred meters or more.
However, when I tried to run one of these sensors over a cable longer than around 50cm it refused to work. Shortening the cable always brought the sensor back to life.
In desperation I tried a different sensor and hey-presto, it worked on my test 5M cable.
So, I purchased 10 sensors off EBay and gave them a try. Each one worked perfectly on my 5M cable so I can only assume that I’d been unlucky to have a semi-faulty sensory IC.
I’ve binned this IC as whilst they are rather expensive if you buy from a regular supplier, at less than £2 each off EBay, I wasn’t going to risk having the IC suddenly fail on my at some point in the future; and there’s obviously something wrong with it.
However, when I tried to run one of these sensors over a cable longer than around 50cm it refused to work. Shortening the cable always brought the sensor back to life.
In desperation I tried a different sensor and hey-presto, it worked on my test 5M cable.
So, I purchased 10 sensors off EBay and gave them a try. Each one worked perfectly on my 5M cable so I can only assume that I’d been unlucky to have a semi-faulty sensory IC.
I’ve binned this IC as whilst they are rather expensive if you buy from a regular supplier, at less than £2 each off EBay, I wasn’t going to risk having the IC suddenly fail on my at some point in the future; and there’s obviously something wrong with it.
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