STATEMENT
As convenient as the DS18B20 is, the long-term reliability of these sensors is often a bit overestimated in real installations. It’s not “just a sensor,” as someone once commented somewhere — well, maybe in their world it is 
. In many projects they work perfectly at the beginning, but after some years of continuous operation read errors tend to appear more frequently. That observation is actually one of the reasons why I started this article series: DS18B20 Wrong Readings (85°C / -127°C) – Reliable Fix and Robust 1-Wire Design
In my view this has less to do with the electronics itself and more with the real-world environment the sensors are exposed to. In this particular case an electrically noisy environment was excluded as a factor, but bus noise can still be a major source of intermittent problems in many installations — even with brand new sensors.
Depending on the installation, typical lifetimes seem to be roughly in this range:
- TO-92 in free air: about 10–20 years (from literature)
- Cheap stainless-steel probe versions: about 2–5 years (own experience)
Especially in humid environments (e.g. hot-water tanks, boiler rooms, outdoor installations), moisture can slowly penetrate the assembly or migrate along the cable. At least to me that explanation sounds plausible, and it would also explain why sporadic communication problems may occur long before a sensor finally fails completely.
Because of that, it can be useful to think about robustness in the sketch from the very beginning, for example by implementing:
- a Recovery and Escalation Strategy DS18B20 Error Handling – Recovery and Escalation Strategy for Unstable Readings
- Logically Safe Usage / Fail Safe concepts DS18B20 Fail-Safe Temperature Reading – Safe Values When Sensor Data Is Invalid
- or at least a simple Optical Feedback indicator (this topic)
At first this might look unnecessary — often one is just happy when the system finally runs at all. But with increasing runtime it can help to keep the system stable and gracefully handle aging sensors.
Of course anyone is free to ignore what I’ve posted so far. But in projects that are expected to run for years in the real, wet, dirty world — where nobody treats the hardware gently (think of equipment in a stable being sprayed with water, for example) — failures will eventually happen.
So no, this isn’t coming from an ivory tower perspective.
A typical application for me — for example a pipe heating system that prevents a water pipe from freezing with minimal energy — would look something like this:
A solid, properly sealed and grounded aluminium enclosure with exactly four well-sealed openings:
- power in
- switched power out
- one sensor cable
- one LED that tells me everything I need to know about the system state
I also don’t need overly complex code that I won’t even understand myself a month later.
The system simply needs to do its dedicated job with maximum reliability — and under no circumstances become a hazard!