Author Topic: AM2302 / AM2302 in Bathroom Gets Stuck at 99.9% Relative Humidity  (Read 3310 times)


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I have encountered an annoying problem with the AM2302 and AM2303 series of sensors. I put one inside the bathroom fan housing in my master bathroom, and it reads the temperature and relative humidity in the room. Specifically, when the humidity gets above a set threshold, Venturii turns on the bathroom fan to expel the excess moisture in the air - typically from someone having a shower.

The first sensor I put in there was an AM2302 (white model) and it lasted for over a year without incident. Then one day, I noticed the bathroom fan was not coming on when it should, checked, and found that the sensor was reading 99.9% humidity. (Basically, maxed out.) I thought that it had perhaps saturated from a shower the night before or earlier in the morning, turned the fan on to help dry it off, and forgot about it. It never did restore, and I ended up replacing it with an AM2303 (grey model). I think they internally use a DS18B20 for temp but had the same humidity sensor. Anyway, it lasted for a month or so and then did the same thing. I checked the voltage this time, wondering if maybe it was too high or low - it was a bit low at 3.7 Vdc but this is the longest sensor run in the house, and I think I calculated by the cable numbers that this run is about 70'. I tweaked the power situation and brought it up to 4.9 Vdc when I replaced it a third time, a week ago.

Imagine my annoyance when I discovered that after only a week, the third AM2303 is now doing the same thing, pegging the RH output at 99.9%. Interestingly, the temperature readout is normal, and it's never spat out even one message that had a bad CRC check. Now I am stumped. I was going to set up another one of these in the other bathroom to perform the same task (fan control management) but I can't afford to keep replacing these sensors every week... Searching on the Goog doesn't seem to yield any results, which usually means that whatever my situation is [is] an anomaly and I must be doing something wrong. I've got two other 2302's connected to the same Venturii Sensor Acquisition (Prototype) Board and they have been working flawlessly for years, granted - in much lower occasional moisture environments.

Any ideas as to what might be causing these sensors to fail so rapidly? Is it just the moisture saturation that is killing [something] in the device that it never recovers? I've confirmed that they do dry out after each shower... Even after a few months in a box in the garage I hooked one up and found it still reporting 99.9% so it's definitely cooked. Is there a (better) / (more reliable) / (more resiliant in high moisture environments) sensor out there I should be considering?

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