Hi,
According to DHT11, the sensor can be powered from 3.3V to 5.5V.
I've connected one to a dual voltage board and notice a 10% gap in hygro value (45% under 3.3V, 56% under 5V).
The temperature read the same.
Would you have any explanation about this gap? Is my sensor defective somehow?
Thanks for any hints
The DHT sensor series are not that accurate in humidity (~5%) and I do not know how the internal sensor works, but if some R.C. is at heart it might take more time to reach some voltage causing a different value.
just guessing
How long is your cable. Just found this on the datasheet.
When using a 3.5V voltage supply cable length shall not be greater than 20cm. Otherwise, the line voltage drop will cause the sensor power supply shortage, caused by measurement error.
Thanks for the indication. The cable was ~30cm between the sensor and the board. I reduced it to <20 (~15cm) but the results remain similar, showing a msignificant gap between 5V and 3.3V reading
How frequently are you reading it. I noticed in the blurb somewhere, that it's particularly slow sensor. Not capable of more than 1 read per second.
I'm using the AdaFruit's DHT library example code for this experiment. There is a 2 seconds wait between reads. Increasing it to 5 seconds doesn't change the outcome.
on this page - DHT11 Humidity And Temperature Sensor Package | Hackaday -
it shows that the DHT11 needs 3.5 Volt. That is a minimal difference.
Can you try the DHT11 at 3.5 4.0 and 4.5 Volts ? and put results in a table?