[SOLVED] DHT returns 00 01 93 ff ff ff ff ff ff

[LuCavallin]

Hello,
often my DHT sensor returns 00 01 93 ff ff ff ff ff ff with translates into NaN and NaN.
What is this value?

[RobertLucian]

Hi @LuCavallin,

Just to be really certain, can you show us a list with the values you get?
Say … a screenshot of your terminal.

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Coming back to your problem, the DHT sensor is know for having lots of noise on its lines.
When a NaN is read, this means there was noise down the line and the values couldn’t be read from the sensor.

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For this issue I have a solution for you that I’ve developed a couple of weeks ago.
Here are 2 topics that have as a subject the noise on the DHT lines:

• forum.dexterindustries.com/t/solved-dht-sensor-occasionally-returning-spurious-values
  Here you’ll find a nice scenario with some really nice graphs and explanations.

• forum.dexterindustries.com/t/noise-removal-algorithm-for-grove-dht-pro-sensor/2989
  Here is a more portable solution I’ve posted as a reply to the first topic.

Nonetheless, you also have access to this solution from within our GrovePi repository.
Here’s a link to the algorithm which helps reduce the noise between the DHT and the GrovePi:

• github.com/DexterInd/GrovePi/tree/master/Software/Python/grove_dht_pro_filter

Please try out some of those example programs and tell us how it goes.

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If there’s anything else that needs our attention, please inform us.

Thank you!

[LuCavallin]

Hi Robert,
I understood what the problem was - be ready, it’s rather stupid.
I was reading light and temperature concurrently

[RobertLucian]

Hi @LuCavallin,

I’m glad everything solved out.

The GrovePi library sometimes has some timing issues and because of this, I’d suggest you use locks when developing multi-threaded applications.

Thank you!