Interfacing

raspberry read temperature from DHT11

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tosiara  
Right now I have connected 10K resistor and there seems to be a progress. Still "Sorry! Sensor dosent ans!", but at least the program does not hang. So I will try to find 4.7 and give a try
Thanks!

Connecting a pull-up resistor is very important.

Edited by actkk2000 at Tue Nov 4, 2014 15:51

And remember to use 3.3V instead of 5V.
At least it worked that way for me...

Did you checked if the CPU frequency is not simply to low ? Because if it is idle, the frequency is reduced to save energy but it is known to create issue for usleep()

Yes, low frequency may be an issue as well, it is often mentioned for DS18B20:
http://forum.lemaker.org/forum.p ... 72&fromuid=1602
http://forum.lemaker.org/forum.p ... 57&fromuid=1602
http://forum.lemaker.org/forum.p ... 22&fromuid=1602
In my case the governor is set to "fantasy", and I never saw frequency below 720 mhz, not sure that is correct...

tosiara  
Edited by tosiara at Wed Nov 5, 2014 02:33
Connecting a pull-up resistor is very important.

I have tried 4.7K and 10K resistors - did not help
And remember to use 3.3V instead of 5V.

I'm using this sensor: R1B1 DHT11, in tech specs it has "Working voltage: DC 5V". Anyway, I tried connecting to 3.3V - did not help
Did you checked if the CPU frequency is not simply to low ?
  1. # cat /sys/devices/system/cpu/cpu1/cpufreq/cpuinfo_cur_freq
  2. 720000
Copy the Code
On this board I have also connected DS18B20 with 4.7K resistor - and it works fine

Is there a way to check - what is wrong? Like, is the sensor working, maybe it is broken?

Did I connect correctly?

I've used PIN7 (GCLK) for my DHT22 : that was the default port for the program I used

Except that I've the same connection

tosiara  
seblucas replied at Wed Nov 5, 2014 03:03
I've used PIN7 (GCLK) for my DHT22 : that was the default port for the program I used

Except that I ...

seblucas, can you share which code did you use?

tosiara  
Edited by tosiara at Wed Nov 5, 2014 06:05

I have flashed Raspbian 3.1 - and all works perfectly (5V, with and without resistors)
So it is something with Lubuntu 3.1 and WiringBPI I used before.

tosiara replied at Wed Nov 5, 2014 08:59
I have flashed Raspbian 3.1 - and all works perfectly (5V, with and without resistors)
So it is some ...

Good to know!

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