DHT22

CharlyDelta

time import sleep import Adafruit_DHT DHT_SENSOR = Adafruit_DHT.DHT22 DHT_PIN = 4 while True: humidity, temperature = Adafruit_DHT.read_retry(DHT_SENSOR, DHT_PIN) if humidity is not None and temperature is not None: print("Temp={0:0.1f}*C Humidity={1:0.1f}%".format(temperature, ...

michelvallee

... RPi ne chauffe pas. L' autre méthode est de brancher tes capteurs sans fils ou avec des arduinos en RS-485. J'ai un exemple de capteurs DS18B20 et DHT22 sans fils avec un nrf24L01. Cela fontionne sur batterie environ 6 mois avec des AAA. https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=104359&p=1158447&hilit=shockburst#p720838 ...

michelvallee

Bjr, DS18B20 j'en ai fait fonctionner avec 30m de cable (cat5) et en mode parasite en + DHT22 le datasheet dit 20 m https://cdn.shopify.com/s/files/1/0045/8932/files/DHT22.pdf?100745 J'ai un DHT11 en 5V avec 3m de cable pas essayé + Très bonne distance... À part les ...

totoharibo

petit problème de compatibilité : DS18B20 et DHT22 sont en 1Wire
le SW-420 est une sortie numérique donc ne peut être mis avec les autres
le SW420 tu n'en parles plus, c'est HS ?

danjperron

... RPi ne chauffe pas. L' autre méthode est de brancher tes capteurs sans fils ou avec des arduinos en RS-485. J'ai un exemple de capteurs DS18B20 et DHT22 sans fils avec un nrf24L01. Cela fontionne sur batterie environ 6 mois avec des AAA. https://www.raspberrypi.org/forums/viewtopic.php?f=44&t=104359&p=1158447&hilit=shockburst#p720838 ...

JumpZero

Bjr,

DS18B20 j'en ai fait fonctionner avec 30m de cable (cat5) et en mode parasite en +
DHT22 le datasheet dit 20 m https://cdn.shopify.com/s/files/1/0045/ ... pdf?100745
J'ai un DHT11 en 5V avec 3m de cable pas essayé +

michelvallee

... de la piscine (Baoblaze DS18B20) - Détection de l’arrêt/démarrage de la thermopompe (SW-420) - Température extérieure et taux d’humidité (DSD Tech DHT22 AM2302) La particularité de mon projet est la distance entre le PI et les senseurs puisque le PI est localisé dans ma remise à environ +/- 10 ...

adellis

... Id reported by the Python (96 in this case). I call this once at the start and then use the check to decide whether to read from the BME280 or the DHT22. Thanks for all you help.

adellis

... works fine with no BME280 connected, it just reads zero values. I was hoping something would report an error so I could fall back to using the DHT22 which is connected. I've tried a raw open("/dev/i2c-1") and then an ioctl on the I2C_SLAVE with the BME280 device id and that doesn't fail either. ...

CharlyDelta

Now I want to get temperature and humidity (from DHT22) printed in the camera page web beside the date and the hour. How can I do this ?? Easiest way to do this is to periodically write out the temperature and humidity to /dev/shm/mjpeg/user_annotate.txt ...

Kirikou_iot

I'm looking for someone I can pay for a basic project...Smart agriculture with Lora raspberry pi
Collect data with sensor (DHT22, ....) and send to Lora Gateway

adellis

... work is when the sensor isn't connected. The program still opens the file descriptor as if everything is fine, when I want to fall back and use a DHT22. The ic2detect -y 1 shows 0 1 2 3 4 5 6 7 8 9 a b c d e f 00: -- -- -- -- -- -- -- -- -- -- -- -- -- 10: -- -- -- -- -- -- -- -- -- -- -- -- -- ...

ras07

Now I want to get temperature and humidity (from DHT22) printed in the camera page web beside the date and the hour. How can I do this ?? Easiest way to do this is to periodically write out the temperature and humidity to /dev/shm/mjpeg/user_annotate.txt ...

CharlyDelta

Ok... now I can get motor working good,

Now I want to get temperature and humidity (from DHT22) printed in the camera page web beside the date and the hour.

How can I do this ??

Thank you for your help.

hippy

... more time than most analysing exactly what the true situation is as best they can tell. Including Craig Ringer. His work has mostly been with DHT22's but I have seen references which suggest what he has discovered also applies or helps with DHT11 and others - http://blog.ringerc.id.au/2012/01/using-rht03-aliases-rht-22.html ...

RichardRussell

... (roughly) the mis-read rate, which is useful but still means retries are regularly required (and you have to wait at least a second - two with the DHT22 - before you can do so). My guess is that the worst case latency variation is just too great to guarantee recovering good data. But I know Hippy ...

RichardRussell

The DHT22 needs to be supported in the code Indeed, and it is! I've REMmed out the lines for the DHT22 in the code I posted; in principle it should simply be a case of disabling the DHT11 line and enabling those two lines, ...

bensimmo

... end of the stick, I thought you were trying to poll faster than it would allow, and/or worry about the heating effect at 1second polling. The DHT22 needs to be supported in the code though as it's the newer device. I was just thinking the 2second interval might be extra calculations and not ...

RichardRussell

DHT22 may well be sampling differently to give it it more accurate measurement ? I don't think the DHT22 comes into this (what I have appears to be a DHT12, not a DHT22). The DHT22 is significantly different from the DHT11/12; ...

bensimmo

... to make it easier to get a reliable reading. Both components are quite large. It probably the ADC whatsits that's limiting the reading rate. DHT22 may well be sampling differently to give it it more accurate measurement ?

RichardRussell

My BBC BASIC interface to the DHT11 (or DHT12, DHT22) works, but it's far from perfect: Sat. 1 Jun 2019,21:31:58 Humidity = 15.0%, temperature = 34.8C Sat. 1 Jun 2019,21:32:00 Humidity = 15.0%, temperature = 34.9C Sat. 1 Jun 2019,21:32:02 Humidity ...

hippy

... limit on read rates in the datasheet I have. It states here that for the DHT11 "No more than 1 Hz sampling rate (once every second)" and for the DHT22 "No more than 0.5 Hz sampling rate (once every 2 seconds)". I have to agree it says that, but there's no indication I could find of what the basis ...

RichardRussell

hippy wrote: ↑
Sat Jun 01, 2019 12:12 am
I couldn't see any limit on read rates in the datasheet I have.

It states here that for the DHT11 "No more than 1 Hz sampling rate (once every second)" and for the DHT22 "No more than 0.5 Hz sampling rate (once every 2 seconds)".

John_Spikowski

I wish I had the knowledge needed to do a start from scratch effort. All I want to do is get a stable GPIO extension module built and able to communicate with common used sensors.

DHT11 Resource

bensimmo

... iirc has some c code. also a direct attempt at a kernel implementation, might be easier to read what is happening ? https://github.com/edwardlintw/DHT22

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