Maximum cable lengths for Dht22 and TMP36 Sensors

The Dallas 1-Wire devices (DS1820, etc) will repay study if you want 12 sensors in the room.

They will need to be daisychained, not connected via a star topology... but just three wires from host, to sensor0, to sensor1....

For rapid development, you may want to start this project with a PC rather than an Arduino, as host... but once various things ironed out, the Arduino could be "trained" to do the work.

Very non-trivial... but 12 sensors in inherently non-trivial, and a little work to get started with 1-Wire will repay you with years of being able to do many fun, or at least useful, things.

The following is mine, a mish-mash of imperfect early efforts and more recent, more informed articles....

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In the Arduino world, we often just put a single sensor on an Arduino pin, and thus get around the issues of "addressing" ONE of several chips on a MicroLan. You can, in theory, "talk" to many (100?) 1-wire chips... temperature sensors and more... using just one Arduino pin... but to do that, you have to master "advanced" 1-Wire concepts, beyond those used by Arduino/1-Wire users.

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Thanks a lot tkbyd. That's really helpful to me and it looks like your content is a great place to start.

Appreciated.

On the DHT22 transmission distance question, 20m according to this document http://cdn.shopify.com/s/files/1/0045/8932/files/DHT22.pdf?100745

I have one operating quite OK over 25m of CAT 5 cable

Hello
I´m quite new to arduino.
I was also wondering of max cable lenght....
so I made program which read from data pin (of same dht22) to two different pins of arduino. Wires to one pin were short to other pin were connected through 60m of UTP.
temperatures were same....
Sorry for my english, it´s not my first language

PS: for pictures DOLGE_ ZICE means long wires, kratke zice/short

thanks akaj9!

60 Meter is a very nice distance!
(and your English is OK too! what is your native language? Slovenia?

@robtillaart
Yes my native language is slovenian. How did you assumed that it is?

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akaj9:
@robtillaart
Yes my native language is slovenian. How did you assumed that it is?

DOLGE ZICE kratke => into google translate autodetect mode => :wink:

akaj9:
Hello
I´m quite new to arduino.
I was also wondering of max cable lenght....
so I made program which read from data pin (of same dht22) to two different pins of arduino. Wires to one pin were short to other pin were connected through 60m of UTP.
temperatures were same....
Sorry for my english, it´s not my first language

PS: for pictures DOLGE_ ZICE means long wires, kratke zice/short

Thank you ... Thank you very much akaj9...
I've tried anything but nothing works....
With your picture, I can reach 150m of UTP Cat 5E.

You save my life !!!! LOL...
Thank you akaj9

Hi,

I'm looking into which humidity sensor I should use for my project and the DHT22 looks to be an option. (Which humidity sensor should I use? - Sensors - Arduino Forum). The sensors are located up to 10m from the Arduino.

Do I understand from previous posts here that the the DHT22 signal can be transmitted 60m+?

Thanks

Ron

JonRon:
Hi,
...
Do I understand from previous posts here that the the DHT22 signal can be transmitted 60m+?
...

seems to be so,

I don't care if I need to buy new sensors. I'd rather not have to buy more micros.

Arduino pro mini is cheaper than a dht22.

akaj9:
Hello
I´m quite new to arduino.
I was also wondering of max cable lenght....
so I made program which read from data pin (of same dht22) to two different pins of arduino. Wires to one pin were short to other pin were connected through 60m of UTP.
temperatures were same....
Sorry for my english, it´s not my first language

PS: for pictures DOLGE_ ZICE means long wires, kratke zice/short

HI, akaj9 I'm from Macedonia, I recognized your language without google translate :slight_smile:
I have a project that I need to connect 5 DHT22 sensors on One Arduino UNO... 2 xDHT22 are on 15m distance 2xDHT22 are on 7m distance and 1xDHT22 is on 1m distance
I was wondering how should I connect them...
is it like this: inside UTP cable there are 8 wires... my DHT22 has "+","-","s" ... so I'l connect 2 sensors on one UTP and I will have 2 wires left out ?

Or did you connect all 8 wires to one pin (s) on the sensor... this is my dilema?

I gess it is the first option, but i'm not sure.

And my other question is about powering all system... will the 5v power on Arduino Uno be enaff, or should I put more power for instance like separate power to sensors
Thanks

According to Adafruit Data sheet for the DHT22, it can transmit up to 100 meters https://www.adafruit.com/datasheets/Digital%20humidity%20and%20temperature%20sensor%20AM2302.pdf

I was researching this "Distance Thing" with DHT11, DHT22 and DS18B20 devices. I believe they are all "1Wire" devices and this paper came up.

It got more technical than I could handle about all the different permutations and caveats, but to summarize (optimistically) it said: 200M is pretty easy with just a pull-up resistor. If you wanted more, you needed some extra circuitry... but it got to 500M.

200M was far more than I needed, so I didn't bother reading further. :slight_smile:

michinyon:
Arduino pro mini is cheaper than a dht22.

Although you're correct, by the time you get a $1 power supply, and some kind of communication gear (say ESP8266) at each node you've exceeded the price of the DHT22.

And I prefer the KISS principle, we can run one pair of wires (at least the DS18B20 supports parasitic powering) to every room in the house with 200M (my house several times over) :slight_smile:

So, why am I having trouble reading DHT22 with 12m of cat5e cable?

  • I'm running the +5V and gnd via the same cat5e cable as the return signal ..
  • I'm sampling each 5 minutes
  • sensor is OK, i have two of them, the other is connected with 0,5m cable and the reading are OK on this one .. already tried to swap them, so the sensors are ok .. they are just sensors, without board ..
  • tested the cables and they seems to be ok, i also get +5,3V on sensor side so i guess it's not voltage-drop related ..
  • tried with and without arduinos internal pull-ups ..

Most of the time I get timout error .. with unplugging-replugging I've managed somehow to get a couple of hours OK readings but then again time-out ..
What am i missing here? Is the problem in long power cables? I should put signal and gnr on twisted pair, right? Should i use pull-up resitstor on sensor side too? Or do need to include a capacitor to filter some noises?

Loosing my last pieces of hairs on this one, since everyone else seems to get ok readings with even longer wires and no extra components ...

Hi all,

So just to be sure before I start running cables through my entire house before plastering, your all running two sets of CAT5e cables to each sensor, one goes directly to the sensor the other your using for power, which loops between sensors.

Anyone have any ideas with regards to connecting 46No. DHT22 sensors. Distance's range from 1-35m. Its part of a monitoring system for MVHR and damp proofing solution.

I'm unsure about what cables to use CAT5e? 46 of them drawing power through one cable, will that be to many? Should I use standard twin & earth for the power instead?

900m long cable for DHT11 or 22 sensor. I found this great solution, and works for me :slight_smile: Here is the link: SPECTRA

pylon:
For the TMP36 definitely not,
The TMP36 is an analog sensor and this signal will take up lots of electrical noise even if the cable is only 1 or 2 meters. You won't get a usable value with long cables even if you put some caps in place to filter out some of the noise.

Directly connected yes 12 meters are too long

But if you read the datasheet it is possible.
See : This brief visual dictionary of mech. engineering terms! cam, chamfer, etc... - #2 by Robin2 - Bar Sport - Arduino Forum
You will see I realize good measurements with a LM35 and 50 meters cat5 cable.

I have only LM35 datasheet extract :

Hi,
this is my first post in the forum, after just few days of playing with Arduino.
Today I made a test with DHT11 sensor (attached to a mini board like that: https://goo.gl/images/2QgXr9) on a 50m long UTP cable. It worked perfectly fine, I got no false readings, the readings didn't differ at all when the sensor was connected to Arduino via short jumper cables.
I noticed that on the mini board, there is a capacitor and resistor (though I don't know the exact values of capacity and resistance), maybe that helps for long distance reads.
Regards,
jjankos.