multisensor inputs?

Good evening! :) I need to measure temperature into a building and out of it, detected at the same time with two sensors. Is it possible to do with Arduino? In a broader view, how many input devices (sensors) is possible to connect to Arduino? Thanks for your help ::)

how many input devices (sensors) is possible to connect to Arduino?

The Arduino has 6 analog inputs. If you're willing to put up with the loss of precision, you can use analog multiplexer chips to fan those out to several dozen.

For temperature, you can use sensors like the DS1820 series, and get several inputs on a single digital pin.

So, at least in theory, the answer is "more sensors than you can afford to buy" ;D


;)Many thanks, Ran! Now, it's time to deepen my knowledge on "analog multiplexer chips" and before on connection between Arduino and sensor. Christmas holidays are a good opportunity ;D RickyB

You should be aware that there are limits for the length of wire you can have between your Arduino and your sensors and still maintain reliable meassuring.

This distance will depend on the sensor, but you shold make sure you know the details for the sensors you choose.

Hi rickyb at present time, i have 4 DS18B/S20 temp on a long 40m ethernet cabel. on one out af 4 OneWite strings. 3 on the sec. 30m ethernet cabel. Also one wire. the last 2 is not in uses right now. also in the ethernet cabel is 2 output pins to use at the fare end. And 1 input pin (Int 1) to let the system know i somthing like to talk to the system.

Its all buit on MEGA and ethernet shield. The shield i am make will containe 2x 24LC512 EEPRom for name storing of the onewire devices (+ a lot of other text and setup and other use in time) and a SD card for webpages and log. And the 4 Strings for OneWire.

Thanks to MikMo for the indication on relation between distance and precision. In choosing criteria for Sensors I will check this :)

I would like to know something more about aim7100 work. If I got it properly, you use several sensors (4 + 3 ?) connected through an ethernet wire with 4 strings and two of them are not used right now. Do you think would it be possible to use them for other variables (let's say "light" or "humidity" for instance?) Eprom and SD card are used to store data that you can download to your PC and analyze. Is that right? The choice to have several sensors is related to the need of making an average of the temperature detected?

For all of those who will kindly help me, sorry if those questions will sound banal to you, I am still in the stage of learning as much as I can on the possibilities of Arduino for environmental variables monitoring purposes. In the meantime I am practising with Arduino "Getting started" and "Experiments" ;)

Hi rickyb

I will try to explane my project for you the best ican (My english is not so good.

I have 4 string, witch are a RJ45 connecter, on eatch of the string i have 2 output and one int, and also a onewine pin, 5v and 4 gnd. On the one wire i can have many one wire devices, if only the component is one wire you can connect it to the one wire.

At preset i have 4 on one string and 3 on a other string. my goal i to have 5 temp (DS18B20 / DS18S20) on eatch string. a total off 20 (DS18b/s20), but i also what oter one wire type in the future like a 4x20 lcd display to sent information to.

As now i have dump the SD cart, i just use my server to poll for data eatch 5 min, and then store the data on MYSQL server.

I use eeprom to give eatch string and eatch one wire device a name instate of the ID eatch one wire device have.

Ican alway see any given data from the DS18b/s20 on a web page on the MEGA and ethernet shielt.

I am maken a home control center, and i time, there will be door censor, temp in eatch room of my house, hov my heating system i doing and so on. Even wind speed and direction. How aboute the greenhouse, do it need to water the plants, do it need to open windows and so on. Its a complex system. And iam am only make it in my spare time.

Iam also new to program in C, iam a pascal man, but hay, like to learn new tings :-)

Hope you can read it :-)

Good morning alm7100 :) Your system is capable of great things!!! The complexity of your project suggests to me a lot of study and application. I have in mind a system to detect parameters linked to environmental quality, partly similar to those you are already recording. If you agree, let's keep informed on future stage of our projects. Thanks for your post :) :)


You can get the code iam workink on, keep in mind that this is work in prograss and its my first c program. :-)

I downloaded the zipped file and expanded it to HCC.pde. I click on it, arduino sw opens but it appears a white page. I will try again. Many thanks
RickyB :slight_smile:

I succedeed. It is readable now.

Nice, hopes you can se witch pin is for what :-)