grouping temperature sensors

Hello, as i am new to arduino this question might be silly but still... i have 5 diy aquarium LED lamps which i control with arduino. In the hood of each lamp there is a ventilator installed which is controlled (at the moment) by the simple timer. My idea is to connect the ventilators (12v) directly to arduino and to link them to temperature sensor. My problem is that i have a pre-programmed shield with one pin to connect ONE temperature sensor. I am thinking to do the following - to connect 5 temperature sensors in parallel (one in each hood) and to plug all of them to one pre-programed contact on a shield, like that i would expect the computer to receive a signal of a hottest sensor (without identifying which one is the hottest) and to start all the ventilators at once. The question would be - can it work like that? Can i simply group few temperature sensors and expect that ventilators will be on when any of 5 temperature sensors would exceed the limit safe temperature?

Hope my explanation make sense.

Can i simply group few temperature sensors and expect that ventilators will be on when any of 5 temperature sensors would exceed the limit safe temperature?

In general: no.

You forgot to provide links to the hardware you used (that "pre-programmed" shield as well as the temperature sensors). There is a myriad of possibilities of hardware in this area and we don't like to guess which one you might be using.

I am going to use DS18B20 temperature sensors. concerning the shield - i received it assembled with arduino mega board and touch screen and it is pre-programed to dim leds, control temperature etc. problem is that i have 5 lamps and only 1 pin ready to connect the sensor? I could put a sensor in one of 5 lamps but it might be that for some reason 5 lamps produce different amount of heat.

One pin is all you need for five DS18B20 sensors - or fifty. You are still not very forthcoming about the "Pre-programmed shield", but, if it is programmed to take the DS18B20, having them share a pin is likely to be what the programmer had in mind

It sounds like this is not a shield but a pre-programmed Arduino system. If it's programmed to read one temperature sensor you cannot just connect five and expect it to react on their maximum reading. Hardware-wise you're fine with with one pin if you're using the OneWire sensors but you have to change the programming. Was the system programmed with a DS18B20 or did it use another sensor type before?

Yes it was programmed with DS18B20. Normally the PC should control 2 heat sink fans with separate sensors and a heater-cooler with third watter temperature sensor. What i find confusing is that i have only one pin to connect 3 sensors??? Or is it only a matter of program? Can one define in a program to read different sensors through one pin?

Thanks.

You need to get au fait with the DS18B20. Read my previous and get the data sheet. The DS18B20 is more than just a sensor.

Can one define in a program to read different sensors through one pin?

Yes, you can. This kind of sensor uses a OneWire bus. This bus is designed to hold many sensors on just one signal wire (which also can act as the power wire). The sensors have addresses so you can choose in the program which one to read.

Ok now it make sense :) the only way is to rewrite the program to read 5 x DS18B20.

Honestly - is it doable for newbie? or should i better go back to a guy who wrote the original program and ask him to change it?

Thanks.

Do you have the source code of that program? Do you have some programming experience, preferably in C or a related language? It's not overly complex to change a program to read more than one sensor but if you have to state a clear "no" to one or both of the above questions, it's probably better to contact the original programmer.

Honestly - above mentioned sounds like a rocket science to me. I am afraid it means that i am better in cooking than programing :) and having in mind that my wife thinks i am an awful cook - i should better start looking for email address of that programmer :)

Thank you anyway.

jureivis: Ok now it make sense :) the only way is to rewrite the program to read 5 x DS18B20.

Honestly - is it doable for newbie? or should i better go back to a guy who wrote the original program and ask him to change it?

If you stopped being so secretive about this pre-programmed device, you might save yourself a bit of grief. Unless you won it in a side-show and are just wondering now what to do with it, there must surely be some information about it that prompted you to get in the first place, and yet you won't even tell anybody about that.

It is very likely that, if this mysterious device is pre-programmed to use the DS18B20, it will be capable of using several. In that case, you are good to go, no re-programming required. If not, try the programmer but who would know what your chances are there? A little bit of intelligent communication here instead will probably resolve this matter, one way or the other.

I submit it is more likely that this device isn't pre-programmed at all. It sounds rather like some sort of starter kit that is capable of being programmed "to dim leds, control temperature etc." but, as it comes out of the box, can't actually do anything. In that event, you've got something everybody else can understand, and could be just what you need.

If you can't resolve the matter sensibly, and it really is a single purpose pre-programmed device, you might as well try your luck with leaning five sensors against it, secure in the knowledge that the only alternative is to treat it for what it then probably is - something to be hacked for salvageable parts - parts that will be useful for you start over again. And yes, honestly, it is doable by a newbie. There will be plenty of support for you on this forum.

All you need to know is here:

http://www.hacktronics.com/Tutorials/arduino-1-wire-tutorial.html

Hello,

thanks for the link. What concerns the secret shield :slight_smile: it is not that i am hiding something - just not sure what is it. Here i attach the file with each pin explained (i received it with device)

!(http://C:\Users\SIGITAS\Desktop\PRIVEE_2013\reef\kompas\shield v3_5 connection_full.pdf)

you can see that there are 3 sensors connected to the same pin. What harm can i make to a device if i connect 2 more sensors just to try??? Also the picture of a device itself to make it less mysterious :slight_smile:

Thanks for help.

shield v3_5 connection_full.pdf (43.6 KB)

jureivis: it is not that i am hiding something - just not sure what is it.

Well there is probably no surprise about that. I suspect the only people who know what it is are the original manufacturer and the original person who was supposed to receive it as what I imagine is a replacement module, which isn't you.

While the device is about the size and shape of a shield for an Arduino it clearly isn't one and has nothing to do with Arduino. It appears to be part of the controls for a refrigeration system.

What harm can i make to a device if i connect 2 more sensors just to try

In the highly unlikely event that you can make it work with three DS18B20s, you can very probably make it work with five. You certainly won't do any harm but it seems the speculation in my previous was right - it's something to be hacked for spare parts.

While the device is about the size and shape of a shield for an Arduino it clearly isn't one and has nothing to do with Arduino. It appears to be part of the controls for a refrigeration system.

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It is certainly at least Arduino compatible because it is mounted on Arduino Mega (it is not visible in the picture but if you have doubts - i can make a picture of a back side of device). And what makes you doubt that it could work with 3 sensors? In a scheme attached (pdf) you can see three sensors plugged ???

If you want to change anything in the current configuration you probably need the source code of the program that currently runs on the Arduino. The drawing shows three sensors connected to the OneWire bus but we simply don't know how much the software supports. We already knew that the hardware supports multiple of them, so it's all about software.

jureivis: It is certainly at least Arduino compatible because it is mounted on Arduino Mega (it is not visible in the picture but if you have doubts - i can make a picture of a back side of device).

Apart from the words "Mega power supply", which could be meaningless, there is nothing on the data sheets that even vaguely suggest it has anything to do with Arduino, and quite a lot which suggests it hasn't - .like 48v wires. Information on how it connects to Arduino would be more informative. You really need the programme that is in it too but, once you have sorted the connections out, you might be able to write a new one. I believe the screen is one popular on Arduino, so there should be no problem with that.

And what makes you doubt that it could work with 3 sensors? In a scheme attached (pdf) you can see three sensors plugged ???

I don't doubt it will work with three sensors. I do doubt you are going to get it to work - with any - but, if you do, it is likely to work fine with five. This would surely be the case if it polls the DS18B20s by index rather than stored addresses.