I have seen some Instructables on how to use the Arduino as a Thermostat. Basically a LCD is connected with some Push Buttons to set the High and Low Temp thresholds and a Probe does the measuring.
My question is if I have 5 appliances for example and I want to measure and control the temperature of each appliance separately, would I need to have 5 separate Adruino boards or can I connect 5 X Probes + 5 X LCD's + 5 X whatever else is required to 1 single Arduino Board and the program the arduino to control each appliance temperature separately?
Depending on what kind of device you are using to read the temperature, you might, or might not, be able to connect more than one of them to one Arduino.
You can certainly connect 5 transistors to control 5 relays to one Arduino.
The program is the least of the problems. The program would just be subroutines called for each appliance you have connected.
The problem will be I/O count. You don't mention details on your hardware, so it will be up to you to figure out how to connect the 5 X probes, the 5X LCDs, and the 5 X whatever else to the arduino. I suggest looking into serial interface (I2C is not too far apart) for the LCDs smart addressable sensors (DS18B20 or sensor with addressable interface like ADC1115 board), and I/O expanders (again if not too far apart PCF8575 on I2C)
as with all things, the answer is .... it depends.
if you have a shelf in the kitchen with the coffee maker and a toaster oven and you have a soldering iron in the shed. the distance determines that you need at least one board for each.
but, if you have a shop bench with a fan, a light, a heater, a saw, a drill, a soldeirng iron, .......
you might be able to bring them under the control of one Arduino.
as was noted the DS18B20 is a temperature sensor. it uses one wire to communicate and you can connect dozens on the same wire. it only uses one pin to read them all.
but, if you want to control each thing individually, you might need to use more than one Arduino, or learn about pin expanders (aka shift registers and port expanders and multiplexers ) . chips that can be used to bring in (or out) 4 signals (or 8 or 16......) that use only a few pins to read all those things.
but, there comes a practical time when you want separate things.
as a note, the more things it reads and controls, the slower it does things. it might only be able to read a few dozen things a second, so if you add too many, it might take 2 seconds....
Five DS18B20 temp sensors (one pin), five I2C LCDs (two pins), and five relay modules (five pins) shouldn't be a problem.
Wire length between the LCDs probably is.
So why the five LCDs, and what distance between them.
Leo..
Also, do you need to see the status of one temperature sensor unit from another? If not, then I would go smaller on the Arduino, and drop to a Mini or Micro.
I'm so grateful for all the responses - I knew my question would be short of detail but I didn't want to bore you all with too much detail before I could get across my goal. Knowing that there lies some possibility of achieving this is exciting and I'd like to elaborate further.
My wife and I run a Mobile Kitchen selling Hot Dogs, Burger, Sandwiches, fries, etc and what started out small seems to be growing quick too. At the moment, we mostly have electrical appliances and are limited to one location because the Landlord allows us to use their electricity. We now have requests to setup in different locations and not all of them have electricity so this necessitate gas and we found that gas isn't the easiest thing to control. For us, temperature control is the key to consistent results and would be no different with the gas appliances.
We looking at installing 4 x "5 Liter" Fryers and 2 X "4 Burner" Flat Top Grillers - That's 6 appliances in total - each appliance would need individual temperature control and the LCD would need to display the current temperature at the least.
To automate the process of Gas Flow, I am thinking of using a solenoid valve which will open and close once energized based on the temperature I set.
All this is still on a high level - I'll need to flowchart it but I wanted to know if the Arduino is the way to go.
Gas is way more dangerous then electricity if you have any leaks at all
You can get temperature regulation of a gas burner
A contact thermistor must touch the pan and automatically controls the gas flow.
You can find that technology on many gas ranges.
You can also get an arduino to use a non-contact temperature sensors and put them in the range hood and have them look down on the pan and tell you the temperature of what's on the surface that they see
I should have mentioned that I am based all the way in South Africa and finding a regulator has proved almost impossible without importing it at an exorbitant cost.
Indeed Gas is dangerous however once I have designed a solution, I will enlist the help of a certified gas installer to do the actual work in order to make sure everything is done to best safety standards.
A non-contact sensor will work best on the grillers to measure the work surface temp - as for the fryers, a Probe directly into the oil will work fine.