Allotment project....

Hi guys,

i am sure there have been similar posts before, i just wondered as i am new to Arduino if it is up to the task or if i will need multiple units to set up what i have in mind.

I have an allotment with multiple beds. I want to set up sensors in each bed to measure soil moisture (2 per bed to take an average reading) and for each bed to activate the water if neccesary (based on a value, but can be different in each bed - as some plants need less water.)

So something like, Bed1moist = (moisture1 + moisture2) / 2. If Bed1moist <50 start water1 …

I also want to have a central photoelectric, and air temp sensor to monitor the days values, and i know i might be complicating things, hook this up to a servo to open the chicken coop dawn and close it at dusk.

I think overall i might have around 10 beds, so i just wondered if this would be best achieved with an arduino per bed, or would i be able to hook it all up to one?? It would also be nice if i could get the data to output and possibly if needs be have a remote manual override?

Any help, or advice or signposting would be great.

Thanks in advance


so i just wondered if this would be best achieved with an arduino per bed

It could be. Whether that would be best is up to you.

What can not be achieved is trying to use 1 Arduino with 20 analog sensors. So, if the Arduinos are to share information, you'll need some way for them to communicate. In that case, having 10 Arduinos is no more complex than having 3 or 5.

How many sensors would a typical arduino/ardiuno mega support?

I am quite happy to have separate stations that monitor the conditions in each bed. wou;d it be best tp have one for many beds and a separate arduino in charge of watering they they communicate to, and if so, how would they communicate?

I am so sorry for being a pain,. this is all new to me and I am planning everything out now so i know what i need.

Heres a quick sketch based on this thought....

I don't see a need for communication amongst the controllers, for watering only. Every controller can handle one or more beds, and water them independently from other beds.

Communication becomes important for a control center, showing e.g. the humidity of every single bed. Then a master controller, with attached display and more, will connect to all the watering slave Ardunios. Data can be transmitted e.g. by I2C, with every slave controller having a unique address. That address can be hard coded, or better read from an encoder switch, or from EEPROM in setup(). A special configuration function can be used to write that address to the EEPROM once.

In a final system each controller board can have two connectors, with power and communication lines, so that any number of slaves can be daisy-chained. Twisted pair cables are preferable for the communication lines, to reduce interference with the power lines. The power lines should be thick enough, so that even the most distant controller will get enough power for activating the watering valve.

In a more sophisticated system the watering can be controlled by the master controller, so that only one slave can turn on the power consuming valve at a time.

Also take care to check the sensors from time to time. Resistive sensors tend to fail after some time, due to electrolysis, and must be replaced. Capacitive (non-conductive) humidity sensors have a much longer lifetime, and don't degrade over time.