small home automation system

Hi everyone,

I have a plan to put together small home automation system.

For now I was just playing with smaller parts like single type of sensors at once etc... I would like to ask for opinion & check of my scheme if basic idea is ok, before I plug everything together. I saw many variants of externally powered Relay Board, so I am little confused and I am not sure if its ok.

Basic idea is to see data & control everything from website DHT sensors (read and display data on website graphs) - only DHT22 nr1 will trigger PC-FANs 1 & 2, when temperature or humidity is too high PC-FAN (1 & 2): they run ON all the time (set time from ... to ...) LED strip (1 & 2): they run ON all the time (set time from ... to ...) (LED strip has to be on separate power line since current A is to high for single relay) Soil sensors (1-4) (read and display data on website graphs) Water pump (1-4) each separately triggered for period of time when humidity in soil is to low (from Soil sensor 1-4)

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very interesting home that needs 4 soil sensor and 4 pumps...

as a note, it is common to tie all grounds together.

if you truly are using an opto-isolator, it is possible to not do that,.

with all those relays and pumps on the same 5v power supply, you might want to condition the power at the Arduino.

I would use FETs instead of the relays.

Adding an RTC to the system could help.

Thank you both for answers.

The pumps are low consumption Vc: 500mA at 4.5Vdc Would it help to put separate power source for rasp/arduino (and seperate for pumps and relays)?

I would like to keep thing as simple as possible :) and using FETs would be too much for start, maybe next time if I finish this one. Adding RTC to Raspberry or Arduino?

Sebsons: Thank you both for answers.

The pumps are low consumption Vc: 500mA at 4.5Vdc Would it help to put separate power source for rasp/arduino (and seperate for pumps and relays)?

I would like to keep thing as simple as possible :) and using FETs would be too much for start, maybe next time if I finish this one. Adding RTC to Raspberry or Arduino?

not sure how the RTC would help. you already have it tied to the net and such. ??? with such small pumps, the power supply is fine. if they all run, then 2 amps' relays are ?? 100mA each ? so another amp for them. couple caps and all is good.

I do not know how would help RTC as well, but as you mentioned I get clock from net (local net) and if local net is down, than everything is down...

Relays should take 71,4mA each, according (Coil Voltage Code 5V) specs: https://www.ghielectronics.com/downloads/man/20084141716341001RelayX1.pdf So that is little more that 0.5A .. + 2for pumps = total less than 3A@5V while my PS has 5A@5V.

What did you mean by couple of caps.

If I had to rely on the net for function, that would not be good. The net goes down sometimes, even for 24 hours or more. I would use the net for monitoring and adjustments but have the program be able to function on its own should the network fail.

Nasa: If I had to rely on the net for function, that would not be good. The net goes down sometimes, even for 24 hours or more. I would use the net for monitoring and adjustments but have the program be able to function on its own should the network fail.

In my case I do not see my Rasp / Arduino rallying on internet. I have setup NTP server on one of my local machines which is checking time over internet, but as fallback it has its own RTC.

So only possibility to stay without local network is get out of electricity, so in that case even Arduino & Rasp. will not be able to work.

Or I am missing something else.