This form has been very useful to me whenever I needed something.
Eventually my interest in Arduino stuff grew tremendously. I am now working on serious home automation using Arduino / Nodemcu , standard 5v relays and using adapters as power source. The plan is to automate each room in the house to be operable over WiFi.
I in this regards I have some specific questions. I am not a electrical engineer but know what I need to. I am basically a programmer so I don't have answered to these questions.
How safe are Arduino projects for mains devices.
What is the life span of a standard 5v relay
What will happen when relay fails. Will it kill the device ? Can it catch fire ?
Can you give me some tips on working with such a project ?
I did make a simple switchboard controller with relays and ir remote and a few more automation stuff like controlling aquarium lights , watering plants and they are running fine so far. Some over 1 year 24/7 working some 6 months.
This is the first time I want to use wifi and go forward. The device will be a master board which controls all lights and fans with urls and remote. Each device will later be managed by a raspberry pi.
Well historically, a lot of optimists in the field of electrical safety are now dead. With an overview of your post, I'd say you're not qualified to deal with mains circuits. There is a significant risk of killing yourself or someone else. You should only do it with approved, self contained switching circuits factory made for the purpose.
It's one of those areas where, if you have to ask, the answer is "no".
Thanks for the quick response. Can you elaborate a little on how "approved, self contained switching circuits factory made for the purpose." Would be different from a Arduino based automation and what can be the risks ?
Usually I get the electrician to install the devices after making them.
What will happen when relay fails. Will it kill the device ? Can it catch fire ?
If a device "fails", we would normally say it is dead, so we could state it has been killed. We would hope it could not catch fire. Again, check the spec.
Well, you mentioned wifi. So, wifi enabled mains switches and light bulbs are now on the market. So you could just eliminate the Arduino and risky wiring and control them directly from the PI.
If you use a relay not designed for the load, the contacts weld closed.
In this state, too high a current could cause overheating, which could cause a fire.
rajdeeprath:
I never work on the mains when creating though. Only when it has to be installed.
Each closure is of plastic and uses a 6A fuse with the live line. I would really appreciate see directions on this.
I saw so many posts that use relays never heard of them catching fire yet . Hmm
Well, dead people don't post.
The issue of your safety while you are working on it, is only a small part of the necessary thinking. This plea actually confirms that you're not sufficiently aware of the nature of the risks, to implement such projects safely.
I'm sorry if it sounds harsh, but the reality is that it is extremely dangerous and it takes a lot of engineering and 100 years of field experience for the existing consumer electronics base to exist without slowly decimating humanity.
rajdeeprath:
Or is it a rule of thumb that Arduino cannot be used for mains projects ?
It should not be used by someone who has no experience with electrical safety methods and standards, or lacks the assembly skill to ensure its mechanical/electrical integrity with regard to connections, insulation and so on.
You should also be aware that using commercial products for switching mains is not a guarantee of safety. You still need to respect their current rating and not overload them. Also, always consider worst case failure modes. If some part of your system malfunctions due to a bug in the code or a hardware problem will it cause a disaster? If so, think about some sort of a backup so that can't happen.
As well as considering the safety of the equipment being used to automate each room you need to consider the safety of the equipment being automated and the overall idiot proof rating of the system. You might for example automate a switch that powers a pump for an aquarium, but can somebody replace the pump with a heater. You may have a non-radiant, electric, oil filled heater, which is pretty safe, but what if somebody has put clothes on while it was off and it turns on automatically. Can children/animals get caught in automated window blinds etc etc.
I am not a fan of home automation, I like to switch things off and unplug them but that is becoming increasingly difficult.
Make sure that those ceiling fans can never be started while there's someone with their head between the blades... an automatic start can be a serious safety issue with those things.
wvmarle:
Make sure that those ceiling fans can never be started while there's someone with their head between the blades... an automatic start can be a serious safety issue with those things.
