Hi I'm currently building a smart fan that has motion and temperature sensors, and humidifier. My question is how can I safely connect my 220V fan to the Arduino UNO? I already have a relay but don't know how to safely connect it.
@beginrhuetgf53 You posed about your project in the section that specifically says it is not for your project, so I have moved it here.
Please read the getting the best from this forum sticky post at the start of each section.
Given your question I don't think you understand enough about electronics yet to be playing with maims electricity.
I'm honestly not familiar with electricity, that is why I'm asking for help. Our professor asked us to finish this project and it is still not finish till now, because I have no idea how I can connect the 220V fan to the Arduino UNO. I already tested this project on a 12V and it is working.
if the project works controlling a 12V fan what is the point of testing with mains voltages
problems:
- what is the rating of your relay? i.e. is it rated to handle mains voltages?
- is it opto isolated from the Arduino ? a small error and you could destroy the Arduino and any connected equipment, e.g. desktop PC, laptop, etc
as @Grumpy_Mike pointed out it is not wise to mess about with mains voltages unless you know what you doing
it is very easy to make mistakes - a recent project controlling three pumps I tested using 12v garden water pumps - some technicians then decided to test it using the target pumps which were 240V 2.5Kwatt each - connected the system to a 13amp socket and then wondered why the fuse kept blowing!
Control your 220V relay with a 12V relay?
No.
I think you are confusing the rating of the contacts of the relay with rating of the relay activation coils. No one is talking about a relay that is controlled with a 220V signal. If they are then they shouldn't be.
Well, that's a good start, but it would help to know which of the hundreds of thousands of different relays you have.
If you professor is self-confident enough to accept critic you should demonstrate him your project with a simple LED or the 12V relay that is switched on/off and explain:
Building devices that do switching 220V requires a formal graduation. I do not yet have. For safety-reasons here is the project that demonstrates the functionlaity using an LED instead of really switching 220V.
If in addition to that you could lay on the table the regulations that describe what kind of formal graduation is nescessary to build 220V-devices and what tests these devices have to pass and what measuring -values must be achieved so the device is considered "safe to use"
you would show the highest level of professionality to your professor that goes beyond the assigment-description. (maybe this is exactly what your professor is wanting from you)
If you still would like to switch the 220V you could use a wireless RF-remote controlled 220V socket you buy of the shelf. The socket stays untouched to keep the security-certification of the manufacturer. The RF-remote-control gets connected to the microcontroller.
It must be one of these sockets where you plug in a standard 220V-plug, because as a non-professional you are only allowed to use such standard-plugs
Even connecting a wire to a sonoff-device is against security rules if done by an amateur
The 220V-switching device must be of this kind
standard 220V-sockets for standard 220V-plugs
The RF-remote is battery-operated on 3V to 12V and here you would connect
the microcontroller to one of the contacts of the buttons.
Still this requires some knowledge about electronics
depending on the buttons tecnology. If the button is a conductant rubber-plate this kind is hard to use. It should be one with very classical tactile buttons.
best regards Stefan
I would never have asked students to connect equipment to mains - the health and safety people would have had fits!
an LED going OFF/ON gives proof of operation
Indeed, at one stage I was the physics laboratory academic H&S rep.
There are all sorts of odd things students are not allowed to do.
For example I had to ask female students if it were possible that they could be pregnant before they were allowed to enter the radioactive lab.
Students with only sight in one eye were not allowed in the optics lab if they or anyone else in the lab was using a laser.
Thing is, if it went wrong it was your responsibility, not the student's.
when I was a student we had lab sessions where we carried out experiments on mains voltage AC and DC equipment, motors, transformers, etc. The experiments were specified explicitly - connect X to Y, measure Z, change A and B, etc etc. The labs were always supervised by the lecturer and several technicians usually with the help of research students. We were never left to work on mains voltage kit by ourselves.
That sounds a trifle dubious. 
Why is that? Any laser accident would leave a one eyed person totally blind, as they would be using there one good eye to see the optics experiment.
Because any accident would mean a big payout. Not acceptable for a binocular person at all.
Not in the UK it wouldn't.
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