Arduino project using mains voltage (240v)

Projects General Guidance
1

Hi all, I am currently working on a project which will control my central heating. I am using an arduino and a relay to switch 240v. The project will be powered via a transformer from the 240v feed from the boiler. I'm wondering if I should connect the arduino ground up to the earth on the mains feed?

2

#1 - What experience do you have working with AC and high voltage?

#2 - One side of the output side(Arduino Side) of the transformer you are powering the Arduino from should be tied to ground. That will ground the Arduino.

3

kf2qd:
#2 - One side of the output side(Arduino Side) of the transformer you are powering the Arduino from should be tied to ground. That will ground the Arduino.

I do not understand this: IMO the transformer output side will go to a (bridge) rectifier, earliest the minus side of that rectifier might be Arduino GND.
Or do you call the whole DC power supply module "transformer" ?

I think OP's question is whether it's advisable to connect Arduino GND to Protective Earth or rather not.

4

No I wouldn't connect the arduino ground to your power ground. However if you mount the arduino into a metal box, that box should be tied to the power safety ground.

Lefty

5

sorry if I did not make myself clear, I have a habit of doing that :cold_sweat:

basically then I should just connect the mains ground to the metal box that will be flush mounted in the wall (as you would normally in any socket) and terminate it there? I'm using a PCB mounted transformer & rectifier so I will obviously just connect the arduino gnd to the gnd output of the rectifier.

Thanks all

6

dtokez:
sorry if I did not make myself clear, I have a habit of doing that :cold_sweat:

basically then I should just connect the mains ground to the metal box that will be flush mounted in the wall (as you would normally in any socket) and terminate it there? I'm using a PCB mounted transformer & rectifier so I will obviously just connect the arduino gnd to the gnd output of the rectifier.

Thanks all

Yes, that is how I would do it.

Lefty

7

Thanks lefty thats great. One more thing I have just thought of, would you have the ground plane (arduino connected) anywhere near the mains stuff? I was going to add a full board plane but I'm not so sure, although it wouldn't be too much of a problem if it picked up mains noise would it? Or would it effect analogue readings?

Thanks again

8

Anyone?