Sensor to detect when a light is turned on

[Pete999]

Where's the painkillers love? my head hurts.

 

[aurumdeus]

Huh, some of the replies only appeared after I posted that last message.

Spoon is right in that I want to use the battery as much as possible, and only use the mains as a backup. I'm hoping that I can get peak usage to use maybe 80% of the battery, so there is still a little left over. Power cuts aren't super regular, but a few times a year. If they happen during the day then no problem as lights aren't being used and the panels will be charging the battery. If they happen during the evening then the lights should already be running from the mains.

I had considered changing the lighting circuits to 12V and directly powering LED's that way. The main issue is the size of the wiring, and getting enough current down the not particularly thick wires to light up a very large house. Also if during winter the batteries run empty then I would have to convert the mains supply down to 12V and send that round the circuits. Given that the person I'm doing this for isn't very technical, I think it might be easier to go the AC route. Also if a bulb goes and someone screws in a normal halogen bulb (or there are no LED ones to hand a a guest is about to arrive etc), the system will still operate.

 

[marconi]

Will you be conforming to what the French/EU regulations for safe use of electricity say about an electricity supply derived from two sources of energisation with automatic switching between the two?

Is your proposed scheme safe for all users?

Remember you are responsible and liable for this design and installation.

 

[aurumdeus]

Lucien that's a good point about separation of the circuits. They will be separated within the relay and the supply from the inverter will go through an RCD, but I don't want to risk shocking a worker (even if only a little). I wonder if there is some kind of heavy duty contact breaker that can be controller like a relay. The mains could power that to keep itself connected to the DPDT relay and the rest of the system as long as it's energised, and if there is a power cut then it will separate itself better than just by a relay. I am friendly with a guy who is an electrician here, so I will check with him exactly what is needed in order to keep everything and everyone safe.

Regarding the short power lag while the relay switches sources, the relays I am looking at have roughly 15-20ms switching time so it should be little enough to not be noticed.

 

[aurumdeus]

This is all assuming I don't encounter anything too problematic when I get stuck in, like shared neutrals between lighting and other circuits, sockets wired into lighting circuits, and so on.

At one point while replacing two adjacent sockets I found 4 different colours of wires being used for live, red, black, blue, and green/yellow striped! This was on a house built in the 1970's, so hardly that old either.

 

[Lucien Nunes]

They will be separated within the relay

You must account for such events as transit arcs, inverted phase and contact welds, so you need to know how the regs and design practice inform the choice of relay / contactor. FWIW there can be up to 650V across the contacts.

and the supply from the inverter will go through an RCD

Have you considered the different grounding arrangements in different inverters - C/T vs. IT vs. earthed neutral, whether the DC input is electrically separate from the output, and how these will affect the functioning or not of the downstream RCD? Otherwise the RCD might appear to be offering protection when it actually is not, and will not trip in the event of a line-earth shock; even the possibility of getting a mains voltage shock off the ELV DC side.

 

[marconi]

http://www.electricalsafetyfirst.org.uk/mediafile/100117573/Best-Practice-Guide-2.pdf

Nota bene

 

[Pete999]

http://www.electricalsafetyfirst.org.uk/mediafile/100117573/Best-Practice-Guide-2.pdf

Nota bene

Are they any better than Heinz beans?

 

[aurumdeus]

I was looking at this inverter https://www.amazon.co.uk/Phoenix-In...coding=UTF8&psc=1&refRID=15DVA1318QJJZW1TDMH2

There is an earth connection on the case itself. I can connect this to the main earth line for the property, or if it would be better drive an earth stake into the ground just for this system.

 

[PEG]

I was looking at this inverter https://www.amazon.co.uk/Phoenix-In...coding=UTF8&psc=1&refRID=15DVA1318QJJZW1TDMH2

There is an earth connection on the case itself. I can connect this to the main earth line for the property, or if it would be better drive an earth stake into the ground just for this system.

Hi,a great deal of the yes/no,of this system,will not be decided by theory or function.
It will be decided by the regulations and recognised specification,in force,where the installation is.
This is especially so,as the properties are open to fee paying,members of the public.

Whilst being enthusiastic,regarding such experimenting,you may be hampered by issues such as the letting insurance,not being able to have standard testing carried out,on this installation.

As an aside,i have experienced systems,working fine...until members of the public turn up,and carry out their own "unique" form of testing,which often involves completely ignoring instructions,followed by indiscriminate and clumsy attempts at a remedy

 

[aurumdeus]

That's a good point about the "unique" testing... I'll add something to the arduino program to make sure the inverter stays on for 5 minutes after all the lights are turned off, to get over issues like kids flicking lights on and off. It looks like I'll have to get stuck in to the regulations governing a system like this. Time to exercise my French!

 

[aurumdeus]

In case this is of any use to anyone, I found a pdf giving the wiring specifications for many different countries with circuit layouts, earthing requirements etc. Also the exact specifications that each country has to follow.

The link is here:

http://www.legrand.com/files/fck/File/pdf/Guide-International.pdf

 

[aurumdeus]

Again, in case this thread pops up on someone's google search looking for French wiring regulations.

This is a document I found written in English that tells you how to wire circuits in houses to conform to the French regulation NF C 15-100

MEGA - https://mega.nz/#!IiRHXZCQ!mdef9kT7WUY4pslnsmsqux5FeEJPRqkxM1GD9c8DAYs

This one is in French but is updated as of February 2017

http://docdif.fr.grpleg.com/general/ouidoo/pdf/MM216017_Guide_norme_NFC-15100_Fevrier2017.pdf

 

[aurumdeus]

It looks like replacing the DPDT relay with a 2NC 2NO contactor will give better isolation for the circuits and conform to the electrical regulations. Something like this one:

CT1 4P 20A 2NC 2NO 220V/230V 50/60HZ Din rail Household ac contactor | eBay - http://www.ebay.co.uk/itm/CT1-4P-20A-2NC-2NO-220V-230V-50-60HZ-Din-rail-Household-ac-contactor-/222285477747?hash=item33c13f3773:g:ZtMAAOSw8w1YBbU1

Funnily enough, a similar contactor conforming to the same regulations costs upwards of €100 over here.

 

[marconi]

You might want to take a look at this:

Blow-by-Blow PV System Efficiency: A Case Study for Storage | Do the Math - https://dothemath.ucsd.edu/2012/09/blow-by-blow-pv-system-efficiency/