Wiring colour code for 12v and 5v

[unclebob1]

Domestic mains uses blue/brown for normal identification, is there an equivalent for 12v and 5v?
I'm setting up a system of relays to control 230v AC from a 5v dc relay (with a 12v one in between). Thus I have a psu which is outputting 12v dc and 5v dc in close proximity to 230vac. Easiest method for simple verification of what is what is by colour of wire (not to be relied upon but ideally as I'm doing it is rather use conventional standards!).
Is there a standard for colour coding 12v dc and 5v dc?

 

[bernardgreen]

Is there a standard for colour coding 12v dc and 5v dc?

No there isn't.

 

[nickjb]

I don't think there is a British standard but in pc power supplies it's yellow for 12v and red for 5v

 

[davelx]

It's very common for complex ELV control systems to be wired all in a single colour, often white:

http://uk.rs-online.com/web/p/hookup-equipment-wire/7482140/

Then numbered sleeves are used at each end (or not!), which may be referenced on the circuit diagrams:

http://uk.rs-online.com/web/p/cable-markers/0554484/?origin=PSF_412515|cav

 

[Deryck Tintagel]

It's very common for complex ELV control systems to be wired all in a single colour, often white:

http://uk.rs-online.com/web/p/hookup-equipment-wire/7482140/

Then numbered sleeves are used at each end (or not!), which may be referenced on the circuit diagrams:

http://uk.rs-online.com/web/p/cable-markers/0554484/?origin=PSF_412515|cav

I do this myself but with pink wire (a habit from my days in defence electronics).

Just curious as to why two relays with different coil voltages? I presume the 5V relay is on-board and not capable of switching the current required on the mains side? or the circuit board is not capable?

 

[davelx]

I do this myself but with pink wire (a habit from my days in defence electronics).

Ah yes, the pink mil-spec stuff, I remember it well (the first Digital FAX machines made by MDCL for a Game Bird)

 

[bernardgreen]

Using bi-colour wire can mnake life a bit easier for the servicing of equipment with very large cable harnesses.

for example

Pink/black 0 volts (12)
Pink/red 12 volts
Pink/white control / signal wires on the 12 volt system

Violet/black 0 volts (5)
Violet/red 5 volts
Violet/white control / signal wires on the 5 volt system

Wire numbering is a very valuable addition.

Just curious as to why two relays with different coil voltages? I presume the 5V relay is on-board

If the outputs from the logic 5 volt circuits are available as TTL or CMOS logic levels then the ULN2083 octal driver chip will drive upto eight 12 to 24 volt relays. The only down side is that the relays 0 volt and the logic ( 5volt ) 0 volts have to be commoned. One ULN2803 is a lot smaller than even one 5 volt relay and uses none of the 5 volt power supply

 

[bernardgreen]

Purple is king

An entire house was wired in single cores, all purple with wire numbers. And in the garage were several more reels of purple in various sizes.

 

[unclebob1]

Cheers for the response.

The 5v is to power a raspberry pi and relay board - bv4627. it is capable but remains energized while switched on.
the 12v is to switch sclr-2 relays - latching so no need to stay energized.

The sclr-2 then acts as a replacement for thermostat on a heatmiser underfloor controller.

couldnt get the pi to throw the sclr-2 directly due to power requirements so using the bv4627 as a go between.

I've been using a mixture of red/black and brown/blue with various insulation tape to mark what each wire is, but will be getting some marker rings to tidy up. Will then put a piece of each on the cover and mark up what is what voltage so when i come back in a year i don't need to remember!

 

[bernardgreen]

and mark up what is what voltage so when i come back in a year i don't need to remember!

Full documentation is essential. It is amazing how much one forgets in a few months.....

 

[unclebob1]

Full documentation is essential. It is amazing how much one forgets in a few months.....

Most defo - everything is on paper at present, so i can remember one day to the next! (lots of different projects at the moment!)

 

[magicmushroom666]

Using a latching relay as the output from a thermostat might be a bad idea, as if the controller locks up or fails in some way, the heating element could remain switched on until something goes wrong! Keeping a normal relay energised during the heating time would be the normal way something like this would be done, its not like the relay will use much power, especially compared to the heating elements.

 

[unclebob1]

This is being used to turn on/off a gas boiler, if the relay gets stuck on, and the water over heats, the boiler has built in function to shutdown if over heating as a fail safe.

I am also looking to put a second set of relays on an independent pi and on a separate psu (And ups!), if any area gets too hot then alert and disconnect the underfloor controller from the boiler, until i manually reset.

The reason for the latching relay was to allow me to manually turn on a zone or zones in case of failure of hardware/software while i reset and fix, but also allow me to use a lower powered PSU.

 

[Deryck Tintagel]

Using bi-colour wire can mnake life a bit easier for the servicing of equipment with very large cable harnesses.

for example

Pink/black 0 volts (12)
Pink/red 12 volts
Pink/white control / signal wires on the 12 volt system

Violet/black 0 volts (5)
Violet/red 5 volts
Violet/white control / signal wires on the 5 volt system

Wire numbering is a very valuable addition.



If the outputs from the logic 5 volt circuits are available as TTL or CMOS logic levels then the ULN2083 octal driver chip will drive upto eight 12 to 24 volt relays. The only down side is that the relays 0 volt and the logic ( 5volt ) 0 volts have to be commoned. One ULN2803 is a lot smaller than even one 5 volt relay and uses none of the 5 volt power supply

I was wondering about using an octal driver or possibly a FET to drive the main relay.

 

[unclebob1]

It was suggested by a number of people on the raspberrypi forums, however i lack the knowledge to put something together, and instead opted for a ready made solution of sort. There are a lot of issues with feedback from the relays damaging the pi's. the Bv board eliminated these as the board is controlling the switching rather then the pi.

It seems a lot of people are controlling mains 230v using octal drivers or similar, but its just out of my field of knowledge.