# Forum Home Renovation Electrical  two way switching with master control

## TwinTrade

i'm in need of all the brainy sparkies out there 
i have a job in a set of offices where they want a master or control switch at the front door so when they leave they can turn all lights off. 
but they also want to be able to walk into one office and turn that light on independently of the master switch. in other words whether or not the front reception master switch is on or off you can turn one office light on and then walk out the front door and turn the same light (and any others) off. 
been racking my brains but haven'y yet sussed out how to accomplish this 
all help would be appreciated 
i'm sure there is an answer
thanks guys

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## Uncle Bob

A double throw switch with one contact being supplied via a contactor (that switches all the lights off) and the other contact being a permanent live.

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## chrisp

Off the top of my head, I can think of two methods.   Wire the individual office lights through individual latching relays.  The on switch would be a momentary on switch (NO); the off would be a momentary break (NC) to make the latching relay drop out.  The "master" would be another momentary break (NC) switch that interrupts the supply to all lights (say, in the wire from the switchboard) making all the individual latching relays drop out.Alternatively, use a PLC.
I've left the details on how to wire a latching relay out as I've assumed you will already know how to wire a relay to latch.  If not, let me know and I'll post details.

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## Batpig

Dear TwinTrade, 
If there is a God, and there is indeed any justice at all left in the world, Nev will pop up here right now and bluntly say:   
"Your Electrician will know..."     :Rofl:  :Rotfl:   
(Sorry - got carried away a bit there... You've got to see the funny side...) 
Best Wishes,
Batpig.

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## TwinTrade

> Off the top of my head, I can think of two methods.   Wire the individual office lights through individual latching relays.  The on switch would be a momentary on switch (NO); the off would be a momentary break (NC) to make the latching relay drop out.  The "master" would be another momentary break (NC) switch that interrupts the supply to all lights (say, in the wire from the switchboard) making all the individual latching relays drop out.Alternatively, use a PLC.
> I've left the details on how to wire a latching relay out as I've assumed you will already know how to wire a relay to latch.  If not, let me know and I'll post details.

  could you expand this a bit please chrisp

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## doug1

Aother way to do this is with a cbus type system if the money is available to support this 
Doug

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## TwinTrade

> Aother way to do this is with a cbus type system if the money is available to support this 
> Doug

  unfortunately the customer doesn't want to go to that expense 
but i still can't see how it will work, it's not like two waying stuff, if the master is "OFF" nothing is going to turn on

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## Uncle Bob

> it's not like two waying stuff, if the master is "OFF" nothing is going to turn on

  Of course it will, follow the dots lol.
And if you wanted to look real smart, wire in a PIR and daylight sensor  :Wink:

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## chrisp

> could you expand this a bit please chrisp

  
TT, 
I've attached a very rough sketched circuit diagram. 
Let me know if you would like more info. 
Chris

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## nev25

> Of course it will, follow the dots lol.
> And if you wanted to look real smart, wire in a PIR and daylight sensor

  Nice Diagram
What Software did you use??  
Dont think it will work as described 
In the diagram the 2 way switch in that position
The contactor switch has no control?

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## Uncle Bob

Thanks Nev, I used paint  :Smilie: 
In the schematic, the contactor is switched off, and the light is in manual on mode.
Edit: As a side note, when I worked for GEC, we had a setup similar to this.

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## Frankmc

Chrisp,s suggestion looks good providing you only have one office lighting circuit....If more than one lighting circuit then use the master off push mech to operate a contactor to momentarily drop off the office latching relays.... 
HTH
Frank

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## bricks

In our office, we have numerous circuits running all manner of things the same as every other office in town I believe.
Our lighting circuit runs through a master switch at the back door similar to what you describe. 
When we are finished for the day, and everyone has left, flicking the master switch will turn off all lights and turn on the "night lights" as we call them.
Once the master has been flicked, no lights will turn on or off but there is a small amount of light should some one still be in the building and need to get out.
Perhaps this is what you might need to do. Just have a master control and some "night lights".

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## watson

*Quick Admin Note:* 
Seems to be some misconception about the use of the forums.
The Renovate forum is for *all*.......like minded Tradies and DIY Renovators.
If there were no DIY Renovators......there would be a lot less jobs for tradies.
There'll be no change to this intention. 
Noel Watson *Administrator*

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## nev25

> *Quick Admin Note:* 
> Seems to be some misconception about the use of the forums.
> The Renovate forum is for *all*.......like minded Tradies and DIY Renovators.
> If there were no DIY Renovators......there would be a lot less jobs for tradies.
> There'll be no change to this intention. 
> Noel Watson *Administrator*

  Dont know where you are coming from 
Obviously missed something 
The original question
Both Diagrams are good answers but doesnt he want to be able to turn individual office lights on no matter what position the master switch is on and then still be able to turn the master switch to turn it off again  
IMO the easiest solution to be Software driven (PLC or Cbus etc)

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## watson

> Dont know where you are coming from 
> Obviously missed something

  No sweat Nev....it referred to a cupla posts earlier on.

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## Uncle Bob

> The original question
> Both Diagrams are good answers but doesnt he want to be able to turn individual office lights on no matter what position the master switch is on and then still be able to turn the master switch to turn it off again

  Hi Nev, the OP doesn't ask about being able to turn the office lights off again after being manually overridden by the contactor, well not that I read, maybe I missed than part  :Smilie: 
Edit: Actually this could easliy be done by changing the contactor switch to triple throw as well.
Switch positions would be:
1: Completely off ( no conductivity at all)
2) Off  with manual override
3) All on
Let me know if you want me to draw it in  :Wink:   
Anyhow, I've changed the diagram to shown how extra offices could be easily added in.
Also note that the DT swiches could/should be changed to triple throw to allow the lights to be turned off completely even if the contactor is switched in.

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## nev25

I may have Misinterpreted this   

> but they also want to be able to walk into one office and turn that light on independently of the master switch. in other words whether or not the front reception master switch is on or off you can turn one office light on and then walk out the front door and turn the same light (and any others) off.

  Uncle Bob
In your Diagram I dont understand the use of the Contactor 
Why not a simple switch

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## Uncle Bob

A contactor will handle loads better, but sure a switch will work if it's rated correctly.

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## Frankmc

Nev 
The master switch would have to be a press/push mech which just break the circuit momentarily to drop off the office latching circuits (chrisp,s diagram)....His circuit still allows the individual offices to turn on/off their lights......If there were lots of offices then a plc / cbus  might be a better option ... 
Frank

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## chrisp

> Nev 
> The master switch would have to be a press/push mech which just break the circuit momentarily to drop off the office latching circuits (chrisp,s diagram)....His circuit still allows the individual offices to turn on/off their lights......If there were lots of offices then a plc / cbus  might be a better option ... 
> Frank

  Exactly.  My "Master Off" is really just a reset switch that places all the other lights in to the "off" position.  Once the "master off" button is released, the individual offices have full control over whether the lights are off or on. 
The one thing I don't like with my design is that it depends upon momentary action switches rather than toggle switches which are likely to have already been installed. 
A possible way around it is to use a PLC or a "smart relay" (a cut down PLC), and use the (existing?) toggle swiches.  The PLC, or smart relay, could be programmed to turn all lights off when the master is activated, but then require the office switches to be turned off (if not already off) and then on to override the master off. 
BTW, for those who aren't familar with PLCs, they can usually be programmed in "ladder logic" which is a relay like programming language.  The circuit diagram I drew can easily be converted to ladder logic and programmed in to a PLC.

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## dambat

PLCs can be very low cost also.  I've used the automationdirect PLCs, which start at around $150, including digital relay driven I/O (12 points?), software, and a 24VDC power supply.  For higher speced jobs, the Allen Bradley PLCs are nicest IMO.
/Damien

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## elkangorito

If anybody's still interested, here's what I've come up with. I did it using "Draw" on OpenofficeOrg 3.

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## elkangorito

I hope this makes things easier to understand.   *Operation description of the above circuit during normal working hours.*
First person to come to work enters the building via the main entrance & presses PB-M1 Start (located at main entrance). This allows all office lighting to be operated normally via their respective switches.
When the last person leaves the office at the end of the day, they press PB-M2 Stop (located next to PB-M1 Start), which will switch off all office lights.
Note that by pressing PB-R1 Start during normal office hours has no affect whatsoever.  *Operation description of the above circuit after hours.*
According to the OP, only one office will be needed "out of hours". I will call this office the "special" office.
Person comes to office & presses PB-R1 Start. This PB can be located either at the main entrance or in the "special" office.
By pressing PB-R1 Start, the "special" office lights are immediately switched on, regardless of the position of the light switch.
When the person leaves the "special" office, the "special" office light can be switched off by pressing PB-M2 Stop, which is located at the main entrance.  *Electrical operation.*
When PB-M1 Start is closed, coil K1 is energised. All K1 main contacts then close, which connect power to all office lighting circuits. K1-3 is an example of this.
Opening PB-M2 Stop will de-energise K1 & therefore open all K1 main contacts.
When PB-R1 Start is closed, coil K2 is energised. All K2 main contacts then close, which connects power only to the "special" office lights. Switch SW-R1 is functionless whilst K2 is energised.
Please note that while K1 is energised, K2 cannot be energised as it is diabled via contacts K1-2. 
K1-1 & K1-2 are auxillary contacts.
K2-2 & K1-3 are main contacts.  *Notes.* 
Note 1  Master Pushbuttons, located at the office front door.
Note 2  Remote Pushbutton, can be located in the special office or at the office front door.  *Legend.* 
K1  Master contactor. Controls all the lighting circuits. Recommended to be rated for AC-3 loads at the required current rating, for maximum life. Control coils are 230 volts A.C. 
K2 - As for K1. 
SW-R1 Light switch in special office. 
T1-11 Terminal connections. 
Lights-R1 Lights in special office.  *Other notes.*
Control circuit to be protected by a maximum 10 amp HRC fuse rated to BS88. Control circuit wiring to be no smaller than 1.5mm2. Circuit is drawn in the de-energised state.

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## rrobor

Ok my two cents worth dont fit a light senser. My mate had a brainwave as to a security device to open and close curtains when the house was empty. A DC motor would open and close them on a pulley arangement and the lot was set up and worked a dream. It only had one flaw, his house faced a road and every time a car came over the hill at night his house flashed it. Proving Burns correct as to the best laid schemes.

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