AC lighting project, multiple bulbs, one dimmer

Thread Starter

opacey

Joined Jan 19, 2017
3
Hello, I'm hoping for some help designing this circuit.

- UK mains power
- a single wall dimmer switch
- a lamp

The lamp is made of...

- 5 or 6 bulbs, one above the other up a wall
- lower bulbs are orangey warm red like sunset
- higher bulbs are cool white like mid day sun
- as the dimmer is rotated from minimum to maximum first the lower bulb gradually comes on. As it is getting brighter the bulb above begins to come on too, but not as bright as the first bulb. In turn each bulb comes on until maximum when they are all on full. The first bulb should be fully on by the time the dimmer is about half way.

The effect should be something like the rising sun.

I could do something digital with an arduino, PWM modulation and LED bulbs where I have a bit of experience but I'm hoping there's a more robust way this could be achieved with resistors and maybe capacitors, things I know less about.

The wall cabling is done already so I cannot change that. One distribution board in the middle with a twin and earth cable off to the switch one way and another off to the lamp socket the other way.

Any help very greatly appreciated!
 

djsfantasi

Joined Apr 11, 2010
5,682
A clarification as to how the lamps on the wall are wired?

Is there one line and the bulbs are in parallel or does each bulb have its own ground, neutral and hot?
 

MrChips

Joined Oct 2, 2009
19,378
I am going to assume that this will be manually controlled and it is for something such as stage lighting in live theatre.

I offer a mechanical solution.
Use individual AC light dimmers using slide pots.
Have a long bar with a slot down the centre-line. Each slide pot has a post that fits in the slot.
Hence you can adjust all pots at the same time with any ratio between the first and last pot depending on how you angle the bar.
 

Thread Starter

opacey

Joined Jan 19, 2017
3
Thank you all so much for taking an interest in my question!
I particularly like the mechanical solution but it isn't quite what I'm looking for as I want the controller to be remote from the bulbs and I only have one cable between the controller and the lights.

To clarify a few points I missed before...
- I spent months and months building a studio in my garden, its interior is birch ply clad and it is my pride and joy. The only thing not complete is the lighting because I cant figure out the design (and have restricted my self a little with the wiring).
- By the door way is the light switch/dimmer.
- On the far wall is a wall socket controlled by the light switch.
- They are connected only by a twin and earth cable.
- I will build the multi bulb lamp with all the genius electrics you suggest and that will all have to plug into that one socket.

So there you have it. Is there a way to do it so that someone can walk in, turn up the dial, and be greeted by a rising, brightening, warm welcome of a light?

...or is that impossible with just one twin+earth :(
 

djsfantasi

Joined Apr 11, 2010
5,682
I am concerned that, as you described, it would be impossible with one twin cable. Perhaps what I believe is a twin + earth is mistaken. What you need is one conductor per LED. Otherwise as @Bernard noted, the most you could control would be two LEDs or two groups of LEDs.
 

Thread Starter

opacey

Joined Jan 19, 2017
3
Darn!

My naive idea was that I could wire up all the bulbs in parallel, have a small resistor on the lower bulb and then gradually larger and larger resistors on the higher bulbs. The thinking being that the upper bulb would receive less power than then lower ones, until enough juice was coming through that all of them would have enough to reach their max brightness.
No go?
 

Bernard

Joined Aug 7, 2008
5,283
I assume that there is access to the socket wiring ? Is there space for a junction box near the sockets ?
Bulbs might be like auto. LED stop lights, & back up lights ? Low V, say 12 V.
This is not going well as we do not wish to use neutral as power & signal return, instead put a AC to DC power supply at switch location. Now lamps & signal return can share a common line. One line free for programed control signal. Seems to me that as upper bulbs reach full brightness the lower reds should fade away.
Or put control & PS near bulbs, just on-off SW at entrance ?
 
Last edited:

Dodgydave

Joined Jun 22, 2012
8,465
Only way to dim mains bulbs is with a Triac dimmer, or capacitors in series with each bulb, as you only have one twin/earth cable all bulbs will be in parallel across it,....
 

MrChips

Joined Oct 2, 2009
19,378
One dimmer switch, one electrical cable.

Connect your incandescent light bulbs in parallel fed from the wall outlet.
Choose light bulbs of different wattage rating, 6, 12, 25, 40, 60 watts. Experiment with different light bulbs.
 
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