How to dim AC lights?

I'm trying to hack an old traffic light, making the 3 incandescent AC bulbs independently controllable and, ideally, dimmable. My thought is to either have a series of buttons or a multi position switch to put the lights into different modes.

Modes could be:

  • regular traffic light operation (green for awhile, then momentary yellow, then red for awhile, etc)
  • dimmable sequence (red on then dim to yellow then dim to green, etc)
  • dimmable random
  • all on
  • maybe somewhere down the road make them react to sound

This would all be pretty trivial if it weren't for the dimming part...

I found this discussion:

Which links to this kit:

But at $32 per kit, and the fact that I'd need 3, and the fact that I'd have to assemble each kit, I'm leery...

I also found this discussion:

Which links to this board:

But can't tell if that does what I need it to do.

I should probably add that I'm new to Arduinos but not to programming. I've been wanting to do an Arduino project forever, and this seems to fit the bill nicely.

Thanks gigantically for any help, and I'll keep this thread updated with source code and schematics as/if the project takes shape.

But at $32 per kit, and the fact that I'd need 3, and the fact that I'd have to assemble each kit, I'm leery...

That is quite reasonable, see other choices:-

But can't tell if that does what I need it to do.

It looks only to be a switch, there maybe some way of synchronising a zero crossing detector and delay but I don't like the safety aspects of this board.

Could dimming be implemented in software with an SSR? Some of those have zero crossing detectors to avoid EMF issues, and they're pretty cheap (compared to that dimmer kit, anyway) and easy to use.


Talk to this guy:

If you do get one of his AC shields, be careful! :o

That "AC shield" does look like it has what you need: in particular, it has the zero crossing detector that you need to time the turn-on of the lights for dimming. It also (as people in that other thread noted) has a physical layout that makes fatal shocks a serious possibility, so be EXTREMELY careful with it.

One other thing to check: that board is only good for 1A per circuit. How much current do your traffic light bulbs draw? It's definitely possible that they need more than 1A (yes, they look dimmer than 50W headlights, but remember that they have color filters on them that absorb a lot of light, so they could well be 100W or more).


Would there be a way to dim these guys?

I'm guessing this would be much too slow:

Yeah those LED lights off ebay would probably be a really good idea.

I have a green one and a green arrow from a traffic light. Obviously all of them are going to be different, BUT, mine is actually made up of two peices that fit back to back - one is a big array of LEDs, the other is a 240VAC to 12VDC converter. I just unplugged the LED board from the power supply an soldered on my own 12VDC power supply, and bam I was shining green like you wouldn’t beleive. it is BRIGHT.

12VDC fading is a LOT easier obviously than mains AC.

No guarantees though about anything, those ones might be totally different. But it might be worth firing off a few questions to the seller.

Wow that would be fantastic if those were 12v. In the past I've owned an LED crosswalk sign, and if I remember correctly it was wired for 48v, which is brutal to work with for me.

Does your have any brand markings on it?

And did you have to physically open the sealed light fixture?

Another solution is based on x10, as described here:

Let's just say the opening of the lights was done by someone in a ute at 2am...

The lights are at home, I'll check when I get back. I'm sure there are heaps of manufacturers out there though, probably all using custom proprietary parts.

i know the blinkenlights guys had big issues with dimming ac current. they developed some modules that are all open source, so if you google for blinkenlights, maybe you find some help.