Controlling 120v Lights

Note: I am extremely new to electronics. Hence, my User-ID.

I have an Arduino Diecimila. I have 12 LED's that are working wonderfully doing the 'Cylon' scanner-eye thing. YAY!

Now, I want to use the Arduino to control 12 120v red light bulbs. How do I interface the Arduino to the 12 bulbs? I was thinking like 5v to 120v relays, but there has to be a more elegant way to do it.

Any ideas, thoughts, comments or face-slaps for a curious rookie?

Thanks for any honest help. ;)

Cool project :)

How about arduino with 5 power transistors and 5 bright red LEDs?

That will be a lot more efficient than using 120VAC light bulbs which only last for about 1000 hours anyways and will burn out if they are switched on and off frequently


Well, maybe I should have explained a bit...

My Father-in-Law is building a new house. It is HUGE. On one side of the house is an open strip of the siding we had just finished applying to the stick-frame. He said, "Hey.. it looks like a Cylon eye!" Of course, me being a geek and all, I IMMEDIATELY had this idea. They're leaving back home for the winter, so I have a couple of months to fix this gig up.

With the Tyvek? weather wrap on the house, this will be a PERFECT gag for him. (My Mother-In-Law will NEVER let him watch BSG when she's in the room).

So, in my mind's eye, he drives up to the soon-to-be-finished house next Spring and it's sitting there 'scanning' him, except it will be LARGE. About 10 foot long and a foot high.

So there's the deal. Whatcha think? :D


It's not an Arduino, or very cheap, but you could throw this at it:

You can program it with BASIC and it just hooks directly to AC power.

Or from the same site, some of these solid state relay modules, you could connect them directly to an Arduino:

I like the idea of those relays. I can get an 8 position relay and a 4 position relay and go to town. Thanks!

(Keep the ideas coming, people. I might learn something here!)


one option might be a bunch of Triacs and since you're not dimming you probably don't need a zero-crossing detector. Triacs are pretty cheap and because we are just talking about resistive light bulbs, again the zero crossing detector is probably not needed.

A nicely isolated and packaged option might be a bunch of cheap SSRs: 3-8vdc solid state relay good to 1A at $3.25 ea:

But will it all be for not if he shows up in full daylight?

Those Triacs might just be the ticket. Nice and cheap and seemingly robust enough to just do the job.

And if Dad shows up in daylight, which he most likely will, I'll have already made a video of it at night. And, if it goes as I'm imagining it, it'll be bright enough to impress even during daylight!


Relays are not good when you're turning something on and off all the time and the same is true for any type of light bulb, except for LEDs which can be switched on and off very frequently and will last 50,000 to 100,000 hours

Why waste, potentially up to 500 watts of power when you can do the same thing with 5 3W LEDs ( 15W total )?


he could install a sensor at the driveway to send and RF signal to the display to turn it on when someone enters the driveway. This would save power and the relays from waste and wear.

Rube Goldberg is alive and well but super bright LEDs are probably the best choice.

So am I to assume from the comments that 5 3W super-bright LED’s per Arduino port would be good enough? It would CERTAINLY be less dangerous and wasteful. :slight_smile:

I’ve looked at the specs for the Arduino, but still learning the language there.

Thanks for all the responses! I’m learning!

Never mind, I reread the first post and you've already got the LED part going. To determine if LEDs will work, look at the lumin output and compare what the LEDs will do to what your 120v bulbs will do. That should give you a ballpark idea if the LED are good enough for what you're thinking about using.

What I originally wrote: you're going to need to code your Arduino to do the Zylon/K.I.T shuffle no matter if you use super bright LEDs or Triacs and 120vac bulbs. So start that and learn what you need Arduino to do so you'll have a better idea of what Arduino can do. And you can use normal LEDs right off the Arduino pins to make sure you have the timing and effect the way you want it.

Off the top of my head, I'm thinking you might need to use PWM to really get the effect looking right. The leading and trailing lights/LEDs are dimmed while the center is full brightness. But a standard chasing light pattern wouldn't be too bad either. Code it up and see if it's what you want.

Well, I was looking for REALLY, REALLY bright (visible from about 100 feet and THROUGH Tyvek? house wrap), ergo, the 120v bulbs..

Search for 3W red LEDs ( Luxeon or Luxeon clones )

You can find them on ebay and various online sellers|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A1|293%3A1|294%3A50

These things are bright :)

You can get them in white, red, red/green/blue and possibly other colors

LEDs are usually visible for about a mile or more


you might end up melting the Tyvek with 120v lights with enough power to shine through the Tyvek.

Maybe you could see what power 120v light it takes to shine through the Tyvek before deciding on what driver design you use? You probably already have 25W, 60W, and 100W bulbs around the house.

One thing about the LEDs is that not only do they put out way less heat, but the wires can be really thin so you might even be able to slip the LEDs through the overlaping seam of the Tyvek so they are exposed to the outside and don't have to shine through the Tyvek at all.

LEDs run a lot cooler than 120VAC bulbs and would not melt anything nearby

High power 3W Luxeon type LEDs do run hot but are still a lot cooler than regular light bulbs

Also Luxeon LEDs are designed to have a heatsink glued to the back of the LED for cooling so the heat is properly dissipated

With heatsinks mounted on the back it shouldn't be a problem at all :)

You could also use lower power red LEDs, a few bright 5mm or larger LEDs may work too

This can do 70 lumens @ 350mA and 130 lumens @ 700mA


Or you could use an LED cluster like this one

It wouldn’t require a heatsink


Very cool LED cluster disk. So, what I'm hearing is no matter what I do, I need a TRIAC or something like it no matter WHAT I do because anything that's very bright/powerful is going to involve an interface of some sort.

Okay, I dump the 120v and go with 12v LED clusters - now what? As I understand it, each port of the Arduino is only good for 5V/50ma at best, right?


Stick with 120V bulbs and SSRs, plug into your existing Arduino and code, you could have had it working by now.

I am using this:


Received the SSR's. Mocked up a plain old light bulb to the Arduino and it works like a champ. Now to wire up the remaining 11 sockets/bulbs and it'll be scanning away.

Thanks to ALL for the help/ideas. I learned a bunch and I'll be spreading the Arduino 'gospel' to all who'll pay attention!

I'll post a link to the Youtube video of the finished product when it gets here...

I'm off to scare the wife. :D