Controlling an AC switch with video?

Hey y'all,

I'm trying to put together an art project where an event in a video simultaneously triggers an AC switch (110V light). I have no idea where to start, whether this can be done with an Arduino, or if there is another solution.

I'm guessing this might be done with MaxMsp on my laptop, but I don't want to leave my laptop in the show, so would rather use some kind of dedicated unit.

Timecode? MIDI? I'm way out of my league here.

Thanks! Marshall

You mentioned timecode, which indicates to me you know the part in the video where the light should be triggered. If you know that, you could sync a countdown in the arduino with the video start.

Could be as simple as 'pushing two buttons at the same time', but if you're using Max then you could get it to trigger (via serial) the countdown on the arduino (one button now not two! but your laptop is required).

Alternatively, and perhaps for fun is to use (coded sequences of) single frame flashes in the video (or find appropriate triggers in the video itself) to trigger light sensors which in turn trigger the light, or a countdown to the light. This way the arduino/light could be separate from the video system, i.e. no more laptop - assuming there is some other video playback device present.

The arduino to relay 110V switching part is the easiest, and I'm guessing there will be lots of tutorials and circuit diagrams online.

Hi, burntcloth

Since you didn't say what kind of event on the video is the trigger, we'll assume that you have control over what is actually on the video. 1:1's idea of quick flashes is probably the easiest. One other suggestion along the same line is a color sensor, like this one: Hook it up to an Arduino and program to recognize a scene that is drenched in a particular color. Then, as 1:1 has said, the light switching is the easy part.

This is an interesting project. Please do post a video if you get it to work with an Arduino.


We only need binary-sensing in this project so a photo-diode can act as a colour sensor with the appropriate gel in front of it ...

I'm thinking also that if your video starts with black then you can just use the first 'not black' part to trigger the countdown to the light - i.e. no special strobes or signals. Ignore everything after that...

With some projection devices you are able to stick a finger right in front of the lens and see no (hard) cast silhouette, just a reduction in illuminance (and a warmer finger), you could try sticking the photo-diode there so as not to fuss up your screen - and then with more or less gel (neutral density 'ND') you can adjust the threshold so the natural room lighting conditions don't interfere.

Another way to keep the sensor off the screen is by sensing reflections from the screen - i.e. the sensor goes (almost) anywhere you like. More chance of false readings this way, the trick in this case is to find a sequence of illumination values over time that are very unlikely to happen at any other time and have the the arduino 'decode' them.

Prob making it sound more complex than it needs to be ;)