In our previous post Digital Backdrop using a TV (Part 1)
we explained how we used a light sensor in a circuit with LED strip lights to react to the video on the TV screen at the back of the layout. This helped combat the silhouette effect caused by having such a strong light source behind the scene.
The light sensor acts as a dimmer switch, allowing the lighting above the layout to increase and decrease in brightness alongside the video — with such precision that it can even simulate a lightning storm. And all of this happens without the need for any kind of computer brain, such as a Raspberry Pi or Arduino, making it both inexpensive and simple to implement.
While this setup worked really well, we were also keen to see whether it was possible to change the colour of the light as well as the brightness. This turned out to be a little more expensive than the light-sensor-and-LED-strip combination — at least, it would have been if we hadn’t already had the equipment to hand. Even so, it proved just as simple to implement.
We were using a laptop to play the video for the backscene, connected to the TV via an HDMI cable. The laptop also had a USB-C port that could be used as a video output, just like HDMI. Conveniently, we also had a portable LED monitor that could connect to this port and act as a second screen. Because it was lightweight, it was easy to mount inside the top of the layout using just a single bolt, with only a small hole needed for the cable. (The laptop is powered through the same cable that carries the video signal.)
Once the screen was mounted, we set the laptop to duplicate the video onto this second monitor. The result was a perfectly synchronised light source that subtly changed colour from scene to scene.
We kept the existing LED strip lights in place too. This reduced the visible impact of the second screen’s colour a little, but it meant there was more overall light on the layout.
This wasn’t the end of the story in terms of how we enhanced the more dramatic scenes on Bond Lane, but from this point onwards the development relied on us creating specific video sequences with particular characteristics. That said, we still use the duplicated-screen setup when playing unprepared videos. In particular, when the layout is running at home, we often display live webcam feeds on the backscene — duplicated onto the second screen to enhance the lighting in real time. A two- or four-minute video loop works well at an exhibition, but it can get a little repetitive when you’ve seen it a few hundred times!
In part three, we’ll explain how we made the light from the second LED screen even more vivid, and increased the impact of the colours to really bring each scene to life.
