Making a stair light up

So my friend has this stair… This is the beginning of my explanation every time I tell people about this project. Well… My friend has this stair which is made of glass blocks that protrude from the wall. is it amazingly cool to look at and quite creepy to look through to the floor when you walk up or down. I’m scared big time when I walk down because the steps can be a little hard to see sometimes.

The steps are anchored in a huge steel plate hidden behind the plaster wall. Each step are made from 5 layers of glass which has I’ve been told has been treated to extract the iron from it, to make the glass look less green and ‘pool’-ish. What is even more cool about the stair (and my friend and his wife) is that when I asked if I should make the stair light up – they said yes!!
First thing that crossed my mind was piezo sensors to detect individual footsteps around the stair, but after a bit of thought I found that it might have to wait for version 2 (or 10!).

So i took the opportunity to play with the WS2801 chip. it’s a cool little device with 3 8-bit PWM outputs controlled by a serial interface. First, of course, a prototype was made. This was primarily to test out if I had it all wrong.
I am using the internal reflection property of the glass to make the light go from a small area to the whole step. Since the step consits of so many layers of glass I’ve decided to only put light in the middle three layers, which is also a bit thicker than the outer ones.

I’ve bought the standard 5m RGB LED strip, with 300LEDs. On each step I put 9 LEDs on each layer, so a total of 27 LEDs on each step. The stair has 14 steps, so a total of 378LEDs are needed. Each step will have a WS2801 controller with a NFET for power control. The connection will be a 4-wire interface, with 12V and ground, data and clock.

Seeedstudio has this PCB service that I really like. I designed some boards and put them on along with some other project. This was the result:

This is just to show that they produce some really nice stuff out there! I just needed to saw out the pieces that I needed and solder them up.

So this is what the controller part looks like. The input is on the right, the output is on the left. The LED strips attach to the pads on the top.

And a fully assembled system for one step. I can tell you that these are really, really bright! Even if I did try to record them on my camera the sensor would bleed through in no time.

 

Luckily my friend is also a photographer, so I can hope for some nice video and photos when it is put up!

Next thing up is the controller for the steps. It will include a mic to listen for music and use the stair as a giant VU-meter or graphic EQ. also, the apple ‘breath’ will be on the list of functions. Stay tuned.