I'd like to make an illuminated staircase consisting of 14 steps where the steps light up as someone walks up or down. When a step is detected I'd like to switch on a small LED strip for a few seconds.
Today I had the idea to detect steps by measuring the difference in resistance caused by someone stepping down on this piece of aluminium which is installed on every step. Using the analogue input pins of an arduino I think that should be a relatively easy task, but I need to control approx. 14 LED strips and I'm trying to find ways to minimize complexity and the number of wires along the side of the stairs.
One of my questions is therefore: is there a way to build a small, simple and cheap "control mechanism" that could be installed in each step? In other words, is it possible to build something small, cheap and capable of:
Being powered by 12V
Sense resistance in a piece of metal
Switch a LED strip on and off (mosfest transistor?)
Wait for some seconds
Ideally I'd also like to fade each strip in and out, but in an attempt to keep things relatively simple I've more or less disregarded this feature.
The other question is of course, do you have any general advice on this project?
Edit:
This Tutorial explains how program a single 8-pin ATtiny chip. Perhaps I could run 5V(to power the ATtinys) and 12V(to power LED strips) down the side of the staircase, then use 14 ATtiny chips to control 14 LED strips? Does that sound reasonable or just silly?
I have completed this project. I incorporated the TLC5940, used a 38khz IR detector-receiver pair for the bottom step and an PIR sensor for the upper level. I see no reason for the complication of having a sensor on each step. I used a PIR sensor on the upper level because I wanted the lighting function to start before someone actually started walking down the steps. I also used an LDR to allow the program to detect darkness. My only disappointment is that the 'ramp up' time on every step is rather quick to accommodate a family member that often takes only a couple of seconds to traverse the staircase; so the lighting effect is not as cool as I would like it.
scottyjr: Thanks for your reply. So you have one sensor at the top and one at the bottom and you switch the whole set of stairs on and off? Did you also use LED strips for the lighting? Do you have a forum post, project page or some pictures of your setup?
The idea of having a sensor on each step was to be able to light up the stairs as you walk up or down them, something like this:
Also, I felt I was putting so much processing power to waste having an "entire" Arduino Uno simply switch something on and off.
I realize now that I'm contradicting myself in asking for something relatively simple and at the same time considering using 14x ATtinys. In the end I suppose I'm looking for something that's simple enough that I can actually build it and complex enough that I learn something. (+avoid many wires on the side)
In that video, the stairs do not illuminate as you walk up or down them. The lighting sequence is triggered at the bottom step (I believe the detector can be seen just in front of the first step's light) and continues on without further input. My lighting sequence is just as you see in the video except that the lights going to 'off' is not sequential but all the lights fade to off in unison.
I didn't use any lighting strips. I used two 'top hat' warm white (don't like the institution type output of the cool white leds) leds on each step.
You won't be wasting Arduino processing power since you will not be simply switching something on and off. You will be constantly monitoring inputs and controlling outputs. Along with the Arduino, the TLC5940 is the device to use for this project. It's friendly to use, especially considering the available libraries and documentation for it. It seems a bit pricey but considering the time, money, and frustration that might be involved trying to put something together that can do it's job makes it cheap.
Personally, I never consider an Arduino to be used in a permanent project. I think of the Arduino as a prototyping platform; something very convenient to use to 'proof' a project. In the case of my stair lighting project I made my own board with the main components bering an Atmega 328pu and a TLC5940.
I don't have any pictures to show. The documentation I do have for this project are Eagle files and the sketch I used. The only forum post was about making printed circuit boards.
One difficult aspect of this project was not about components or software but about the wiring of the leds and sensors. It took a lot of time and effort to accomplish neat, simple, concealed wiring throughout the staircase.
