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Posted by Last week I was chatting with Nevyn/Mark in the chatroom and thanked him for sharing his experience with the TLC5940, a 16 channel PWM driver, with the world. Obviously he wanted to know what I was doing with it, so here it is. The idea is to make a sort of dynamic LED lighting for the stairs. Underneath each step will be a part of a LED strip (white), a detector at the bottom and a detector at the top. If somebody approaches the stairs, the steps should be lighted, one by one. I need the TLC5940 because it is 16 steps, and I don't want the LED's to be just on/off, but I want them to fade in/out. I hope this idea is clear. If not, there are quite a number of examples on youtube.
What I have done so far is get the TLC5940 to work, thanks to Nevyn's blog. I did make some changes though. If you modify the PWM duty cycle linearly, the perception of the brighness of the fading light is far from linear. You could use another function to accomplish an apparent linear brightness, but I choose to make a lookup table, with 64 steps. This allows for easy tuning, in case I am not satisfied with the linearity of the brightness. My daughter made a little movie of the result so far, which can be found here:
Next things to do:
- Code cleaning, it currently is a mess (although it works as intended)
- Create the rest of the logic, that handles a multitude of options properly, like what happens when somebody goes downstairs, while another person is already on the way up.
- Connect more LED's to each output
- Get rid of the crystal timing circuit, to reduce the part count. There is a thread on this forum explaining that this is possible, and replace the timing circuit with output from one of the Netduinos PWM pins.
- Select, acquire and implement actual actuators. I still need to decide what is best. Could be movement detectors, proximity detectors, pressure sensors on the steps, I still have to think this through
- Install the whole thing on the actual stairs in our new house
I will be reporting progress here, but thanks to all kind of other stuff that keeps me busy (like work), it all will take a while.
Best regards, Peter
