Need Advice: Stair LED Lights

I'm really new to Arduino and I decided to give it a try. I'm trying to make a stair lights similar to this http://www.youtube.com/watch?v=Ir_cqS6oV5U

My plan is to pick up an Arduino Mega and I am planning to use a 10mm LED lights (from ebay) per each step and an IR LED as a trip sensor. Aside from resistors, wires and a 12V adapter what else do I need? Can anyone give me a tip as well? Like do's and don'ts

Thanks

Stopping in the middle is a problem but I will probably ignore that. It is basically just a guide for me since there are lights on top and bottom. It will be used in the stairs going down to the basement so I don't think I need an ambient sensor.

There will be an IR trip sensor on top and at the bottom. If I trip it on top the light will light up one at a time from top going down and will turn off in the same manner. And the reverse will be if I trip it at the bottom.

I chose the mega since I have 14 steps so it should work as is.

Do you think that's feasible? Can I combine 2 LED on 1 PWM? Can it drive 14 or 28 LEDS (I'm still looking around at the LED but something like this from ebay http://cgi.ebay.ca/20-White-10mm-LED-Lamp-Light-Bulb-Pre-Wired-12V-22cm-/160532881390?pt=LH_DefaultDomain_0&hash=item2560815fee?

I am just starting to plan it right now so everything is flexible and any advice would be greatly appreciated.

Thanks

From the last bit in that video I would suggest he is using two sensors, one on top and one on the bottom, and what I am thinking is that he is using the sensors to run a timed light sequence where the LED's light up sequentially as shown (either from the top or bottom depending on which sensor is tripped). The sequence runs for about 12 seconds from first LED fade-on to last LED fade-off. I think he did a small time study to determine what will be the slowest time that a person (being him) will walk up the stairs (or down), and merely used that as a time guide.

Then programmed the light array to fade-on each LED in sequence, pause roughly 3 seconds, and start fade-off the LED's from the first LED that was switched on.

Hope that makes sense...first time I ever put my hand into explaining a electronic sequence :drooling_face:

P.S. I will describe the sketch in words since I haven't ordered my gear yet.

Wait for sensor 1 & 2 if Sensor 1 = HIGH then sequence 1 if sensor 2 = HIGH then sequence 2

Sequence 1 & 2 is the same, the only difference is the order in which the LED's light up.

Sequence 1 Fade on LED 1 Fade on LED 2 ...... Fade on LED 12 PAUSE 3000ms Fade off LED 1 Fade off LED 2 ...... Fade off LED 12

Sequence 2 will just be the reverse of sequence one.

That what I would do anyway to have the same thing practically and cheaply.

Wouldn't it be better to use the other sensor as the trigger for fading the LEDs instead of using a delay? That way the lights won't turn of in the middle of the stairs...

And another problem is what happens if more than one person uses the stairs... if someone goes up and another person goes down the light would turn off.

Which could be avoided by using 2 sensors upstairs and downstairs which register which way the stairs are used.

And what happens if you step over the sensor? If an alarm would be implemented it would go off for no reason...

Check out this:

http://www.555-timer-circuits.com/motor-pwm.html

The solid state pot could be swapped for a digital one:

http://www.aaroncake.net/circuits/volume.asp

PWM that can be controlled from 3 digital pins.

I'm loving the idea here!

And another problem is what happens if more than one person uses the stairs... if someone goes up and another person goes down the light would turn off.

Which could be avoided by using 2 sensors upstairs and downstairs which register which way the stairs are used.

And what happens if you step over the sensor? If an alarm would be implemented it would go off for no reason...

Hmm, I was thinking that the sensor wants to be half way up the wall really, then you can't simply step over it. Nothing is foolproof unless you have a sensor on each step - then if someone starts going up, changes their mind and goes back down again you know this is the case. Perhaps light up 3 or 4 steps above and 3 or 4 below the step you are on, then sense each step.

Using an arduino mega, there are plenty of inputs and outputs and sensors are cheap enough. I was also thinking of IR reflectance rather than IR gate as if you want LEDs only on one side (like in the video) it will keep the other side clear of sensors and make wiring easier.

If you can get under the steps and they have something relatively thin on them (wood topped for example) then you could have a simple capacitance sensor under each step (possibly wouldn't work if you had shoes or slippers on though)

Just thought about this. The fade out sequence only starts when the second sensor is tripped. In other words, you trip the first sensor and the light fade-on sequence starts corresponding to the sensor. Now the program waits for the second sensor to be tripped before the sequence fade-off. Ok, it still leaves the problem of two people, however one could possibly counter that by using two sensors at each end which will pick-up movement, and hence a second person. Hope that makes sense...