LED stair sensors and other progress

Posted by Erica on Feb 1, 2011 in Electronics, Making |

I’ve received a few comments and e-mails about the LED stairs lately, and I want to thank everyone who took the time to contact me. Although I haven’t posted in a while, I have been moving forward with the project. When it is complete I plan to publish a full list of materials and schematics so others can make their own.

The next step has been to add the sensor that will detect when someone is on the stairs. I decided to go ahead and cannibalize Robie’s PING))) ultrasonic sensor, partly because Robie sadly did not survive the kids playing with him, and I am already familiar with the PING))) library for the Arduino.

There are probably good alternatives for this sensor in terms of price or function (it costs about $30, so two of them is certainly an expense). I have noticed one quirk with the PING))). If there is no object in front of it within a few feet, taking a reading is noticeably slow. It will wait until the sound wave has bounced back. This can mean that a fast moving foot will not trigger the sensor. I have not yet tested if the opposing stair wall is close enough to get around this, but my feeling is that it won’t. I’ve decided to look at this as a feature, not a bug. I don’t always want to trigger the sensor; during the daytime, for example, lighting up the stairs is unnecessary. This way I can simply start the sequence by placing my foot on the bottom or top stair for a moment, and bypass it by default.

I’ve written and tested the code for the upward sweep of lights. At present, this is not too fancy; they turn on one by one, starting with the bottom step and going to the top. There is a pause, then they turn off one by one starting at the bottom. The downward sweep will be the same in reverse. The beautiful thing about using the Arduino is that I can easily reprogram the light sequence if I get bored! I could even make it do random variations.

I’ve gotten the other mundane things I need to install everything. The second sensor, a grounding strip, bell wire, etc. I managed to misplace the thin aluminum sheet for mounting the PING)))s so I need to get to HacDC and scrounge, or go to the hobby store (again).

I have the perfboard ready for permanent soldering. Then the next step is drilling holes in walls. I’ve been a little nervous about this, I won’t lie. But as install jobs go, this should be straightforward. The back of the stairs is immediately above the unfinished part of our basement, so all I’ll need to do is drop the wires down. I have a wall snake but I may not even need it.

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  • Muhammad Naeem says:

    i am doing a project and it is a stair climbing robot ,so for this purpose i want your help.i don’t know the stair sensing sensor .so kindly tell me the suitable sensors for stair sensing.If you have a helping material about this kindly mail me as early as possible.i am very thankful to you.
    Naeem Sarwar

  • Erica says:

    Dear Nareem, the parts list for the stair project is here. Parallax PING is the sensor I used.

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