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LED motion detector

 
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daves
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Joined: 24 May 2008
Posts: 5

PostPosted: Fri Sep 05, 2008 9:52 pm    Post subject: LED motion detector Reply with quote

I'm thinking of making a device that will cause a LED device to brighten as someone approaches it/walks up to it. 3 leds that would brighten 1/2 per for a total of 6 settings. Would a motion detector or a radar unit do the trick? And if so where could I get the plan/parts....

I've got a glass globe that would grow brighter as you walked up to it..... Could be cool...
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Alan
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Joined: 29 Jan 2006
Posts: 1399
Location: Winnipeg, MB

PostPosted: Sat Sep 06, 2008 8:17 am    Post subject: Reply with quote

You could use an ultrasonic sensor that would be read in with a microcontroller and adjust the LED duty cycle accordingly.

http://www.parallax.com/Store/Sensors/ObjectDetection/tabid/176/ProductID/92/List/1/Default.aspx?SortField=ProductName,ProductName

If ultrasonic isn't to your liking have a look at IR
http://www.acroname.com/robotics/info/articles/sharp/sharp.html

A motion detector would only give you a binary output (someone is there or not). Radar should work but I am not sure if there is a small sensor that is DIY friendly.
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daves
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Joined: 24 May 2008
Posts: 5

PostPosted: Sat Sep 06, 2008 12:48 pm    Post subject: Reply with quote

[quote="Alan"]You could use an ultrasonic sensor that would be read in with a microcontroller and adjust the LED duty cycle accordingly.

Alan,

I wonder if it can differentiate between movement and stationary objects in itís rangeÖ
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Alan
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Location: Winnipeg, MB

PostPosted: Sat Sep 06, 2008 4:49 pm    Post subject: Reply with quote

You could write an algorithm to do that. For example if the value doesn't change for awhile you know the target has stopped moving and then you could turn off the light.
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daves
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Joined: 24 May 2008
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PostPosted: Thu Sep 11, 2008 10:58 pm    Post subject: Reply with quote

Can you recommend a micocontroller to me that will be cost effective... grin..
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daves
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Joined: 24 May 2008
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PostPosted: Sun Dec 28, 2008 8:14 pm    Post subject: Hardware needs Reply with quote

OK, I think I've got the first 2 stages to a 3 stage system, 1. sensor array 2. microcontroller (pic) 3. is the components from the microcontroller to the ledís, Iíve got about 150ís lights per circuit using 2 circuits using a total of about 300 leds (thanks Alan)..

How does the microcontroller tell the ledís to light up or dim? There must be some circuitry between the 2Ö.

Thanks for your help with all of this,

dave
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HyperHacker
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Joined: 19 Apr 2009
Posts: 11
Location: Yes

PostPosted: Sun Apr 19, 2009 6:07 am    Post subject: Reply with quote

I've been thinking about similar ideas for a while, how to get a computer to know whereabouts I am. A couple ideas come to mind. They might be useful in your case depending on the place you intend to set this up.

The simplest idea is to have laser sensors in the doorways. Just a laser pointer shining at a photocell (preferably in a small tube at an angle, so the room lighting won't hit it), with the computer watching its state. When the laser is tripped you know someone's passed through the doorway. With some simple logic you can determine which direction they're going. (The program can assume you're in the room when you start it, so if it sees you trip the sensor, you're most likely leaving.) It gets trickier if you have multiple entrances and/or people though.
This could likely be done without a computer, though I wouldn't know how. Razz
Instead of laser sensors you could use pressure switches (buttons under the floor tiles, etc), sonar, or even just manual pushbuttons if it's just to tell the computer "OK, I'm out of bed and in the kitchen, you can stop the alarm clock now." Laughing

A more complex method would be to use a webcam, maybe with an infrared filter, to actually see where people are. You'd have to write a fair bit of code, and detecting motion in a video stream is not the easiest thing in the world, but if you did it right you'd be able to track any number of just about any living thing in the room. (Maybe not the plants but you can probably assume they're not moving around much anyway. Wink)

Another thing you could do is wear a transmitter on your person, that the receiver reads to see how close you are to it. You could have multiple receivers to triangulate your position. You probably already have a cell phone with Bluetooth; I'm not sure how but some software can tell the distance of the phone from the receiver with only one receiver. I don't know how accurate it is though as I've never used it, but I've heard it's good within a few metres.
The downside to this idea is whoever you want to track has to have a transmitter on them at all times, which needs a working battery. Since you probably don't want to surgically implant any home-grown electronics into you, that introduces the possibility that you forget or lose the thing somewhere, and if you want to put it on a pet then you might have to worry about waterproofing and other such issues. Of course this also won't work if you want to know when strangers are around, or friends who aren't comfortable with wearing a tracking device. Also interference could be an issue with this.

I'm not sure how RFID works but it'd be a possible alternative to the transmitter idea; the tags don't need a power source, so you could just sew one into the inside/pocket of each pair of pants you own or something. Although then you might find yourself constantly setting off alarms at stores. >_>
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