Passive Infrared Sensor PIR - You can play with your own at home!

[joebro391]

isn't there a much simpler was to may a non-light-dependent, motion-detector using a PIR sensor? I only ask because i'm very interested in making an interactive table and LDR's won't work because when the light in the room goes off, all the lights turn on. sorry if this is vague. Any advice is appreciated. Thanks man. -Joe

[patrickikis]

You can buy an already-made module from parallax, but where is the fun in that? The reason this looks complicated is because there are no SMD components. This is simply a configuration of the test circuit in the data sheet =)

[joebro391]

@patrickikis oh i certainly agree with you on the fun part, but space is just a concern going into this project. For instance, i can make a light-detecting circuit with 5 components, counting resistors and Loads. that would be optimal and I was wondering if there were any similar circuits with the PIR sensor. -Joe

[patrickikis]

Hi. You're not going to get such luck with PIR sensors. The signals have to be amplified properly, and noise has to be well filtered. A comparator, three resistors and an LDR won't help you here =(

[patrickikis]

A parallax PIR sensor will have everything you need all in one, if that will work for you

[joebro391]

@patrickikis darn, the former was about what i was looking for. I suppose the parallax would work if i hooked up each collector lead of the PIR to an input of some micro-controller, such as a atmega328. what's your take on the project?? how do you think they made such a sweet interactive table?? no bells and whistles, no flickering and wavering.  just motion activated LED's. Thanks for all of this, you've been a huge help man. I hope to have a set-up like yours too, one day. -Joe

[patrickikis]

Hi Jow

I have to say, I'm not really sure what an interactive table is to be honest =s. By the way, the output of the Parallax sensor is digital, I do believe =)

[joebro391]

@patrickikis sorry for not clarifying. An interactive table is where there are dozens to hundreds of LED's, all off, and when the table detects motion, the LED's in the area turn on. I had an idea: a 3-component coupling of an LED and IR LED and an IR Receiver. In a light-sensing circuit, the IR light from the IR LED reflects off of one's hand (or mug or plate) and to the IR Receiver, turning on the LED via transistor. -Joe

[patrickikis]

Hi Joe

The problem is, IR receivers don't pick up on direction. You can be anywhere in a room with a remote and it will pick it up. That is, depending on the frequency. PIR sensors aren't great for direction either. I find that they are only good for movement detection, and even then, I find them slightly volatile. if you want to make a voltage table: LEDs showing the voltage, you need a lengthly comparitor circuit. Easy, but space consuming.

[patrickikis]

You might be able to cascade a bunch of LM3914 units together, but I'm not sure. Have to look at the data sheet =)

Pat