Automating power on/off

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Old 10-20-12, 11:43 PM
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Automating power on/off

Hi ,

I am new to this forums , so HI to all . I am a software developer and just started my journey in electronics side . I had this particular idea which I want to do for my project .

IDEA : Problem statement : In my college every room has fans and light which is powered with normal switches. People when leaving the class don't switch off the fans and lights when leaving the classroom

Solution : I wanted to develop a software which will recognize when the classroom is empty and will switch off the lights as soon as no one is there .

It will have three components :

1. Sensor : This will detect that there are no people in the room and send a signal to the system

2. Software system : Which is responsible for taking in INPUT from the sensor do the processing and send either signal ON/OFF command in some form to the electrical main

3. Main Circuit : This circuit should understand the software command and convert it to signal of some form which makes circuit switch off and switch on


MY PROBLEM :

I am not able to figure out two things .

1. What circuit should I use which can understand a software command and convert to signal ?

2. How can this circuit switch off the power?

I will be greatfull , If somebody can guide if not give proper solution
 
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Old 10-20-12, 11:54 PM
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I'm not really sure of the proper solution for you but they make room occupancy sensors now. They can be self contained 110V type like you would put in a standard switch box or the type I use to do what you are trying to do. You buy a combination power supply/switching relay. It comes in one compact package. Mounts onto a standard 4" electrical junction box. This relay connects to wall or ceiling mounted sensors with 3 low voltage wires. You can run several sensors on one relay in the case of a larger area. When they sense movement they close the circuit and then after an adjustable time delay setting and after sensing no more movement - open the circuit. Wattstopper and Lutron are just two of the players in this field. Search occupancy sensors. Hope this helps. Feel free to ask more questions.
 
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Old 10-21-12, 12:01 AM
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I just wanted to make this clear .So the component which controls the power from the software is called RELAY ??
 
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Old 10-21-12, 12:11 AM
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Basically yes. In your case if you were to start from scratch. You would use an opticoupler or optoisolater. It usually comes in an 8 pin IC chip form. It has an LED and a switching semiconductor in it. Your logic would activate the LED with 5 volts and the switching semiconductor would control a relay. The relay is a device that use a small amount of current to control a much larger one.
 
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Old 10-21-12, 12:18 AM
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And this just last question ? how many sensors are there which we can use to detect presence of human form.
 
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Old 10-21-12, 12:31 AM
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If you were to use an off-the-shelf product like the wattstopper I think it's around 5 remote sensors. I left you two links to the types of units I'm discussing.




Ceiling Sensors

Power Packs
 
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Old 10-21-12, 12:53 AM
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Ok thanks a lot for the help . really helped me .
 
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Old 10-21-12, 01:16 AM
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Any time.....feel free to write back in this forum or send me a PM through the board for more help.
 
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