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need help in selection of sensors

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Muneeb

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Hi
i have to do a project home automation using microcontroller
it will control 3 home appliances a 500w bulb, electric fan, refrigrator
i want the device to respond back whether it is working or not
please tell me about sensors type for this purpose and the name by which
they are available in the market
thanks
 

DavidP

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For the bulb you can use a simple LDR. For the fan and the refrigerator use a temperature to voltage IC like LM35 or AD59X(Analog Devices).

David
 

rafix

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I suggest LM35 from National that have an output 10mV each degrease.

roby
 

lppx

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what about trying with Power Line Communication? this is the actual way to make in-home devices comunicate without adding new wires
 

Marv

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Temperature IC wont actually tell you if the fan is working. Fans dont cool things, they just stir the air, they usually cool people becuase they aid evaporation. If you want to know the fan is on you either need to tell if its spinning, or if theres a strong air flow. Magnetic sensors will tell if its spinning, and how quickly. A hot wire anemometer is a good and cheap way of telling if air is flowing, a constant current source pushes a large current through a fine wire, enough to make it very hot and a voltage reading is taken over it. Put it in an air flow and the moving air cools the wire, reducing its resistance and decreasing the voltage over it. Only real problem is if the device has to last a long time, what to make the filement out of.
 

henrik2000

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Just my 1 cent idea.. A simple IR link (LED and Sensor) placed on each side of the fan, will tell his micro controller if the fan is turning or not.. Hyper simple solution, but I like the 'kiss' concept ! Beside if the IR receiver is connected to one of his micro processor inputs, he could even calculate the RPM of the fan!
:wink:
Marv said:
Temperature IC wont actually tell you if the fan is working. Fans dont cool things, they just stir the air, they usually cool people becuase they aid evaporation. If you want to know the fan is on you either need to tell if its spinning, or if theres a strong air flow. Magnetic sensors will tell if its spinning, and how quickly. A hot wire anemometer is a good and cheap way of telling if air is flowing, a constant current source pushes a large current through a fine wire, enough to make it very hot and a voltage reading is taken over it. Put it in an air flow and the moving air cools the wire, reducing its resistance and decreasing the voltage over it. Only real problem is if the device has to last a long time, what to make the filement out of.
 

henrik2000

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As he is using a micro controller, he is in the digital world.. Why not using a LTC1923 ? Direct digital output on SPI standard interface?
:wink:
rafix said:
I suggest LM35 from National that have an output 10mV each degrease.

roby
 

henrik2000

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As he is using a micro controller, he is in the digital world.. Why not using a LTC1923 ? Direct digital output on SPI standard interface?
:wink:
rafix said:
I suggest LM35 from National that have an output 10mV each degrease.

roby
 

Humber555

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Hi Muneeb:

What about using a small intensity transformer?
You will made it with a small toroid (20-25mm/diam)and a few turns of wire to sense the actual current of the appliance you want to sense. I made it once and the transformers turn ratio is about 1:20, just one turn for the primary and in the secondary of course you will need a rectifier and a signal conditioner prior to the microcontroller.

Best wishes

humber555
 

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