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Topic: Project - Arduino to know the difference between 2 objects (Read 889 times) previous topic - next topic



I need help deciding which sensor would do the job. The problem is I am doing a project with a Arduino Uno what is 'acting' like a desktop pet where I have 2 LEDs which notify the user that if one goes off it wants some food and the other if it wants a drink. I have made 2 small physical objects that will act as the food and water. And when you press them against the device the LEDs will go off.

Is there a sensor or something that will know the difference between each object? I was thinking of using a RFID reader and placing the tags into the 2 objects. Will this work, and/or is there another way I can do this?

Sorry if it sounds confusing.



RFID is my first thought too. you can also place magnets in the pets with different orientation, but that might be not discriminating enough for a hall sensor.

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


If I was looking to do this in volume I would try to find a material that was opaque in the visible yet transparent in the IR and another material that was opaque in the IR and transparent in the visible and arrange matching photodiodes/transistors.  When the objects were brought in they would block the photodiode from its inband light and you could read the values on the PD's to determine what was in front of it.

I say in volume as it may be expensive to set up a run initially for the "water" and "food" objects.


What about placing a different colour label on bottom of food & water things and using a colour detector.


Nov 09, 2012, 07:13 pm Last Edit: Nov 09, 2012, 07:16 pm by oric_dan(333) Reason: 1
What about placing a different colour label on bottom of food & water things and using a colour detector.

Along these lines,


For a somewhat cheaper form of this, you might try using a blue Led and a red Led, and a simple CdS photoresistor for
pickup. First flash one Led, then flash the other Led.

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