Detecting Proximity to Specific Object

I'm trying to create a circuit which will act as a switch. When an object is in close proximity to the circuit, the switch will be closed. When the object is far away the switch will be open. Does anyone know of a simple way to do this kind of thing? I tried searching, but the only thing I find is proximity sensors which find distance to ANY object (such as ultrasonic sensors), not to a specific object. I'm guess what I need is some sort of transmitter/receiver combo. Ideally I would like this to work without an arduino... but I am worthless with electronics, so I hope that one of you guys will be able to lead me in the right direction :slight_smile: Any help is greatly appreciated!

SOmething like - Arduino Playground - HomePage - or - Arduino Playground - CapacitiveSensor - ?

Some details would be necessary, distance? size of object? accuracy? time response?

@robtillaart: Those seem like sensors to see if a person is touching the object, no? Not quite what I need.


Distance: objects must be in close proximity for the switch to close - say 5cm or less (could be much less than that too, but preferably not more)

Size of object: 10cm x 10cm x 10cm cube

Accuracy: I don't actually need to know what the distance is, just if it's within the small range. Could be off by a few cm, not an issue.

Time response: preferably almost instant, but not critical. Can be a second or two.

Basically what I'm trying to do is put something inside of my object that will turn on a circuit in the object when I place the object next to a "dock" of sorts. The circuit should not turn on, however, if it is placed somewhere else. That's why I need something to detect proximity to a specific object, not just any object.

I hope this info will help you guide me in the right direction!

All your requirements just "slip" in RFID designation.
But before you jump up and go to spend ~50$ on device, have a look in this section:
you could find something, like magnetic hall sensor just for 50 cents?

Yeap, like Magician said, a cheap solution would be a Hall effect sensor (aka magnetic fields). Your object would have the magnet inside and the dock would have the sensor. Check proximity range for different types of Hall sensors.

Sorry for taking a while to respond, I've been very busy lately!

I've looked into the Hall Effect sensor and it seems like it will do the job. Thanks so much for the link and for the suggestions!