Looking for metal sensor

Other Hardware Sensors
9

krishnapatil:
In my recent project I used inductive proximity sensors . They work really great. They detect all metals in the proximity range. I used 4mm sensors. They are very accurate and available at Rs. 250 in India ( £ 3) which is not expensive.

http://www.nskelectronics.in/inductive_proximity.html

I used 12V, PNP, 3 wire sensor . Connections are as follows

Brown - 12V
Blue- Ground
Green- Signal

Place a suitable resistor between Ground and signal . Due to current flowing in resistor, voltage develops. I tried different resistors but voltage is always around 12V. To interface it to arduino use a 7805 regulator.

Hope this helps ..

Yeah, I was looking at this sensor also earlier. But it looks big for my system since I am building a small robot that can detect metal for this project.
What if I change my objective instead of looking for metal I want to look for a magnet. I did some research and found some smaller sensors such as digital magnetic sensor (http://www.dfrobot.com/index.php?route=product/product&product_id=233#.U0IzB_ldWyU) and hall effect sensor (Shop by Category | eBay). Can anyone tell me the difference between the two? Which one is better or is there any other sensor that better for my project?

Thanks