Once again both incredible films and yes I'm UK based I shall have a look for the components etc. The chip should be easy enough to programme

 

I would suggest you have a look at this thread http://forum.allaboutcircuits.com/threads/red-and-green-leds-to-show-magnetic-n-and-s.96034/#post-712410
I built something very similar to what you are looking for, and it has worked very well.
I got a lot of help with circuit design from other members here. Unfortunately the detection distance is in mm's rater than inches but the sensitivity will depend on what ever type of hall sensor you decide to use.

 

Far too much technicalities for me to fully understand haha

 

What? Its not magic?... Son of a b...
Whats next.. Please don't tell me Santa isn't real..

I do a "similar" trick.. But I look away and have them hold the hand with the coin in it against their forehead for about 20 seconds and tell them to "think" really hard about it..
Then I have them turn around and face me and then hold both hands out in front of them and I can guess which hand the coin is in EVERY time...
Anyone want to guess how that trick is possible?

No one guessing? Well I'll start, even if it's bad.
• Like holding your arms in a doorway, one will be higher than the other
• The clench will be tighter on the hand with the coin in it, or the opposite
• The grip is formed with two fingers to hold a coin and the other hand is faking a full grip
• You may get some decreased blood flow from holding it against the forehead, the hand recovering from being held against their forehead

Blame the early morning and the weekly roundup email from AAC that brought me to this older thread.

 

No one guessing? Well I'll start, even if it's bad.

• You may get some decreased blood flow from holding it against the forehead, the hand recovering from being held against their forehead

Yep.. The hand with the coin is always "whiter/lighter" in color than the one without due to holding it above your heart..

 

Yep.. The hand with the coin is always "whiter/lighter" in color than the one without due to holding it above your heart..

I wasn't exactly right, and I took a shotgun approach to solving it. That was going to bug me, thanks.

Any suggestions on what the most sensitive hall sensor is anyone? Sensing the magnetic field where you can set a threshold instead for switching seems needed. The circuit using a hall sensor is simple: Vcc, ground, and output. I needed a pullup resistor from output to Vcc, low when detecting certain polarity, nothing with the other polarity. Check the sensor you choose.

I'd start there, see what kind of magnetic field distance detection you can get from a magnetized coin. I've just used a hall sensor as designed for a tachometer. I'd want two sensors if you can only detect one polarity each sensor, where one would be heads and the other tails, so you would know if you were getting readings either way.

 

Is there no way to programme a chip so not only does it sense the magnet but also senses the polarity? This meaning I don't need two sensors?

 

Is there no way to programme a chip so not only does it sense the magnet but also senses the polarity? This meaning I don't need two sensors?

Now that I think of it Magnoemeters are sensitive enough for the earths magnetic field and would easily be thrown off by a magnet nearby and they can do every axis, and they are MEMS (tiny) the problem then being modules are bigger, not design a custom PCB.