Building compasses and extracting magnets from electronics

[Cambridgeskip]

So my scouts want to do a survival skills camp.

One of things we've got planned is building their own compasses (as well as other natural navigation techniques).

The actual process of building one out of a magnetised needle is not that difficult. No worries there. What I wanted to do though was take it a step further and raid ebay or similar from some old electronics and get the scouts to extract magnets from them on the spot. As would probably be the case in a real survival situation! Ie break open up your phone, ipod etc and extract a magnet. So far so good.

However.... I am a biologist by education (hence no problem with showing them how to read a tree to find north!) not an engineer or similar. I am slightly concerned by breaking these things open and what nasties may or may not lurk among the various components. I'm thinking heavy metals and the like.

So has anyone done this before? And do you know what bits we should avoid going near? Or am I being overly paranoid?

[Eagle94-A1]

I am not an engineer, so I cannot tell you about nasties and what not. BUT, my sons dismantle old electronics all the time. Computers, iphones, HO scale engines, you name it,they probably took one apart. So far, so good.

 

 

[qwazse]

Many buttons, e.g. T.V. Remotes and older calculators, have lodestones in the plastic buttons. They were used to close circuits without worrying about narrow guides that would wear away after repeated use. Those little buggers have pretty weak fields, however, and make for terrible compasses.

[NealOnWheels]

I am an electrical engineer.  I would not worry much about the lead used in solder.  Just don't eat anything.  Most electronics should be safe from a chemical aspect.  A shock hazard perhaps.

You are not going to find much in the way of magnets unless you have something with an actual coil speaker or motor.  A modern day phone probably has a piezoelectric speaker.  No magnetic material in those.  Transformers will have some ferrous material in them that may have a small magnetic field to them.

Most ferrous material (iron) has a weak magnetic field.  I have heard of inserting a needle  through a cork and floating it on water to make a compass.

[MattR]

Mechanical hard drives have fairly strong magnets in them. It's probably more likely that you'd find a car when lost. Pull out the car speaker. A cell phone does have a battery and using that to make a magnet? With the head phone wires? (Hopefully not bluetooth) We're talking McGyver but the scouts might like it. Everyone I know that has a snowmobile knows how to pull the spark plug and start a fire with it. There are magnetic sensors in most cell phones. You just need the app to read them. I know, not much fun.

[Eagle1993]

What about the cell phone vibration motor?  I would expect that to be magnetic, just not sure how much.  

Note... be careful around any Lithium ion battery.  Mechanical damage to that battery could cause a fire.  Even when the cell phone is discharged there is a remaining charge in the battery ... so the potential exists.

[Cambridgeskip]

Thanks for the suggestions chaps, a few things to go and look out for there.

Off line someone suggested, in terms of things thats scouts might be lijely to have about their person, some phone or camera cases with magnetic clasps.

[qwazse]

8 hours ago, Eagle1993 said:

Note... be careful around any Lithium ion battery.  Mechanical damage to that battery could cause a fire.  Even when the cell phone is discharged there is a remaining charge in the battery ... so the potential exists.

True story: last weekend, I had cracked open a new mini flashlight that came with its own AAA battery. I was having a heck of a time closing up the light until I realized the battery was wrapped in plastic. I gently pulled it out with some pliers, peeled off the plastic, and re-installed the battery. No light. I unscrewed it and tried to reseat the battery, which was gradually feeling warmer ... then hotter! (I thought it could be my paranoia, so I had my SM check it.) Sure enough, the somewhere in the process of packing and removing that battery it became what I'd call a "short" stack. I dropped it in a mini-solo cup (a.k.a. hillbilly demitasse cup), scooped some snow in the thing, and set it out side. It melted about half the snow until it decided that I wasn't going along with its mission-impossible antics!