We use magnets
in our everyday life, they hold notes onto the fridge, pick up metal parts that dropped in awkward places, they are even used in some high security keys. We have also seen two different types of magnets, permanent magnets such as your fridge magnet which is always magnetized. And electromagnets
used in applications like junk yard car cranes which can be turned on and off as needed.
One interesting application of the electromagnet is creating a magnetic levitation
device. This is where a magnet is used to lift an object towards it but does not let the object touch the magnet. There are a few ways to do this but here are the operational steps for one of the simpler methods.
- Power is applied to the electromagnet, a metal object will now be attracted to the magnet and want to move towards it.
- A sensor is then used to detect when the object that is now moving towards the magnet is too close.
- The step 2 sensor now causes the magnet to turn off.
- Since the magnet is now off the item falls away from the magnet.
- The sensor now detects that the object has fallen away slightly and applies power to the electromagnet again (step 1)
The sensor is generally an IR sensor which consists of an infrared LED and an infrared transistor. The LED sends out IR light and the transistor looks for the presence of the light. These sensors would be setup so that they look at each other creating a beam, this beam would be located directly below the electromagnet. Any object that gets too close to the electromagnet would then block the beam of infrared light.
Magnetic Levitation devices are available for purchase
, but there is no fun just buying something when you could make it yourself! The video above demonstrated a device built by JHLI
. He doesn't go into the details of building one but have a look at this site
that describes all the steps needed to build your very own.