you can visualize the time-changing effect using different methods, the easiest will be using some LED's wich will turn on and off .. but Heyyy .. how cool is that ! .. alternativly you can use a flip-dots. you can buy these at :http://www.flipdots.com/EN/electromagnetic_displays/products/page-10/electromagnetic_status_indicators.html
but come on , this is instructables we are trying to make things from scratch, so we will be making a flip-dot from scratch, firstable some theory about how flip-dots operates you can take a loop to this website :http://www.flipdots.com/EN/electromagnetic_displays/principle_of_operations/index.html
For Building the eletromagnet you will need :
- a insulated copper wires such as magnet wire ( a thick one, so you can avoid that magnet gets hot )
- a metalic bolt
- a small round regular magnet (9.5 mm x 3.2 mm) ( can be found here : http://www.emovendo.net/magnets/discs/
- the support ( print the attached templates and cut them, and then glue them together )
Before getting to the exact building instructions i have to mention a couple of things, we are making an electromagnet as a part of an electronic circuit, it means that we have to take in consideration the Current going though the magnet, the resistans
needed and not least the pulling force of the magnet
, so it can match the regular magnet force we bought from the website, for that :
For the current
The LED are limited to 20 mA, wich will not be enough to drive our electromagnet, that's why we are going to use a higher current driver part like a ULN2803
with its own current limit resistor for the magnet, The number of windings & wire guage & the core you use will all impact the impedance of the resulting coil & hence its current draw.
For The resistans
you can do it experimentally - find a higher wattage variable resistor, put it in series with the supply, the coil, and the transistor, with the NPN transistor like the ULN2803 being the bottom of the string going to ground.
Add a resistor to ground to an input pin, and a switch to +5 so you can make it momentarily high to turn it on.
Dial the resistor to highest resistance, and slowly bring it down until you get your response, or until something smokes ! .. Oooops !
For the Pulling force
Magnetic force = I * N where as I is current and N is amount of turns
So Now that we have an idea what we need lets make our flip-dots ....