How much voltage/amperage is needed to power an electromagnet the size of an apple

Question

i plan on making an electro-magnet powered by solar cells. the cells produce 0.3-amps at 0.55VDC in full sunlight, how many of them or how many volts/amps does a smallish electromagnet need to have a magnetic feild, it doesnt need to be a huge magnetics, but it needs to be noticable.

Answer 1

That is a pretty large electromagnet for this kind of project.

The answer depends on how fine the magnet wire is - higher resistance from finer wire, but more coils in the same space so stronger magnetic field.

Answer 2

i believe you are going about this design completely backwards. find a suitable electro magnet and THEN design a way to power it. electromagnets can be pretty power hungry. it may be difficult to achieve with solar power. a good electromagnet can be found in pinball machines they are quite powerful. a standard one is about the size of a snuff can (anyone remember snuff?), and is strong enough to brake a finger. the ones i used ran on 1.5 amps and fifty volts. so you would need a string of 100 cells in series. you will need to put five of these strings in parallel to be able to power that electro magnet. that is 500 cells to power a common size electromagnet.

you will need  to do a little research to find one pretty small. think about braking open a solenoid for the electromagnet. when you find something that will work give us the specs for both items and we will tell you how to hook it up.

sorry it couldnt just be a simple answer. those specs are for keeping it running if you want to generate power over time and store it for a minutes use that will be much easyier. use a small cell array to power a charge pump that charges a 75v 3300uF cap to 50v that should run it for  about a minute.

edit: ok my fault. but you wont be able to generate a noticeable field with that. you will need several windings. electromagnets are something that is better to buy than make.if you just want to use a dozen windings to make a field that will move metal shavings on paper that will probably work. you will want to use some type of high resistance winding to prevent overloading the cells. you will want to get it to about 20 ohms, then use the setup described below. a cap and diode wont be necessary with a home made coil.

how about this:

http://www.jameco.com/webapp/wcs/stores/...

put put 6 cells in a series string; 2 parallel. that might work in direct sun light. if i were building it i would use a string of 7; 3 parallel. also put a diode reverse bias across the coil. this will keep the EMP generated by the coil from damaging the solar cells. if you have trouble engaging the coil add a large cap parallel to the coil (at least a 20vdc cap). when the cap has charged, it should be able to supply the large spike of current needed to fire the coil. if it still wont engage use a larger cap (more uF, not Volts) until it works. if you have trouble you can post here again or just email me.

have fun.