Hello, I am a new user here but have found links to this site in many of my Google quests so I thought this may be the place to start a more focused search for information. I am doing a project with my son, we have created some spinning discs using magnets as a power source. I am interested in attaching a small electric engine (or coil) to produce electricity that could power a small LED or compact fluorescent light bulb. I am assuming it would be better to buy a small engine and reverse it than to build the coil because it would probably be better produced and more efficient. But I am not completely understanding how much torque and rpm's are needed to generate electricity from said motors and what tools should be used to measure the performance of the set-up. I was considering buying the Greenlee DM-300 multimeter because of its low voltage accuracy and maybe trying this method of measuring rpm's <http://www.fastcharged.org/electronics/handyrpm> unless there is an easier cost effective way. Also are their numbers I should look at to find out what rpm and torque is needed to spin the coil? Can anybody recommend a good engine for this? Thanks much in advance.