Electronic Circuits and Projects Forum

I was also wondering what if I wired the motor to a potentiometer and a rechargeable battery. Then let the turbine turn the motor while the resistance in the potentiometer is high then to slow down the motor, lower the resistance. Would this work or is it bad to do this?

The more important question is how big is this turbine? Physical size and driving method that sort of stuff.

As far as low speed high torque while maintaining high relative efficiencys its going to be difficult to beat simple hydraulic pumps or motors that will work in direct drive applications.

That's pretty big. Your motor might be undersized.

Here's that image again, hope it works this time. I'm just trying to show you the kind of gear ratio you will need:

brushless 003b.jpg

So, you need to get it spinning pretty fast. But you CAN feel the drag, even with just ONE of the 3 windings shorted!


Maybe what you need is a "powdered-core" brake or clutch. These have iron filings between rotary poles of a magnet. Turn the magnet on a little, some filings start to stick, you get some drag. Turn it on full, and the whole thing locks up solid.

Here's a link to some big ones, so you can see -

http://www.oocities.org/hankfu/indexEN.htm

This place has several sold as surplus, maybe one is small and inexpensive enough for what you need. Type "clutch" into the search box -
http://www.electronicsurplus.com

If not, maybe what you need to do is drive a permanent motor backwards. But I think maybe that "outrunner" brushless will do what you want, if you just gear it up. They sell gear assemblies like the one above on hobby sites - these motors actually spin too fast for most props.

It is about 15 inches in diameter and an average chord length of about 1.7 inches. Shaft diameter is 1/2 inch.

Being that small I would recomend just using a common stepper motor for the generator. They com in all sorts of sizes and can usualy be found for next to nothing.

How would you go about wiring the stepper motor to get the braking effect?

Most stepper motors are either two phase or three phase so you have to either run each phase through rectifiers or set up each winding with its own load.

Either way its not hard to work with.