Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "lcdpublishing"
<lcdpublishing@...> wrote:
...
> Not sure what a brushless motor is, but if it can be machined, I can 
> probably make one :-)  Any links to information about making them?

An excellent source of info, plans, help, etc.:
http://groups.yahoo.com/group/lrk-torquemax/

If you have a computer (snork) then you have at least 5 brushless
motors: hard drive, floppy, CDRom drive, CPU fan, power supply fan.

Almost all motors in electronics are brushless. CD and DVD, VCRs,
camcorders, etc.

The concept: The center rotor and its windings becomes the stator. The
outside stator and its magnets becomes the rotor. Now rather than
mechanically changing contacts via rotation past brushes, voltage is
electronically switched between windings. Some kind of current or
magnetic sensor is used to determine proper phasing.

It is sort of like driving a 3 phase stepping motor. Well, a lot like
it, actually.

Easiest way to see what is going on is to pull apart an old 3.5"
floppy drive and look at the motor driving the disk. In that case it
uses a flat rotor/magnet assembly with 4 poles, and a flattened 3
phase rotor (usually with 6 windings, 2 per pole). If you have a dual
trace or more O'scope, you can observe drive phase on the windings.

The toughest part of building a brushed electric motor IMHO is
balancing the rotor. Brushes waste more power than you probably think.
A big issue with high RPM brushed motors is that the windings may
deform and throw it out of balance. With a brushless motor with the
rotor outside, no problem with windings throwing things out of
balance, and the shell can be made -very- strong to contain the
magnets under high RPM.

They also don't generate the loads of electrical noise that brushed
motors tend to generate.

Steve Greenfield