Re: When is "off" off?

In lugnet.robotics, Mitchell Lichtenberg wrote:
> If I attach a motor to a battery box and twist the motor arbor I get resistance
> EVEN if the battery box is switched off.  This means that the current,generated
> by the motor, is getting through, correct? Is the current just bridging the
> contacts or is it going through to the batteries?  Is there a 'drain' condition
> if motors are left plugged into battery boxes or RCXs?  I know the gurus out
> there can give me an answer.  Thanks.

The RCX has the capability to place a resistance accross its output terminals.
Removing that resistance provides the free spinning behavior enabled by one of
the programmable features. Inserting the resistance gives tighter control of
motor speed. I don't have a schematic handy, but there's no conceptual reason
why providing resistance across an output has to require power from the supply.

-Ted