Re: A LEGO double-throw switch?

On Mon, August 22, 2005 2:05 pm, Brian Davis wrote:
>    So I've got an application where a forklift loads a crate onto a conveyor
> belt. I could then start the conveyor belt up by having the forklift throw a
> polarity switch. What I would *like* is that when the crate gets to the other
> end, it somehow stops the conveyor motor again, (here's the tricky part),
> leaving the system in a state where the next forklift delivery can re-trigger
> the whole system from the "front end", as it were.
>    Oh, did I mention I wanted to do this with just polarity switches, no RCX or
> other "intelligent" systems in the loop?

Ok, Here's a partial solution (assuming you don't want to mechanically link the ends
together).  Given:
Polarity Switch 1 - rotated forward by Forklift
Polarity Switch 2 - rotated forward by crate when it arrives at the end
Motor - located by switch 2  (could be on either end, with no difference in wires
required, however the resistance in the wires could cause a voltage difference
across the motor...)

Connect power directly to switch 1 & switch 2.  Connect one side of a wire from
switch 1 to the motor.  Same for switch 2.

When the switches are in the same position, the belt will not move.  When in
opposite positions, it will run (some direction)

Two problems:
1) Half the time, the motor will run backwards (can be fixed using diodes)
2) The "dead" zone where a crate can turn "off" switch 2, but not move it all the
way to the "reverse" direction.

I'd suggest mechanically linking the switches (making it so the same switch is
triggered on both ends)

Get it?

Steve