2 added 403 characters in body
source | link

Very simply, you can use a single pole, double throw relay. This has two outputs: one is normally open and the other is normally closed. Both will not be energized concurrently.

EDIT (based on Chuck's comment): In some applications, in which turn-on and turn-off timing is critical, you need to decide between a "make before break" and a "break before make" type of SPDT relay. With your 'bot application this timing difference shouldn't be critical, but if you want to be sure that one action occurs before the other, you can enforce that with proper selection of the relay.

Very simply, you can use a single pole, double throw relay. This has two outputs: one is normally open and the other is normally closed. Both will not be energized concurrently.

Very simply, you can use a single pole, double throw relay. This has two outputs: one is normally open and the other is normally closed. Both will not be energized concurrently.

EDIT (based on Chuck's comment): In some applications, in which turn-on and turn-off timing is critical, you need to decide between a "make before break" and a "break before make" type of SPDT relay. With your 'bot application this timing difference shouldn't be critical, but if you want to be sure that one action occurs before the other, you can enforce that with proper selection of the relay.

1
source | link

Very simply, you can use a single pole, double throw relay. This has two outputs: one is normally open and the other is normally closed. Both will not be energized concurrently.