Any way to flip motor direction when energized?

[pjs2003]

Is there a simple way to switch the direction of a motor when powered-up? I am working on a home-automation project whereby I have a 12v motor operating off of a timer (basic off-the-shelf digital timer). When the timer switches on the motor spins foward. However, I am trying to make it spin backward the next time the timer switches it on, and continue flipping directions each time the motor is powered-up. Is it possible to do this with a type of relay or combination of basic electronic components, or does it require a special circuit?

Any help is much appreciated.

 

[ante]

Perhaps you can use a highbeam/lowbeam automobile relay.

Ante :roll:

 

[pjs2003]

Thanks for the reply Ante, but I think I figured out what I need. I'm pretty sure that a bi-stable (or latching) relay will do the trick. This was what I had in mind, but I just didn't know the name of it. Man, it took me so long to find it because I just didn't know the right words to put into search. Finally, I tried putting in flip and relay and eventually I got to it.

 

[udi_hakim]

If its a simple DC motor you can use latch like the 74HC573, for the first direction just make the latch to output "10xxxxxx" and for the second direction make the latch output "01xxxxxx" (the motor will use the first and the second outputs).
Im sure the latch can't supply the sufficient current to drive your DC motor so make an AMP circuit that the latch will trigger...

 

[panic mode]

You can use simple H-bridge or relay to change direction.
If there are no delays between forward/reverse directions,
(continuous duty for motor) you can simply use simple
astable like 555 to turn on the relay. By using pair of diodes and
potentiometer, you can set any ratio for FWD/REV times.

 

[Klaus]

Use the circuit that Panic Mode supplied but replace the relay with a 'latching' type. No need to make this too complicated with lots of electronics
:wink:

For those who do not know what a latching relay does: it has a magnetically biased coil that keeps the contacts at whatever position they were in before the relay coil was disconnected from power.
Upon the next switch on cycle the relay contacts will flip and stay that way until the next cycle.
So, switching the relay on and off repeatedly will cycle the contacts at half the switch rate.

Klaus

 

[pjs2003]

Thanks for the expert help guys! I really appreciate it!