a few questions for you circuitry guys, need help

[noobtothereef]

I looking to build a controller to control a linear actuator, it just has a positive and negative wires and is 12v. It needs to extend for about 1 second, then hold that position for x amount of time and then retract for 1 second and then hold for x amount of time and repeat. How can this be done? To switch dirctions the polarity would need to be switched as you probably allready know. Im gessing some timed relays or??? Im boggled with something this complex

Im guessing its gonna need a programmable relay/timer like this?

http://www.ingramproducts.com/Timers_Programmables-Multi_function_Digital_Timer.html

so the cycle will look like this

on 1 second------ off for 10 seconds-------reversed polarity on for 1 second-----off for 20 seconds
and repeat continously

[walkerbrody]

Using the linear actuator for rotating a powerhead? I did close to the same think a couple years ago using a pneumatic linear actuator with a spring on the shaft. I had an air pump extend the actuator. I had the pump on a timer, when it turned off, the spring would slowly return the actuator to the start position. I varied the speed of the movement by using needle valves on the air line.

[Mike31154]

Does the linear actuator have internal limit switches that cut power when it reaches the end of it's travel each way? If so, you may not need a controller, but simply a double pole, time delay relay. So in the NO (normally open or deenergized) mode, the actuator will run in one direction until it hits the limit, after the desired delay (relay spec), the relay contacts close and provide reverse polarity to run the actuator in the opposite direction.

[kcress]

Mike has a good description of a method.

What I'd do is pick up one of these:
http://www.factorymation.com/s.nl/sc.2/category.11443/.f

They're less money than a programmable relay and they're infinitely more flexible. You will need to fuss with the programming a little.

You can DL the software for free and run everything on the simulator.