I'm trying to build an auto water change circuit.
i don't know anything about electronics so please make like your talking to a child
i have been playing with eagle cad and pcb making so i'm good there.
the set up is as follows i want a pump in the tank to come on and pump until a low float switch is triggered then i want another pump to come on a pump water back in until a top float switch is triggered then i do not want the pumps to turn on for a set number of days or hours that can be changed any time.

it this gonna be crazy hard or is it easy accomplished

 

the process could also be triggered by a switch whitc would be easier than a timer.
i'm just not sure how to prevent one pump from turning on when it is not supposed to.

 

my thoughs so far is for a switch to start the first pump and for it to continue to pump until both float switches are down. then for the other to pump until both switches are up.
i'm thinking latching circuits are needed ?

 

You could do it with a single float switch. Most float switches that I have dealt with are snapping action type, meaning that it takes significant force to make it switch, and then when it switches, it snaps over and then requires significant force in the other direction to move it the other way. Yor float is attached to a metal rod which moves up and down, and you set the depth for switching on the way up and the way down with adjustable stop on the rod. The timing can be accomplished with a lamp timer. You shouldn't need to design any circuits for this at all.

 

anybody able to help

 

>>>then i do not want the pumps to turn on for a set number of days or hours that can be changed any time.<<<

Why? its not a good idea to put a timer on an auto top off setup.. Why you ask....Because evaporation rates are changing all the time. Putting a timer anywhere in that system could cause something to run dry or loose too much water to evaporation..

I assume you want one to pump water from your top off tank in your sump (or display tank if you don't have a sump) and then one to refill the top off tank..Is that correct?

You can also setup a 100% mechanical solution if you want too.. http://reefbuilders.com/2009/05/26/diy-tea-jar-auto-topoff/