it might be helpful if i list some more specific details about what it is im trying to do.
basically this is for a reptile enclosure to operate a water misting system. the misting pump is for intermittent use only, with 1 minute off for every 2 mins on.
i have a humidity controller which has a 230V plug on it. you plug the misting system into the plug, and the controller into the wall socket. it monitors humidity and when it drops below a threshold the plug goes live, powering the misting system, which then pumps water in until the upper threshold is reached, at which point the controller switches the misting system off.
the issue here is that the controller outputs constantly until humidity is reached. if it never reaches it or takes ages to get there, the motor could potentially burn out since it is only intended for intermittent use.
what i need is a circuit which ensures the motor is never allowed to run for more than 2 mins without giving it 60 seconds rest in between. a timed relay could work with the 2 minutes on part, but after the 2 mins are up it will switch off and then theres no way to switch it back on again unless the input goes dead and then live again. which it never will if humidity hasnt been reached within the 2 mins!!
im wondering if using 2 timed relays and a relay could work though....
controller feeds signal to timed relay 1. output goes live for 120 secs. when the output goes dead this then triggers a 2nd timed relay which goes live for 60 secs. when the 60 secs is up the output goes dead. there is then a relay on the main input signal to timed relay 1 which can only go live when timed relay 2 is dead. this means that so long as there is still a signal from the controller, the 2nd timed relay would re-trigger the 1st one. in my head this would work perfectly, in reality maybe not. any thoughts? id use the controller to supply the constant 230V feed, this way when the controller switches off (e.g. humidty is reached) so does the whole timing circuit, meaning it doesnt carry on for the full 2 mins even if humidity is reached after 20 seconds