The problem with analog type controllers for what you need is the trip of the device to be switched and the electrical noise that it generates and at the point close to when the on or off condition is met and what is called differential. It is difficult to explain in words to people who are not on the subject but the advent of digital in such devices was a "blessing." I upload the scheme of one that they sold in the form of Kit to assemble a few years ago and it is simple since they discontinued / replaced it. [url=/ver-adjunto/aHR0cHM6Ly9jZG4ueW9yZXBhcm8uY29tL3VwbG9hZHMvZGVmYXVsdC8wMDAzLzE3LzE3My03MzI3Mi56aXA=] [img/gta./gta/bta.png/bta.png/bta.png/bta.png/bta.png/bta.png/gta.png