US Patent 10021842 Irrigation controllers with enhanced alternating current switching devices

Some embodiments provide irrigation controllers, comprising: a transformer configured to step down a voltage producing an AC power signal; a live AC line and an AC common line coupled with the transformer; a plurality of AC switches coupled with the live AC line and configured to selectively pass the AC power signal to one or more valve solenoids such that the one or more valve solenoids are effectively coupled across the live AC line and the AC common line; an impedance element coupled serially on the AC common line with the transformer, wherein the impedance element comprises an inductive reactance and a resistive component, and the impedance element is configured to increase overvoltage protection between the transformer and the plurality of AC switches increasing an effective voltage tolerance to the overvoltage conditions at the AC switches; and a controller configured to selectively control the plurality of AC switches.