In an Arduino based pump controller I am using a 30 amp magnetic contactor with a 120 VAC coil. I put 2-10 amp (1N10A10) diodes across the coil in hopes of suppressing high voltage noise at coil shut off. I tied cathode to cathode of the diodes and relied on reverse breakdown voltage to be reached, go into conduction and kill the spikes. Did not work well enough. I have ordered some 1.5KE250CA TVSs (transient voltage suppressor) in hopes that they will perform well enough when merely tied across coil input lugs. Someone mentioned snubber circuits. Apparently a tuned RC circuit which will suppress noise. The TVSs should be here in a couple days.As noisy as the contactor is, I think i may have to install a grounded metal box around various components in order to keep noise off data lines. Any bullet proof methods out there? Adequate yet simple.
