16X2 LCD Display Problem

Dear all,

I am trying to control a 1hp motor through the 230VAC contactor which is controlled by a 12v relay supplied with 12v 1A SMPS Adapter.

Everything works fine if i disconnect 230VAC Contactor. but when i power it up, the lcd displays random characters and after few attempts all the disappears. however arduino works fine as the logic executes perfectly.

When i checked voltages across the lcd supply pins, i obeserved that there are some spikes that are generated whenever the contactor turns on or off. measured voltages are nearly 17v DC, 6v DC, 10v DC etc. I have traced the problem but don’t know how to resolve it.

I have attached a circuit diagram of the relay and contactor connections for the reference.

Note:

  1. Earthing and all the ground pins are common.no earthing problem is found.
  2. No motor trial is taken as the problem appeared when contactor connected.