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.


  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.