Thanks a lot, mate! Placing the diode across the solenoid did the trick! It's much more stable now. I think I just need to place the diode even closer to the solenoid to completely get rid off the problem. Right now the diode is about 30cm away from the solenoid.
I have another similar circuit with a LCD and 256 relays (to control 256 electronic solenoids). This setup also experiences the same rubbish character problem on the LCD, so I will need to place the diode across all the solenoids as shown in the attachment. Is there an easier way to place the diodes? It's quite a bit of work to cut the wires and solder the diodes on all 256 solenoids. Thanks again!
