how to omit noise of LCD driver in a one layer PCB board

[matin-kh]

hi every one,
In a project in a PCB board I use a nokia 1202 LCD, an atmega8 and 5 relays. the PCB board is connected to a 220 volt ac signal which with some diodes and resistors and capacitors it has changed to 20v DC and relays are connected to this voltage then with a LM317 20v is changed to 3.3 volt for vdd of micro and LCD, with generate a little noise the characters of LCD will be damaged and I think absolutely it's because of 220v ac signal noise on driver of LCD but i don't know how to solve it could you please help me?
with best regards
matin

 

[D.A.(Tony)Stewart]

Even though logic runs on 3,3V normally LCD analog signals are differential with analog bias voltages in the range of 12V. It seems these are the ones getting interference, not the logic or SPI interface.

Consider interface shielded wires, ferrite choke sleeve, ground plane, check all analog signals and voltages and ensure Analog ground is clean relative to analog driver. Imbalance from stray EMI can induce noise.

But scoping analog signals on LCD will show the problem, or show us.

 

[marce]

EMC, where to begin, without the circuit and layout we can only guess...
Here is a good place to start on EMC problems
http://www.hottconsultants.com/