noice microcontrller

Hi
I made PCB with arduino uno. It has inputs push-buttons, temperature sensor and four outputs (mechanical relay).The PCB has input stage transformer 220/12 V. It has voltage regulator 5V with two block capacitors of 100 nF (placed on input and output of voltage regulator). Also has electrolytic capacitor 4700 uF.
The mechanical relays switch the three contactors with coil voltage of 220 VAC.
All works fine. Only sometimes when all contactors switch off in the same time the ATMEGA328 resets by itself. It is because of the collapsing electromagnetic filed.I search the web and I found that I must put on the voltage regulator in parallel three block capacitor of 1,10,100 nF. Also in parallel of the coil of the contactor I must put the capacitor of 0,22 uF , 500V .
Also near the uC I will put in parallel three block capacitors between VCC and GND value (1 , 10 , 100 nF).
Is this is enough for block the noice which resets the uC or I must do additional things.
Regards
Riste

Also put a diode in reverse. It is called free wheeling diode. Choose proper current rated diode.

hi ,
it is useful to put some diodes in paralel with the rellay coils to kill auto induction spikes when turning them off. The noise produced by the contactors normally should not reach the mcu

Show your PCB. It should have ground poligon for EMC protection.

Easyrider83 said:

Show your PCB. It should have ground poligon for EMC protection.

Click to expand...

I do not have ground polygon for EMC.
Can you show me pictures of this polygon how to make it.
Regards
riste

HI
How to make ground polygon for EMC. Can you send me some example.
Regards
riste

First one without ground poligon

Second one with

What did you put at RESET signal?

you must put a pull up 10k and to cappacitor 100nf and 10uF close to the pin.