hi
I desinged a pcb with 1000uf on regulator input and 100 nf on its output, there is also 100nf connected the MCU VCC close to it. the circuit is working fine with dc motor and ac lamp but the problem appeared when i connected small ac motor(grill motor). it disturbed the MCU code and take random actions and disturb external interrup

 

You need to post a schematic of your setup. We have no idea how you are switching the AC supply from the logic output.

Les.

 

i attached MCU board and relay board

 

I suggest connecting a contact suppressor such as this across the set of contacts that switch the supply to the motor. If the motor is a series wound (Universal) type then adding a capacitor of about 100nF (X rated and a suitable voltage rating for the mains supply in your country) directly across the brushes should help.

Les.

 

this is the motor used, it is ac motor 220v. Is it right to add 100nf across it?
https://www.alibaba.com/product-det...tml?spm=a2700.7724857.main07.1.6e556061pHjzRf

 

Ensure the DC power is sufficiently decoupled with capacitors and also a .1μf close to MCU power.
Do you have the frame of the motor earth grounded?
If you still get random interference after fitting snubbers, you could try earth grounding the MCU supply if operating in a country that uses this type of service.
Max.

 

That is an induction motor (Probably shaded pole.) so it will not have any brushes to generate interference. (So there is no need for a capacitor in parallel with it.)

Les.

 

what will the suppressor do? and what is its alternative if i didn't find it?
how does contacts affect the MCU circuit?

 

Ensure the DC power is sufficiently decoupled with capacitors and also a .1μf close to MCU power.
Do you have the frame of the motor earth grounded?
If you still get random interference after fitting snubbers, you could try earth grounding the MCU supply if operating in a country that uses this type of service.
Max.

0.1uf ceramic capacitor ?i already put capacitors close to MCU
i don't have earth.

 

That is a AC synchronous motor and they generally are extremely quiet, electrically speaking.
Is it while the motor is running or just when switching?
Max.

 

when switching

 

The amount of current in switching that motor should be really trivial.
Have you placed small C or RC snubbers across the relay contacts?
Max.

 

no, I didn't
what are value of c should i put?

 

Switching an inductive load (The motor.) can generate radiated electrical interference which can effect the MCU. The suppressor in the link is just a 100 nF capacitor in series with a 100 ohm resistor. If you make one then the capacitor must be X rated for that sort of application.

Les.

 

where should i connect it? between common and NO? please point on my schematic

 

The WIMA MKP/FKP metalised paper are often used for snubber apps.
Voltage rating above what it will be subjected to.
Connect across the N.O. contacts.
Max.

 

I connected 100nf in series with 100ohm across common and NO. the problem is still existed when i connect input to the relay board

 

What is the current of the motor? Probably Ma's You could look at a small SSR to do the switching.
The Opto22 modular types would be in this current range, Opto used to show the internal details for them which would enable you to build, if you so wished, If you cannot find it I can post them.
DC 5v in, AC output.
Max.

 

i think the disturbance is little frequent may be it is the random action. i think motor current is small. Is there any other solution?

 

Have you tried powering the micro from a Battery DC source to test if the interference is of mains origin.
Max.