MAX5389 resetting by noise

[aless2056]

Guys, I made a simple project with a PIC16F877 and a MAX5389, which is a digital potentiometer. I'm just connecting the UP/Down and Inc terminals directly to the PIC.

Both the PIC and the MAX5389 have a 100nF capacitor next to the VDD and GND pin.

The PIC also drives a transistor, which drives a relay to activate a contactor.

It doesn't happen every time, but sometimes it happens that when activating the contactor, the MAX5389 resets and returns to the average resistance value it has when it is initialized (on power-up).

How can I resolve this?
Swap the 100nF capacitor for another one?
Also include capacitors in the two connections between the PIC and the MAX5389 (On the connections with Up/Down and Inc).

[free_electron]

the peak current in the relay coil creates enough of a power dip to reset the processor / max5389. you need to isolate the relay coil and provide a buffer.