Relays board unexpected behaviour

Projects Programming
1

Hi,

I have 8 relays board that i'm controlling using RS485 Device

I powered the relays with external 5v 3 amp adapter, and the arduino mega with 9v adapter

The problem is when the 8th relay is opened it closes the whole board

Scenario :

Open Relays from 1 to 8
Relays opening and clicking naturally 1-2-3-4-5-6-7
and when 8 should be opened, but all relays closes instead i have no idea why

should i connect the ground of the arduino to anything or what is the problem

the connection scheme is
5v adapter to VIN and GND in the relays board
8 signal inputs to 25, 26, 27, 28, 29, 30, 31, 32 pins

2

Might be a power issue. What happens if you just open relay 8?

3

wildbill:
Might be a power issue. What happens if you just open relay 8?

It doesn't connect to a specific relay, any 8th relay i open all relays are working if i open any 7 relays when i open the 8th relay it close all the relays although i used a multimeter to calculate the signal voltage it shows 4.85 volt

4

Sounds like power; I'd try a beefier supply.

5

the problem solved by connecting the ground of arduino with relay board ground