I have complete home automation project and control through Blynk. When Arduino Power on all relay on, then relay on/off through blynk app working as well as. Why relay on when power up? In time button off position in blynk app.
Relay power connect from Arduino +5Volt.
this situation relay must connect external power or not?
Here's the problem.
Because you have told us nothing about how you have wired up your system or what components you are using, we simply have no idea what the problem could possibly be.
Only when you reveal all the circuit diagrams and the specifications of the parts (by Web links would be the easiest) you are using, might we start to make guesses.
How can we possibly help you without seeing the code and the hardware.
Read the "how to post" sticky that can be found on every main page.
Relays or relay module.
'on' for a short time or until you change state.
If 8-relay module with opto couplers, then did you enable pull up on the pins in setup(), before pinMode?
digitalWrite(relay1Pin, HIGH); // or digitalWrite(relay1Pin, INPUT_PULLUP);
// more relay pull up code here
//more relay pinModes here
How did you power the unspecified Arduino.
The 5volt pin can't power many relays.