I purchase V 4-Channel Relay Module Low Level Trigger with Opto coupler for Arduino
What kind of External power supply need to this relay. It work with 5 volt but how much current need ?.
And how do I connect it together with Arduino board ?
If it's typical of many Asian e-bay type relay modules the hook-up would be as follows:
1. ground to ground
2. 4 relay channel input pins wired to 4 arduino digital output pins
3. Board Vcc power to arduino 5V pin, 4 relay coils won't 'overload the Arduino board's 5 vdc.
4. The board my have a movable jumper for power, be sure it is proper position to be powered from Arduino.
5. As you stated in your coding a digitalWrite(pin#,LOW) will turn on the relay channel.