user36862: I have this relay module. I don't understand what is a role of the jumper on it (for now it's shorting the jd-vcc (what??) and vcc pins).  


user37523: The jd-vcc pin can be used to power the relay coils using a separate 5V power supply. Why would you want to do that? Each relay coil draws about 73mA @ 5VDC when energized. Theres a circuit schematic on this website: http://howtomechatronics.com/tutorials/arduino/control-high-voltage-devices-arduino-relay-tutorial/

36862: <p>I have this relay module. I don't understand what is a role of the jumper on it (for now it's shorting the jd-vcc (what??) and vcc pins).  </p>

<p><a href="https://i.stack.imgur.com/HF3MN.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/HF3MN.jpg" alt="Relay"></a></p>
 37523: <p>The jd-vcc pin can be used to power the relay coils using a separate 5V power supply. Why would you want to do that? Each relay coil draws about 73mA @ 5VDC when energized. Theres a circuit schematic on this website: <a href="http://howtomechatronics.com/tutorials/arduino/control-high-voltage-devices-arduino-relay-tutorial/" rel="nofollow noreferrer">http://howtomechatronics.com/tutorials/arduino/control-high-voltage-devices-arduino-relay-tutorial/</a></p>
