I am a beginner to relays and Raspberry Pi so please pardon me if my question sounds naive. I am trying to control 4 DC motors using relays and raspberry pi. I have decided to use an external supply for the relay. My doubt is how to connect the external power supply with the relay. I know that connecting the JD-VCC and GND to the external power supply would allow to me power the relay separately but I have also seen videos where the external power supply is directly connected NO pin of each of the relay. Image shown for reference: Power source directly connected to relay

Sorry for the poor image quality but the youtube video showing the connection is shown here. I wanted if there is a difference between connection as shown in the image and connecting the supply to JD-VCC and GND. Also which is the best way to do it. Thanks in advance!!

  • Hi @Prashant, your question about JD-VCC is a bit complicated. You might like to read the following to get started: (1) Appendix C of my answer to the question: ( raspberrypi.stackexchange.com/questions/99988/… ), (2) The paragraphs on using the Forbes recommended relay of my answer to the following question: ( raspberrypi.stackexchange.com/questions/95862/… ) / continue, ... – tlfong01 Jul 18 '19 at 5:09
  • Now let us look at the Rpi JD-Vcc connection schematic, as shown in my second answer referred above: ( imgur.com/gallery/DVohaVG ) You need to read the schematic very carefully for at least 5 minutes, before I move on, ... /to continue, ... – tlfong01 Jul 18 '19 at 5:20
  • In the above schematic, JD-Vcc jumper is removed, and (1) Opto coupler is powered by 3V3, (2) Songle relay switch is powered by 5V. Now suppose we have a similar low trigger relay, but without JD-Vcc jumper, Or we can consider that even if we have JD-Vcc jumper, this time we insert the jumper, so that both optocoupler and relay switch are connected by 5V, as show in the following picture. (imgur.com/gallery/GwBdP5Y ) /to continue, ... – tlfong01 Jul 18 '19 at 6:12

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