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Is it possible to use an external adapter for the 5V, so connecting the + from the adapter to VCC of the relay and the - of the adapter to GND of the relay. Then IN to GPIO27. Setting this low will trigger the relay? I tried, but it seems not to work. I ask this, because I want to use a NO/NC magnetic door switch. Thanks in advance for your answer.

Yvonne

Lodv
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    Insufficient information to make any meaningful answer – Milliways Aug 27 '19 at 07:50
  • @Lodv, Ah let me see. I googled and found the following: "Using single 5V relay (jqc-3ff-s-z) - Safety Advice Required": https://raspberrypi.stackexchange.com/questions/73311/using-single-5v-relay-jqc-3ff-s-z-safety-advice-required. – tlfong01 Aug 27 '19 at 08:20
  • Yes, provided you connect the Pi ground to the external power supply ground (as well as the relay ground). – joan Aug 27 '19 at 08:26
  • @Lodv, The asker I referred above asks advice for Hesai (TongLing jqc-3ff-s-z) relay, but his connection diagram shows another relay Keyes SR1y (KY019) using Songle relay. Please confirm which relay you are using, or give us the web link to your relay.. – tlfong01 Aug 27 '19 at 08:44
  • I think that is the solution sharing ground. I found this article: https://majenko.co.uk/blog/importance-sharing-grounds Thank you all for your help. – Lodv Aug 27 '19 at 14:31
  • I made a sketch, but I don't know how I can attach it to this comment. I'm still confused. How can I show it in my jpeg file to you? – Lodv Aug 27 '19 at 18:56

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jqc-3ff-s-z is NOT a relay, it's a "relay module"!

The relay module has a driver circuit included on the modules board.

And yes it is possible to use a external power source to the relay module (jqc-3ff-s-z).

Just remember to:

  • Connect GND on the relay module to both the Raspberry Pi and the external power source.
  • Connect VCC only to the external power source.
  • Connect IN to only the Raspberry Pi.
MatsK
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