So. I have a 1 Channel 5V relay from a starter kit and I cant turn it on or off.

I saw a bunch of tutorials but in every one the labels on the relay are such as VCC, GND and so on.

My relay its labeled like: S, +, -

I have little to know idea about electronics and I dont know which one goes to the VCC pin, which one to the ground, and which one to the GPIO.


  • VCC = + (5V), GND = - and S = Signal from GPIO (3.3V). – kwasmich Mar 7 '19 at 10:18
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    Part number and/or datasheet? – Roger Jones Mar 7 '19 at 10:25
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    Is your relay active LOW. Lots of the cheapo Chinese ones from the auction site work that way. – Dougie Mar 7 '19 at 10:45
  • Not enough info. A few comments that might help you get the answer you want: 1. Read How To Ask a Good Question, 2. edit your question to include a link to a spec sheet for the relay you're using, 3. try using the schematic tool to frame specific interconnect questions. – Seamus Mar 7 '19 at 20:11
  • @kwasmich is right. I got it working – Asier Paz Mar 8 '19 at 6:06

It is a 5 volt relay and you try to turn it on with 3,3 volt!

You need a "level converter" that can elevate the 3,3 volt signal to 5 volt.

| improve this answer | |
  • Actually no. I am now able to toggle it with the mappings @kwasmich gave me. – Asier Paz Mar 8 '19 at 12:15
  • Then you are lucky or you have a relay module, not a 5v relay. – MatsK Mar 8 '19 at 15:30
  • It is a module for raspberry pi. – Asier Paz Apr 4 '19 at 13:51

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