5 Replies Latest reply on Nov 19, 2016 3:53 PM by phoenixcomm

    Arduino Low Voltage Trigger(Relay) question.

    spanevelo

      To make this very long story short, all I want to do is to turn a relay on and off using an arduino.

      I bought this relay from ebay(12V 1-Channel Relay Module Optocoupler Low Level Trigger Expansion Board Arduino | eBay ).

      And I got the wired like this:

      Relay   -  Arduino

      VCC to    5v

      GND to   GND

      IN      to   Digital OP 7.

      I see the LED on the Relay goes on every time the relay was supposed to change it's state, But when I check with the voltimeeter the NO never closes and the NC never opens.

      A'm I missing something?

       

      And this is the code:

      int PowerSwitch = 7;

      int PowerButton = 8;

       

      void setup() {

            pinMode(PowerSwitch, OUTPUT);

            pinMode(PowerButton, INPUT);

            Serial.begin(9600);

      }

      void loop() {

       

              digitalWrite (PowerSwitch, HIGH);

              Serial.println (" ON ");

              delay(10000);

              digitalWrite (PowerSwitch, LOW);

              Serial.println (" OFF  ");

              delay(10000);

      }

      s-l1600.jpg

        • Re: Arduino Low Voltage Trigger(Relay) question.
          beacon_dave

          You appear to be trying to power a 12v rated relay coil from a 5v power supply.

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            • Re: Arduino Low Voltage Trigger(Relay) question.
              spanevelo

              Hmm.. Looking at it now, It sounds like a really stupid question.

              Although.. The way the seller explained was that it would handle  12v on the NO & NC side.. not that it need 12v for input.

              I'll look at the data sheet.

                • Re: Arduino Low Voltage Trigger(Relay) question.
                  jw0752

                  Hi Marcus,

                  Based on the marking on the relay itself you will definitely need at least 10 volts and preferably 12 volts DC to run the board and relay. Your Arduino will be able to power the opto-isolator. It is likely that there are boards like this for 5 volt operation but you may be expecting too much if you want the little regulator on the Arduino to supply this power. It is best to have a separate power supply from which you should be able to power the board with 12 volts and the arduino with 5 to 9 volts.

                  John

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                  • Re: Arduino Low Voltage Trigger(Relay) question.
                    phoenixcomm

                    relay.gifOk, this is now Back to College: Relay 101;

                    Now on the right you will see a relay diagram. we are only interested in

                    • The Coil:  Supply Voltage for the relay. 5, 12, etc and is the coil AC or DC.
                    • The Contacts: how many and for more advanced you will also want the form

                    The Coil is voltage is the voltage you must have to energize the coil. Relay_Diagram.jpg

                    The Coils contacts ratings are in voltage and amperage

                    So when the seller said: "that it would handle  12v on the NO & NC side.. not that it need 12v for input."

                    he was referring to the voltage of the contacts. on spec on top of your relay said: "10A 250VAC, 10A 125VAC, 10A 30VDC, 28A 28VDC" as well as SRD-12VDC-SL-C and Songle.

                    I found the spec sheet for the relay here: www.songle.com

                    SRDXX VDCSLC
                    Model of relayNominal coil voltageStructureCoil sensitivityContact form
                    12S:Sealed typeL:0.36WC: form C

                    I also found this diagram of an arduino hooked up to a relay. you will notice that this relay is 5v. So all the arduino does is energize the relay's coil which change the relay's contacts while the battery at the bottom powers the LED.

                    FINS

                    CAH

                    Relay12v.jpgrelay-open.png

                • Re: Arduino Low Voltage Trigger(Relay) question.
                  phoenixcomm

                  I agree you can't run a relay with a 12volt coil on 5 volts.. you need a relay that has a 5volt coil.

                  5v relay.jpgPlease make sure that the relay board is OPTO-ISOLATED as the back emf of the coil could wipe out your Arduino. Even though your board seems to have a protection diode (the glass thing near the green diode) for the back emf. I use the relays to drive lights in my simulator and they run on 24v, ouch.

                  CH

                   

                  5V Relay Module Board 10A Opto Isolated For Arduino

                  2 Channel 5V Relay Module Board 10A Opto Isolated For Arduino | eBay

                  5v relay.2.jpg

                  2 of 2 people found this helpful