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Need help wiring a relay please..

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  • Need help wiring a relay please..

    I bought some LEDs that I want to install as daytime running lights on my car.. I want them to come on when the car is on but go off when the headlights are on..

    I would I wire this to accomplish that?

    Thanks!
    Current Vehicle: 2007 Dodge Nitro

    Second Vehicle: Sold it :( 2005 Dodge Ram 1500 Quad Cab

    First Vehicle: 2003 Ford Ranger

  • #2
    You could use two relays. Use the N.O. connection on one to turn on the DRL's when you turn on the key. Then use another relay in series with that, but use the N.C. connection and power that relay off the headlights.

    Comment


    • #3
      Any chance you could be more specific? Pin numbers and the like?

      Thanks much.
      Current Vehicle: 2007 Dodge Nitro

      Second Vehicle: Sold it :( 2005 Dodge Ram 1500 Quad Cab

      First Vehicle: 2003 Ford Ranger

      Comment


      • #4
        http://www.autoshop101.com/forms/hweb2.pdf

        On the top of Page 9 shows a 5 pin relay, you would need two of those. They are usually good for 30A, and you can get sockets for them so they are easy to wire.

        Relay 1 DRL on (Normally Open Relay) Closes when power is applied
        Wire 86 to Ignition
        Wire 85 to Ground
        Wire 30 +12Vdc Power (Fused)
        Wire 87 Power out to Relay 2

        Relay 2 DRL off with headlights on (Normally Closed Relay) Opens when power is applied
        Wire 86 to a wire that goes hot when headlights are turned on.
        Wire 85 To Ground
        Wire 30 Power in From Relay 1's Wire 87
        Wire 87A out to DRL's + Wire

        On page 12 of the document they show Diodes to suppress the voltage spikes when turning off the relay, not a bad idea. A Radio Shack general purpose diode is fine. 1N4001 I think.

        Ground DRL's as normal.

        Is that a little more clear?

        Comment


        • #5
          With standard automotive relays a Diode is not necessary since it is already included in the package.

          Also you CAN do this with one relay. The coil of the relay needs to see negative on one site and positive on the other side.

          Using a combination of resistors and possibly a Diode or two you can accomplish the same thing as using two relays. Also if you do use two relays you can use a standard 20/30 amp automotive relay to power the lights and a much smaller 12volt relay to control the coil when the lights are on or not since the second one really doesn't need to carry any current.

          Comment


          • #6
            Originally posted by redheadedrod View Post
            With standard automotive relays a Diode is not necessary since it is already included in the package.

            Also you CAN do this with one relay. The coil of the relay needs to see negative on one site and positive on the other side.

            Using a combination of resistors and possibly a Diode or two you can accomplish the same thing as using two relays. Also if you do use two relays you can use a standard 20/30 amp automotive relay to power the lights and a much smaller 12volt relay to control the coil when the lights are on or not since the second one really doesn't need to carry any current.
            True; I also know that some newer vehicles use the existing lights (usually the high-beam at a lower intensity) to serve this function.

            Comment


            • #7
              As an alternative, you can use one heavy duty relay, and one light duty.

              Relay 1 DRL on (Normally Open Relay) Closes when power is applied. Heavy Duty Relay
              Wire 86 to Ignition
              Wire 85 to N.C. Of Relay 2
              Wire 30 +12Vdc Power (Fused)
              Wire 87 Power out to Lights

              Relay 2 DRL off with headlights on (Normally Closed Relay) Opens when power is applied This can be like a 1 Amp Relay.
              Wire 86 to a wire that goes hot when headlights are turned on.
              Wire 85 To Ground
              Wire 30 Power in From Relay 1's Wire 85
              Wire 87A Ground

              How much current do your LED's Draw? Maybe you don't even need a really heavy duty relay. Some at Radio Shack are good for 10A.

              Lots of ways to skin this cat.

              Comment


              • #8
                Why not just connect the LED+ to IGN +12V, and connect LED- to headlight +12V.
                That's assuming halogen or similar headlight bulbs - the LEDs will ground thru the bulbs when they are off.
                Use one diode each for hi and low beams - ie, LED- into 2 diodes; diode-band towards hibeam +12V & lobeam +12V. If LEDs are under 1A, any 1N400x diode will do.


                Originally posted by redheadedrod View Post
                With standard automotive relays a Diode is not necessary since it is already included in the package.
                No - very few relays come with inbuilt diodes. (My preference is plain relays with no inbuilt resistors or diodes. I then add diodes externally if required.)

                Comment


                • #9
                  Couldn't you just use one relay, and not connect one of the pins?




                  Basically, connect 30 to the ignition, 87a to the LEDs, 85 to the headlights, 86 to ground, and then just not connect 87 to anything? When the coil is activated, it should flip to 87, but since the LEDs aren't connected, they should turn off. Am I missing something?

                  Comment


                  • #10
                    That should work noting that that if using the relay that redheadedrod described, you'd blow the fuse or the internal diode. (IE - hence the convention that 86 is more +ve than 85).

                    But as I described, a relay probably isn't necessary.

                    Comment


                    • #11
                      Tbird has never responded with the Full Load Amps of his LED's. We are assuming that the current draw is low enough to be drawn straight from the ignition source. In my scenario I suggested a constant +12VDC fused source (possibly battery). Tbird has also never set any other parameters, easiest, cheapest, fastest, least number of parts etc. . Nor has Tbird responded with any clue as to what his preferences are, Ignition to power LED's, fused battery source to power LED's. Everyone who has responded has had some great ideas, All the suggestions I have seen here will work. It's all up to Tbird, or any other user to do a little research, decide what the parameters are that they want to try to achieve, and just do it. Just be safe, use fuses, make solid wiring connections (ie solder) so as to avoid problems later. And use a neat wrap of electrical tape to insulate your connections, or heat shrink them. Harbor Freight sells a cheap little voltmeter that I highly recommend to everyone, just so that you can tell if you have power or not, check for continunity, etc. I think I bought one on sale for $2.99.

                      Lots of different ways to do this.

                      Comment


                      • #12
                        Totally agreed. And therein the problem with under-specification. (We repliers provide various possibilities & the OP must eliminate & decide.)

                        My experience is that LEDs consume less than relays (relay coils are usually 50-200mA) and that IGN and light circuits have the capacity to handle added LEDs.

                        For LEDs, generally it's only when novel combinational switching/control is required that relays etc are required.
                        And whilst I'd generally suggest relays rather than "power" diodes for other loads, where LEDs consume under 1A I reckon 1N400x diodes are fine to power the LEDs directly for simple combinational control (ie, omit the relay since diode current and voltage drop is not an issue).


                        Of course the main thrust of my original reply was to use phantom or virtual (or whatever the heck they should be called) grounds to control the load. EG - LED+ to IGN +12V, and LED- to the beam +12V (or hi & lo beam +12V) so that they are off when beams are on ad on when IGN is on & beams off.
                        That assumes the beam or hi/lo bulb resistance to GND is much lower than the LEDs.
                        The same is done for flasher beepers - eg, motorcycles - just a buzzer between left & right flasher +12V feeds (assuming flashers are light bulbs).

                        Comment


                        • #13
                          Thanks for all the replies. These are the LED strips I got.. I highly doubt they draw much current.

                          http://www.amazon.com/gp/product/B00...ls_o03_s00_i00

                          As for what I want. I want them to act like DRLs (daytime running lights). They should come on when the vehicle is on and go off when the headlights come on (and the vehicle is on)..

                          I have numerous relays laying around as I used to do remote starter installs so I have plenty (with the harnesses) to use. I want to do this the easiest way possible with the least amount of wires.. But I will do what it takes..

                          My issue now is I can't effing find an ignition (or an accessory wire for that matter) under the hood. I have a 2008 Nissan Altima Sedan..

                          Yes, I have a multimeter as well..

                          Thanks
                          Current Vehicle: 2007 Dodge Nitro

                          Second Vehicle: Sold it :( 2005 Dodge Ram 1500 Quad Cab

                          First Vehicle: 2003 Ford Ranger

                          Comment


                          • #14
                            Originally posted by tbird2340 View Post
                            Thanks for all the replies. These are the LED strips I got.. I highly doubt they draw much current.

                            http://www.amazon.com/gp/product/B00...ls_o03_s00_i00

                            As for what I want. I want them to act like DRLs (daytime running lights). They should come on when the vehicle is on and go off when the headlights come on (and the vehicle is on)..

                            I have numerous relays laying around as I used to do remote starter installs so I have plenty (with the harnesses) to use. I want to do this the easiest way possible with the least amount of wires.. But I will do what it takes..

                            My issue now is I can't effing find an ignition (or an accessory wire for that matter) under the hood. I have a 2008 Nissan Altima Sedan..

                            Yes, I have a multimeter as well..

                            Thanks
                            It should be easy enough to find one in the fuse box. I had plenty of fuses that got power on ignition. Pick one that will allow you to use one of those add-a-fuse things (I think those have some sort of maximum amperage rating you can put through them).

                            Comment


                            • #15
                              I looked and probed for like 15 minutes tonight.. I guess I'll look again tomorrow..
                              Current Vehicle: 2007 Dodge Nitro

                              Second Vehicle: Sold it :( 2005 Dodge Ram 1500 Quad Cab

                              First Vehicle: 2003 Ford Ranger

                              Comment

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