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    #16
    Indeed.

    Oh, I forgot to mention that I'm also using a diode across the coil of the relay to prevent reverse current spikes upon coil deactivation. This way the current produced by the collapsing magnetic field is dissipated as heat through the coil instead of potentially causing wear on the OEM electrical sysytem.

    Comment


      #17
      That's a great idea. I never thought of doing that. Am I correct in assuming that the cathode gets connected to +12V since we're trying to prevent reverse current spikes? Also, would say a 1N4001 silicon diode be appropriate or would a Germanium diode such as a 1N4148 be better?
      02 DX Millenium Red - The Penultimate Driving Machine
      MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
      MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
      Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
      MP3 Shifter, Knob and Aluminum Pedal Set
      Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
      Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
      Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
      Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
      Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
      Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
      Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
      Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

      Comment


        #18
        Yes, cathode is connected to +12V. Almost everyone uses 1N4001 diodes. I decided to get a beefier diode, but I can't tell you the 1N equivalent because I got it at Fry's Electronics and the supplier was NTE (part number of the sort NTE123). The diode's current rating was my main concern. 50 volts should be enough, but I decided that the current rating should be around 5 amps. Again, over-engineering on my side, but better be safe than sorry.

        Comment


          #19
          Thanks for the idea and the advice. You are one of the Forum electron kings.
          02 DX Millenium Red - The Penultimate Driving Machine
          MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
          MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
          Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
          MP3 Shifter, Knob and Aluminum Pedal Set
          Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
          Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
          Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
          Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
          Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
          Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
          Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
          Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

          Comment


            #20
            regrounding the the engine and the two upper ground points behind the headlights is the easiest way to kill two birds with one stone
            you'll get better starts and brighter lights..

            run all wires to one grounding point and that point to the battery
            eat me

            Comment


              #21
              Originally posted by Intruder
              I have reached the conclusion that it may be overkill. Especially because the HID ballasts are rated at only 35W. But at least I am sure they have all the juice they will ever need.
              Daniel Stern recommends 12 or even 10 gauge wiring in his write-up about upgrading harnesses, but he is referring to a standard halogen system, so the power draw would be higher. I imagine it wouldn't be an issue for your application, but it's probably worth keeping in mind for those of us without HIDs.

              Originally posted by Intruder
              Oh, I forgot to mention that I'm also using a diode across the coil of the relay to prevent reverse current spikes upon coil deactivation. This way the current produced by the collapsing magnetic field is dissipated as heat through the coil instead of potentially causing wear on the OEM electrical sysytem.
              Would this be important using a halogen system? I know the HIDs spike when they're turned on, but what about when they're turned off? Do both systems work the same?

              Comment


                #22
                The diode comes into play whenever you're using a coil relay. So, yes, it applies in both halogen and HID cases because the spike I was referring to is caused by the coil of the relay, not the load in the system (be it a ballast or a halogen bulb).

                A HID system spikes in a different way, but that's a long story, and totally unrelated to the relay. To make it short though, the ballast pumps out kilovolts during start-up to create the arc in the bulb and ignite the gases. During that "striking" period the ballast can draw up to 15 amps of current from the electrical system and this is why I decided to use a relay harness instead of relying on my OEM wiring.

                Basic understanding of electricity and some simple calculations showed that a halogen bulb's nominal current draw is about 4 amps and we already know that it does not spike on start-up. (formula used: I = P(W)/V(V); I(A) = 55W/14V = ~4 A).

                On the other hand we have a HID ballast which has been bench-tested and observed to draw up to 16 amps at start-up. Current draw drops to about 4 amps at steady state but that doesn't happen for at least 20 seconds and during that time I would be subjecting the OEM wiring to current levels higher than normal. And that is why it's a good idea to use a relay harness.

                So in that case (back on topic) the OEM harness will only be powering the relay's coil. When current flows through a coil it creates a magnetic field. When the flow of current is stopped (relay coil deactivated when headlight switch is turned off), the magnetic field starts to collapse and induces current in the coil. That current can spike to dangerously high levels and over time may cause parts of the OEM wiring to fail. I was most worried about the headlight switch.

                We connect a diode in parallel with the coil so that it will act as a short when that reverse current occurs. As you probably know, current follows the path of least resistance and a short has (theoretically) zero resistance. When the diode is forward biased (+ to + and - to -) it allows current to flow freely and acts as a short circuit. This way it prevents that spike current from going back to the headlight switch. It will instead let that current flow through the coil and dissipate in the form of heat in the matter of ... milli or micro seconds. I hope that makes sense.

                BTW, I've attached a diagram showing how a HID ballast behaves during start-up just so you know I wasn't making up those numbers. Green line is cold start-up, red line is re-start.

                Edit: here's a link to the image instead click
                Last edited by Intruder; 03-31-2006, 12:22 AM.

                Comment


                  #23
                  So a diode creates uni-directional current flow by acting as a short circuit when it's flowing the wrong way?

                  And just to clarify my limited electrical knowledge:
                  When you say the diode is wired in line with the coil on the relay, you're talking about wiring it between the headlight switch in the dash and the switch input (86) pole on the relay, right?

                  Comment


                    #24
                    The diode must be wired in parallel with the coil. That is from terminal 86 to terminal 85. The cathode of the diode must be attached to term 86 (+12V) and the anode of the diode to term 85 (GND). If wired oppositely, the diode will simply conduct between the two terminals and short out the coil.
                    02 DX Millenium Red - The Penultimate Driving Machine
                    MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                    MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                    Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                    MP3 Shifter, Knob and Aluminum Pedal Set
                    Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                    Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                    Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                    Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                    Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                    Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                    Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                    Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                    Comment


                      #25
                      Okay, that's what I was not understanding about the short circuit stuff. I was imagining the diode wired inline with the switching circuit, just to block the backflow of electricity to the dash switch.

                      Comment


                        #26
                        I meant to include a small list of suitable silicon diodes that can be used for this purpose. All of these have axial leads and are available from Mouser Electronics, www.mouser.com

                        1N4001 1A, 50V
                        1N5400 3A, 50V
                        Intruder uses a 5A diode. I couldn't find a listing for a 5A but found one for a 6A.
                        6A05 6A, 50V
                        6A1 6A,100V

                        Bear in mind that the greater the amperage rating, the larger the diode, which might cause a mounting problem if space is limited.

                        Happy Motoring!
                        Last edited by goldstar; 03-11-2010, 03:18 PM.
                        02 DX Millenium Red - The Penultimate Driving Machine
                        MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                        MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                        Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                        MP3 Shifter, Knob and Aluminum Pedal Set
                        Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                        Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                        Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                        Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                        Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                        Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                        Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                        Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                        Comment


                          #27
                          Originally posted by jnorion
                          So a diode creates uni-directional current flow by acting as a short circuit when it's flowing the right way?

                          And just to clarify my limited electrical knowledge:
                          When you say the diode is wired in line with the coil on the relay, you're talking about wiring it between the headlight switch in the dash and the switch input (86) pole on the relay, right?
                          The diode is like a one way street. It lets current flow one way but not the other. Forward bias passes current, reverse bias blocks current (to a point, this is why you have voltage/current ratings). Bias is just a term used to describe how the diode is connected in the circuit.

                          I said the diode is wired in parallel, not inline. Parallel means across the two terminals of the coil as goldstar explained.

                          Comment


                            #28
                            Originally posted by Intruder
                            I said the diode is wired in parallel, not inline. Parallel means across the two terminals of the coil as goldstar explained.
                            Yeah, I figured it out after the second explanation. I went back and reread your first post but skipped over the full description. My bad.

                            Comment


                              #29
                              AWG Variations Versus Voltage Drop

                              SgtRauksauff had mentioned that he uses 70W high beam bulbs in contrast to OEM's 60W spec and wondered if 14 AWG conductors might not be adequate for the increased current draw. Others have also wondered if 12 AWG or even 10 AWG conductors might be a better choice even with the standard 60/55W bulbs in terms of producing noticeably more visible light output.

                              All of the Suvlights heavy duty wiring harnesses that would be suitable for our cars utilize 14 AWG conductors. However, based on the current draw of our headlight bulbs, and the conductor length required, I believe that 14 AWG is more than adequate for the purpose, and that the use of 12 or 10 AWG would essentially be overkill. I base that conclusion on the following discussion.

                              I measured the conductor length of my harness, from battery + terminal to the headlight plugs. As the harness is already installed it was not possible to make an exact measurement. The result was 4'6" (4.5') for the driver's side and 10'4" (10.33') for the passenger side. Consider these lengths approximate but close enough for illustrative purposes.

                              I then looked at the resistance figures in ohms/1000' for 14, 12, and 10 AWG conductors taken from the Brown and Sharpe Wire Gauge tables, and added my own calculations for my harness conductor lengths. The results appear in the table below.

                              Table 1: Resistance as a Function of Length
                              AWG _____ Ohms/1000' _____ Ohms/4.5' _____ Ohms/10.33'
                              14 __________ 2.525 ____________ .0114 ___________ .0261
                              12 __________ 1.588 ____________ .0071 ___________ .0164
                              10 ___________ .9989 ___________ .0045 ___________ .0103

                              Now I was ready to calculate the wattage output of a headlight bulb as a function of the three conductor sizes considering only the high beam for the bulb on the driver's side (4.5' conductor). This will be done for both a 60W and a 70W (as used by Sarge) nominally rated bulb at 12V. Remember at the running alternator voltage of 14V+, the wattage output of a 12V nominally rated bulb is considerably higher. I may provide additional calculations for the passenger side bulb, and the running voltage, at a later point if I can find the time.

                              Considering a headlight circuit, the bulb filament is the electrical load and the conductor acts as a resistance in series with the load. In a series circuit, the current is everywhere the same but the voltage varies as a function of the IR drop of the various resistances. Thus, the voltage at the bulb filament will be less than the nominal 12V due to the IR (voltage) drop across the length of the conductor. Since W = E x I in a DC circuit, any reduction in voltage (E) at the bulb filament will result in a reduction in wattage. But by how much?

                              Calculating Wattage Output as a Function of Conductor Size
                              The arithmetic is actually pretty simple. Start with the nominal ratings for, say, a 60W bulb. From Ohm's Law, at 12V, the filament is rated at 5A in order to produce 60W. Assuming a 14 AWG conductor, multiply the ohms per 4.5' taken from Table 1 above, by 5A, (.0114 x 5) to obtain the IR drop which = .057V. Subtract this voltage drop from the nominal 12V making the total voltage at the bulb 11.943V. Finally, multiply this last figure by 5A for a total output wattage of 59.715. For other conductor sizes, use the appropriate ohms per unit length resistance.

                              The proceedure for making the same calculations with a 70W bulb is identical except that here the current rating with a nominal 12V bulb will be 5.833A (12 x 5.833 = ~ 70) rather than 5A. The table below illustrates these relationships.

                              Table 2a: 60W Bulb Nominal Output at 12V, 4.5' Conductor Length
                              AWG _____ IR Drop _____ Bulb V _____ Output W
                              14 ________ .057 ________ 11.943 _______ 59.715
                              12 ________ .0355 _______ 11.965 _______ 59.823
                              10 ________ .0225 _______ 11.978 _______ 59.888

                              Table 2b: 70W Bulb Nominal Output at 12V, 4.5' Conductor Length
                              AWG _____ IR Drop _____ Bulb V _____ Output W
                              14 ________ .0665 _______ 11.934 _______ 69.608
                              12 ________ .0414 _______ 11.959 _______ 69.755
                              10 ________ .0262 _______ 11.974 _______ 69.843

                              As can be seen, at a conductor length of 4.5', variation in AWG from 14 to 10 makes no discernable difference in output wattage.

                              Happy Motoring!
                              Last edited by goldstar; 03-11-2010, 03:58 PM.
                              02 DX Millenium Red - The Penultimate Driving Machine
                              MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                              MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                              Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                              MP3 Shifter, Knob and Aluminum Pedal Set
                              Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                              Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                              Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                              Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                              Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                              Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                              Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                              Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                              Comment


                                #30
                                As this applies to the BJ, I moved it from Do It yourself! How To......... because it was buried there and difficult to access. From PMs I received, it was apparent that some of our members either didn't know of its existence or couldn't locate it.

                                Happy Motoring!
                                02 DX Millenium Red - The Penultimate Driving Machine
                                MP3 Strut Tower Bar kit; Cusco Front Lower Arm Tie Bar
                                MSP Springs, Struts, Stabilizer Bars, Trailing Links, #3 Engine Mount
                                Kartboy Stabilizer Bar Bushings; Nyloil Shifter Bushings; Red Line MT-90 Gear Oil
                                MP3 Shifter, Knob and Aluminum Pedal Set
                                Suvlights HD Wiring Harness; Osram Night Breaker H4 Bulbs; Exide Edge AGM Battery
                                Summer: 5Zigen FN01R-C 16 x 7" Wheels; Yoko S.drive 205/45-16s
                                Winter: Enkei OR52 16 x 7" Wheels; Falken Ziex ZE-912 205/45-16s
                                Modified OEM Air Intake; Racing Beat Exhaust System; Techna-Fit SS Clutch Line
                                Denso SKJ16CR-L11 Extended Tip Spark Plugs; Magnecor Wires
                                Power Slot Front Brake Rotors; Techna-Fit SS Brake Lines; Hawk HPS Pads
                                Red Line Synthetic Engine Oil; C/S Aluminum Oil Cap
                                Cyberdyne Digital Gauges: Tach; Ambient Air Temp; Voltmeter

                                Comment

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