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Basic Electrical Question

Discussion in 'ECU's, Electronics, and Tuning' started by humblegumbo, Jul 27, 2007.

  1. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    I have purchased a set of aftermarket fog lights w/ an install kit. The kit instructs the user to wire a dedicated switch to run the lights.

    I would prefer not to do this.

    What I want to do is to have them turn on when I run my parking lights and then get brighter when I run headlights. So, if I take the power source from the running lights to the fog lights, that will work for that portion.

    If I run another lead from the headlights to the same terminal on the fog lights, will the extra voltage make them brighter. I assume it will. But, will that voltage also run back to the parking lights circuit? And will parking lights voltage then also flow to headlights? I do NOT want either of those events to occur.

    I don't want to burn anything out, for sure.

    Thanks for any help.
     
  2. OLD_HATCH

    OLD_HATCH New Member

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    I dont think that will work.

    parking and headlights both use 12 volts so you would get the same brightness.

    to run them with the parking lights you should just be able to tap into the driving light positive to the wire harness kit of the fogs. you might be able to get creative with a diodes/resistors/relays to do what you re trying to do.
     
  3. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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    The suggestion of using a relay with a resistor in series with the fog lights so when the parking lights are on they are dimmer and then brighter when the headlamps come on is a good idea, keep in mind the resistance of the light bulb changes as the filament gets hotter, so initially if you manage to wire the fog like your after the lights will look slightly dimmer until the filament gets up to maximum operating temperature. if it has a dual filament light bulb then yes you could tap into the parking light feed for the low beam, and tap into the headlight feed for the high beam. Keep in mind everything in car is wired in parallel so each circuit can draw current independent of one another but all circuits are powered by 12Vdc.
     
    Last edited: Jul 28, 2007
  4. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    Okay, thanks.

    I understand that the whole system is powered by 12vDC, but what about amps? If I combine the let's say 15 amps from the parking lights with the say 30 from headlights will that make a difference?

    I'm almost positive that this is a single filament bulb I am dealing with, though if I can find a dual bulb that fits I'm not opposed to swapping it.

    But it sounds like wiring two power sources into the single filament is not going to work. :(

    Another option is to source some junkyard fogs and wire them in. Then I could return the cheapo aftermarkets I got. Hmmm...it's going to be a beautiful day for the junkyard. :cool:
     
  5. Kyle21nluvnit

    Kyle21nluvnit New Member

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    amperage is determined by the voltage and resistance of the circuit. Crosssing circuits will deffinatly damage stuff. If you have 12V and 6ohm of resistance in the circuit is will be a 2A circuit, if you have 12v and 4ohm of resistance it will push 3A and so on and so on. Using a resistor as was said before is really the only way to do this right. Thats a very rough paintshop drawing lol but you need to find 12v power from your running lights and regular lights. get a resistor block with 3 pins one with 0ohms one with the same ohm rating as your fog lights and one pin open inside. run you running light to the pin the the same resistance as your lights, run the headlight power to the pin with 0ohm resistance then connect the outputs of both to your foglights and ground after that. When you have the running lights on the resistor will make your lights dimmer and when you turn on the main lights there wont be any resistance so they will be normal. good luck and have fun.
     

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  6. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    Okay. Thanks.

    I think I understand at least the basics of what you're saying. Electrical stuff just blows right over my head most of the time. That resistor block is a pretty trick idea though.
    Sweet.

    Edit:

    Well, upon further research, I have no idea where to find one of these three pin resistor blocks. It seems that it would be easier (for me anyway) to set this up with either a dual filament bulb or two single filaments. Either way, when I hit high beams the fogs will rerun to running light output. I haven't decided if I want this or not.
     
    Last edited: Jul 30, 2007
  7. CRX-YEM

    CRX-YEM Super Moderator Moderator VIP

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    I would highly suggest against using a 3 ohm resistor to carry a 3 amp load unless its a wire-wound power resistor. Most resistors are rated at 1/4 watt and with a 12volt source and a current of 3 amps you're looking at about 36watts of power dissipation, Instead of using a series resistor make yourself a voltage divider or use a voltage regulator.
     
  8. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    Huh?

    Sorry, that's all gibberish to me.

    I've rethought my options and have pretty much decided to run the power from the running lights through the kit's switch and then to the lights. That way, I can control the fogs, but they won't run unless the running lights are on.

    If I ran them straight from the battery, then I'd be way more likely to forget them and drain the battery.
     
  9. Kyle21nluvnit

    Kyle21nluvnit New Member

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    if your going that route I would pull my power from the fuse box and find where your switched ignition power comes in. Build your own circuit with a fuse from the switched power circuit(before the fuse on that circuit). then you will have power to your fog lights and switch with the ignition on. Cutting into your light circuit will affect the current of that circuit. I know my picture was very crude but it was just to give you an idea. If you want I will draw you a real wiring daigram of where you should hook everything up. just message me.
     
  10. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Please also dont use my sketch for a functional diagram I dont know your lights so I just put values in there for reference purpose only 3ohm is not what I would use either. This was only to show you a stepped resistance setup. For a real world example look at a diagram for a blower motor regulator this is almost the same thing(and might work for your purpose).
     
  11. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    Don't worry about me blaming anybody else for my electrical short-comings.

    My main goal in all of this is to have the fogs operate w/ the OE light switch on the steering column. Ideally, I could leave the switch for the fogs in the 'on' position, but they wouldn't light up until I turned on the running/parking lights. However, there may be occasion where I'd want to have headlights running w/o fogs.

    I'll see if I can come up w/ my own crude drawing of what I think I want.

    Edit:

    okay, threw this pic together pretty quick. keep in mind that although I did not bother to draw in the rear running lights, I have set them all up w/ LED bulbs, so they don't draw anywhere near the amount of power that regular bulbs would.

    Then again, I'm not sure how watts translate between volts and amps....
     

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    Last edited: Aug 1, 2007
  12. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Ok the important things in electrical are Amps(amount of energy), voltage(push of energy, or electrical pressure) and Ohms which is the resistance of the circuit. If you know voltage is 12v and you know that your resistance is 4ohm for example your amperage would be 3amps the formula is Amp= Voltage/Resistance, Voltage = AmperageXResistance, Resistance = Voltage/Amperage, Watts = Voltage X Amperage. Watts are a measurement of energy usage over time. Hope this helps and make sure you take the resistance of the whole circuit not just a single load. If you need anymore info just let me know.
     
  13. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Also the amperage used depends on the resistance i.e. if you have 3ohm total resistance with two 1.5 ohm loads on a 12v circuit you will have 4 amps on the circuit and each load would use 2 amps.
     
  14. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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  15. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    All these great posts involving resistors and ohms scared my too much. So, what I ended up with are the fogs running straight off the parking lights. No problems at all so far.

    They are bright as hell, though. Way brighter than I was expecting, in fact. I've got people moving out of my way on the freeway now. Bitchin'. So, maybe I'll wire in a switch to avoid trouble w/ Johnny Law.

    Other fun electrical mods in the works include a "stealth switch" to disable all exterior lights (especially brake) except for the fogs and a "back-off switch" to independantly operate reverse lights w/o shifting into reverse.

    By next weekend I hope to have all information and parts to step down voltage from 12vDC to 5 and run the voice box from a R2D2 toy in place of seatbelt/door buzzer.
     
  16. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Sounds like a lot of fun doing those conversions. None of them should be especially difficult but watch out for the "stealth switch". I had a friend who had one and got caught with it and got landed in jail for 90 days and a $2,500 fine for having it equipped and using it on the road. I dont know your local laws but be very careful doing something like that its very illegal. he got out for good behavior after 30 days but he removed his and never thought about puting it back in :).
     
  17. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    Holy hell! 90 days? F that...not worth it.

    For the R2 buzzer conversion, I picked up a universal car charger that has adjustable voltage output. I'll crack it open, set it to 5 wire it up, and solder the circuit on the toy closed. I also found a small amplifier kit at Fry's. So I'll put that together and hook it up to R2's output.

    I think this is the one mod that I'm really looking forward to pulling off the most. I've never seen anybody do anything like this before. It very much personalizes the car w/o changing the appearance at all.

    Now all I have to do is find that damn buzzer...........
     
  18. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Way easier than breaking open a voltage regulator would be to get a 5v zener diode and run it on a parallel circuit, in lamens terms lol. Setup your buzzer completely normal then before any loads or anything on the circuit make a branch and put a 5v zener diode on that circuit with its own ground. The zener diode will make it so the other part of the circuit is automatically on 5V. Just get an auto quality one. Good luck
     
  19. Kyle21nluvnit

    Kyle21nluvnit New Member

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    Owww I miss fry's so much they dont have them around here. you in the houston area?
     
  20. humblegumbo

    humblegumbo 1595cc's of Mad Fury

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    I'd never been before (Fry's) and I spent at least an hour lost in a daze there *after* I foun the mini amp. Place is ridiculously huge. Oh, I'm more in the san diego area.

    See...you start talking about parallel branches and zener diodes and you lost me. Sorry. I'm sticking w/ what I know. I already broke open one of these the other day for another hack job & it was super easy.
     
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