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Help understanding a basic electrical circuit

  • 04-03-2013 4:42pm
    #1
    sebastianlieken
    Registered Users, Registered Users 2 Posts: 1,778 ✭✭✭


    Sorry if this is wrong forum, I couldn't find an electrical / electronic forum.

    Anywho, I went about fixing the high level brake light in my car the other day and discovered that it is a long and slender circuit board with the following basic design

    +12V+ -> C1 -> R1 -> R2 -> R3 -> C2 -> (20 x Led's in series) -> -12V-

    what is the purpose of C1 and C2? (capacitors by the way). Through a bit of testing, I found that C2 was faulty, so I just removed it and bypassed it. It works now... But surley that capacitor was there for a reason?!

    thoughts please?


Comments

  • #2
    sebastianlieken
    Registered Users, Registered Users 2 Posts: 1,778 ✭✭✭sebastianlieken


    oooooh.... actually I just realised something.

    That C2 isn't a capacitor at all. it's a Protection diode.

    Now to figure out whether or not I really need that protection diode in the circuit....


  • #3
    nogoodnamesleft
    Registered Users, Registered Users 2 Posts: 1,031 ✭✭✭nogoodnamesleft


    It would be advisable to use a multimeter set to continuity to determine what component is actually blown on the circuit rather than guessing.

    Something has obviously blown and failed open circuit, identify the problem component, get a replacement with the same value be it ohms, farads or what ever and replace.

    Capacitors if they are actually capacitors (from your description) could be smoothing capacitors for feeding the leds.


  • #4
    longhalloween
    Closed Accounts Posts: 2,207 ✭✭✭longhalloween


    Any chance you could take a picture?

    Your 12V supply is a battery so you won't find capacitors wired in series. Most likely some sort of a fuse or diode.

    If the capacitors are wired in parallel then it may be a protection against variances in voltage.


  • #5
    ciaranmac
    Registered Users, Registered Users 2 Posts: 495 ✭✭ciaranmac


    Doesn't make any sense to have a Cap in series with LEDs. It would make them switch off when it maxes out.

    If the cap C1 is electrolytic and in parallel with the LEDs, then the diode could be in series with it to protect it from reverse polarity. Electrolytic caps (look like tiny beer tins) can be destroyed by a reverse voltage.

    Also having multiple resistors in series is usually only needed to get a very precise value. Generally speaking LEDs will work with a fairly broad tolerance of values for their current-limiting resistor, so you would only need one. Are they all the same value? (same stripe pattern)

    Are you suuuure the components are all in series? I'd say have another look at that circuit or take a picture like longhalloween suggested.


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