Where do the leads of a zener diode connect to in a DC system?

I have a light in my car that takes two incandescent type light bulbs, but when I use both sockets, the bulbs are broken open and some of the glass is melted in a couple weeks. I've bought plug and play LED lights that have multiple LEDs (with a resistor on both the cathode and anode) and just plug into the sockets, and I used both sockets, they lasted about two months. And since I had only one spare bulb in my center console, I plugged it in, and its been working for over a year (this is where I found out that using both sockets made the lights fail). I'm guessing that the when the engine starts, it sends a surge to the light.

So I decided, that I'll just make my own light using LEDs, I have everything resistors LEDs and wire, but I'm unsure where to connect a zener diode/s to the LED array (or if a zener diode would even protect the array). I've looked on the net, but some say to solder inline and some say it needs to connect to the ground, and I cant tell which is right for my case.

I've included the output of the LED calculator and the specs. below.

    Source:                     12V
    Diode Forward:       1.8
    Diode Amps.:          20mA
    Number in Series: 24

   Solution 0: 6 x 4 array uses 24 LEDs exactly
+----|>|----|>|----|>|----|>|----|>|----|>|---///----+ R = 68 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---///----+ R = 68 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---///----+ R = 68 ohms
+----|>|----|>|----|>|----|>|----|>|----|>|---///----+ R = 68 ohms

The wizard says: In solution 0:
*each 68 ohm resistor dissipates 27.2 mW
*the wizard thinks ¼W resistors are fine for your application
*together, all resistors dissipate 108.8 mW together,
*the diodes dissipate 864 mW total power dissipated by the array is 972.8 mW
*the array draws current of 80 mA from the source.

lemonie7 years ago
framistan7 years ago
Be sure to check your car for proper voltage when engine is RUNNING.  I had a friend whose car kept burning out radios and headlights.  he took it to the dealer, and they replaced headlights and radio... but neglected finding the TRUE reason things were burning out so much.  I put my voltmeter on his battery BEFORE starting the car and had something like 12.8 volts or 13.1... something low like that... then he STARTED the car and his voltage went to about 14 or 15 volts !!!  rather high.  So he took the car back and they found his alternaters REGULATOR was FULL ON.  instead of regulating the voltage down to about 13 volts,  it was pumping out FULL POWER at all times....c ausing various items in the car to burn out.   If you dont feel confident using a VOLTMETER, you can go to any auto parts place and buy a little LED voltmeter that plugs into the cigarette lighter.  It will tell you if the voltage is too low or too high when engine is running or off.  they only cost about 7 or 8 bucks.  Hope that helps you.
LuciferTengu (author)  framistan7 years ago
Yeah I got my alternator replaced awhile ago (it started squeaking), and can't remember if the store bought LEDs burnt out before or after. But yeah, I should get around to checking the voltages (engine off and on) before I get the the zener diode.