zener vs regulator. help

i am having trouble getting started. i would like to start off with using a static regulated power i have driving or rail voltage of 12-15vdc. i dont really care what voltage i use to drive my circuit with but it needs to be the same all the time. i have zeners and i also have a LM317 voltage regulator. i was thinking 10 or 12vdc would work

the zener i have tried using a trim pot from 0-1k ohm to try to figure out how this works and i can only get around 4v and it doesnt seem very adjustable. and it responds very unpredictably

am i doing something wrong or should i switch to the lm317 as a regulator]

You certainly got it wrong! The Zener must be connected between ground and the resistor from +12...+15 V to its other end (where you can get your 4V regulated) must be calculated from the DC current you want to draw to your load. Allow the Zener to take some 50-100 mA to regulate. Calculate also the power loss for your resistor.

Why people never read the basics before starting to make a circuit??!!

A LM317T can be used instead the Zener and it also regulates better. It also replaces the dropping resistor but needs two more resistors to set the output voltage. Read the data sheet for details!!

The anode of the Zener diode (the side without the "bar") must be connected to ground, which means the cathode is the point where you expect your Zener voltage to be. The Zener voltage is not a "promised" voltage--you must design it for the amount of current in your circuit, and even then you must be sure that this current isn't varying widely, or else you'll have a fluctuating voltage. I highly suggest using a linear regulator like the LM317 (or a specific fixed-voltage regulator) if you need a good regulated voltage

With linear regulators like the LM317, you don't have to worry about fluctuating currents, and you have to do less work to "design it into your circuit." With the LM317 (and other 3-terminal linear regulators), you must make sure that the current that the LM317 can output is greater than what your circuit will require. Also, make sure that you have the correct input/output capacitors for energy storage/ripple reduction. Here's a link to a good application note:

**broken link removed**

Page 22 will likely be helpful to you.