help understanding power regulation

Discussion in 'General Electronics Chat' started by scampo77, Apr 10, 2012.

  1. scampo77

    Thread Starter New Member

    Jun 24, 2011
    i was told "first step start with a zener" this is so i have a more stable circuit. so i usually start with a 12v zener, this is what i type into ebay or ask for at the parts store and this is what i get, a "12v zener". i never really questioned what i was getting till now. i was digging in my parts box and i came across a 1N5242B. when i looked up the data sheet it says it is an adjustable zener from 1v-200v. how can a regulated power device like a zener be adjustable?

    also i have seen other power regulators usually in a TO-220 case are these adjustable too or are they "locked" like a zener?

    any light shed on this would help me out a lot
  2. paulktreg

    AAC Fanatic!

    Jun 2, 2008
    The 1N5242B is a 12V Zener Diode. for the TO-220 cased devices do you mean voltage regulators? You can get many types of fixed voltage regulators like the 7805 (+5V), 7812 (+12V), these are fixed and devices like the LM317K that are variable and require external resistors to set the output voltage.
  3. scampo77

    Thread Starter New Member

    Jun 24, 2011
    the LM317 is the exact one i was talking about. i work mostly on 12v car amlifiers and there is usually a lm317 and a lm337. if they are in fact adjustable, does that mean i can use them for 1-50v of regulation? how do you set the voltage output level?

    this is what is on the data sheet for the 1n5242b, am i miss reading this?

    "Wide spectrum from 2.7 V through 36 V of zener voltage provide flexible application"
  4. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    Yes. They are advertising their RANGE of zener diodes, covering a span of 2.7V thru 36V. There are other 'series' as well covering similar ranges but with slight differences like max wattage.
  5. scampo77

    Thread Starter New Member

    Jun 24, 2011
    so every zener diode has only 1 specific output voltage?
  6. praondevou

    AAC Fanatic!

    Jul 9, 2011

    Something that could act as an adjustable zener diode (even if it's not really one) is the TL431 voltage reference.
  7. panic mode

    Senior Member

    Oct 10, 2011
    no, 1-50V is too wide range for LM317. also while LM317 can be used to make adjustable voltage regulator, it does not mean that it should be used over it's entire span all the time. the problem is that voltage is only one of parameters. others are current and dissipated power. the greater the difference in voltage between input and output, the greater the voltage drop across LM317. Power is P=V*I

    If both voltage and current are large, power becomes very large. this is power that is wasted as heat and needs to be taken away from regulator, otherwise it will burn.

    The advantage of LM317 over fixed regulators (like 7805, 7812 etc.) is that by using two resistors one can set output voltage to anything (within limits). This also means using (stocking) one part instead of variety. It also means ability to fine adjust output if needed (you just cannot simply dial 7805 to some voltage that is close to 5V but not really 5V).