🔴 Electronics For Beginners - No.12 - Linear Power Supplies - No.972

[@davidv1289]

I am enjoying this series - lots of good information. Have you considered using a breadboard for your demonstrations - the relationship of the components would be a bit clearer (though a bit more fiddly to set up)

[@TheEmbeddedHobbyist]

With the zener in the 0V lead you are hoping that the Quiescent current is enough to push the zener past it's knee voltage, or you will lose regulation a bit. I also like to use them as constant current supplies where you just put a resistor between the output and the 0V input. The regulator will try and maintain its set output voltage across the resistor (don't connect to 0V pin to 0V for this). So output voltage/ resistance = constant current value. Used to use this a lot for charging nicads in the old days.

[@IanScottJohnston]

If there's not enough quiescent current then a resistor from the Reg output to the Reg 0V connection helps. Worthless tidbit that won't change anyones life: Think of a fixed 7805 Reg as an LM317 adj. Reg with both the resistors inside the package setting the output to 5Vdc.

[@TheEmbeddedHobbyist]

​@@IanScottJohnston Ian you are too modest, i will now always see a LM317 peeking out of the plastic case now that you have implanted that image.

[@IanScottJohnston]

@@TheEmbeddedHobbyist Actually, if you look at any datasheet for a 78xx or 79xx you'll see the resistors....🙂

[@stevenbliss989]

Sorry to nitpick, but I expected (at 16:30) for R1 to be at the emitter of the 2N3055. Or is there something about the LM317 that prevents this?

[@mikeepeck]

Never knew that, thanks!

[@Daveyk021]

As far as I have always know, a transformer output is shown in RMS, NOT P-P. therefor, a 20v transformer will create about 26.9vDC