Linear Regulator Amplifier Experiments

[Joster]

Hi All,

Check out the vid if you like! any tips would be excellent

https://www.youtube.com/watch?v=0MNZ...=youtube_gdata

Cheers,

Joe

[Tom C]

just watched,

you said I am only getting the cap to charge to 16 volts.. then you said I have 16 volts on the power supply. why would you expect more from the cap then you are inputing? or are you just wondering why you don't have 16 on the output?

Tom C

[Lman]

Tom C,

He does not mention the voltage on the supply. The cap charges to 16V, and 16V into the regulator is what he said. I am assuming he is supplying the SS oscillator with 12V.

Joster,

What about the Beta Multiplier ? What are the resistor and the zener doing right now? As far as I got it the resistor and zener must be a reference point for the multiplier.

Regards
Lman

[Tom C]

at 1:22 he says the voltage I have going into the regulator is 16 ............... at 1:08 he says the cap is only charging to 16 volt. when he says this he is measuring the input voltage to the cap at the diodes. I am trying to understand if he thinks there should be more at the input.

and yes there should be a Darlington pair in there.

Tom C

[Joster]

Hi Tom C and Lman,

Sorry for the confusion here. I am wondering why the cap is only charging to 16V becuase it is connected to the output of the ss sg which should charge to cap up and up and up which is what it does when I disconnect the rest of the circuit and just leave the diodes and cap across the ss sg output.

My understanding is the the two 15V series zener diodes will control the cap voltage and keep it at 30V. That's why I'm not sure why I am only seeing 16V thereacross the cap.

Yes the ss sg is powered by a 4.2A 12VDC Supply that plugs into mains power and draws 17W.

As far as the resistor and zeners all I know is the total voltage across them is 16V. There is 1, 510 Ohm and 2 15V zener diodes in series and then all that is in parralal across the filter cap. Again, I would think this shold be somewhere around 30V becuase the cap is going to want to keep charging up from the output of the ss sg and the zeners will clamp that down to 30V??

I'm not really sure about the beta multiplier other than there is one inside the lm317 but only good to 1.5A. At this point it would be great to get it working even at that amperage.

It would seem that what John describes in DVD 37 is basically what is in the lm317 but his circuit can handle alot more current, has an adjustable battery float point and indicator leds. Also, I still am not sure how this "DC amp" plays in. Is that "direct-coupled" or "direct current amp"??

I have a long way to go to get this circuit mastered but hey I was right here 6 months ago trying to figure out the cap dump comparator circuit and now have that completely figured out.

Any tips would be excellent!

[Tom C]

I was a little confused about zener diodes in series and came across this page:

http://www.electronics-tutorials.com/basics/diodes.htm about half way down it talks about series zeners.

what is the voltage reading after the first and second zener?

Tom C

[Joster]

good point..that doc shows series zener's but doesn't explain what happens when they are in series....is 15V + 15V really 30V??? I will measure it when I get home in about 1.5 hrs....do you happen to have any hints about the beta multiplier??

i was thinking i am asking alot of the lm317 as the output impedance into the battery looks like a short to the output side of the 317 right??

[Tom C]

the beta multiplier is not in the LM it is a separate darlington pair into the regulator
I do not know what the IC is
Tom

[Lman]

Tom C,

In post #2 you have quoted Joster and mentioned the power supply. I thought you misquoted him maybe since he showed the bench power supply but did not mention the voltage on it. Or I got something wrong ??
My point was that with 12v power supply he would have been able to keep the cap charged at higher voltage if the circuit was correct.

Here is a great read and detailed explanation about the zener and zeners in series :
http://www.electronics-tutorials.ws/diode/diode_7.html
That site is very helpful.

Joster,

You said it yourself - if you disconnect the rest of the circuit the cap would charge higher. Which means ... something is drawing power from it.
Right now you have the LM317 connected like it is supposed to be used as a conventional voltage regulator. The diode from the SS SG feeds both the cap and the regulator so the cap is just as a smoothing filtering cap to the regulator. I can't clearly see on the video on which pin of LM317 you have the resistor and potentiometer connected.

When using zener as a regulator or a reference the regulated point is between the resistor and the zener. Two 15V in series will give you 30V, but the resistor must be in series with the load. Anyway zener regulator is recommended for small loads in the range of a few milliamps not to pass 1.5 A. The way you have them in your circuit - they do not do anything right now. This is why the cap does not charge to 30V as you intended.

I recommended to you to read the 160 Amp solar Tracker thread as John has shared a lot of info there but you either did not read it or did not pay attention reading it ...
I have to repeat John's words. They did not have 3 pin regulators back in time and did them discretely meaning separate components and lots of calculations. Inside LM317 and all the regulators there is a darlington pair but it is not the Beta Multiplier as Tom C noted.
I personally studied the internal schematics of some regulator chips since John mentioned it and learned a lot from that. I was in shock and panic at first but slowly I got to understand most of it.
The first step to understand the the Beta multiplier is to learn the Series-Pass and I will give you a video link and a nice article. And I have passed through a lot of articles which do not explained it well so these are good.

Series-Pass Regulator http://www.youtube.com/watch?v=VDs5SZIFLKk
Series-Pass Article http://www.tpub.com/neets/book7/27k.htm

Than go and read that thread.


LM317 is a little beast - it has built-in current limiting feature and thermal protection as well. Good that you put it on a heatsink otherwise it might have been long gone

Regards
Lman

[Tom C]

he built his solid state SG into the power supply box, and I did not listen really carefully to the first sentence in the video where he says this, so I assumed it was just a plain old power supply. nice video on the series pass!! randy fromm arcade school! he was the go to guy for years in the video game industry.

Tom C

[Lman]

Tom C,
Thanks for clearing that out. I thought it could be me since english is not my native and I am not perfectly confident in my language skills sometimes.
Randy Fromm is a pleasure to watch the way he explains things. That video even hints at how the linear amplifier works.

Regards
Lman

[Lman]

Hey Lman,

My Question is...what exactly does determine (besides the input source) how much current is put to the load. I suppose that's my next area of discovery. I suppose one factor would be the darlington pair and how hard it is driven...I think I may try a pulse width signal to drive the darlington pair.

One other quick thing, when John refers to the "impedance of the battery" is he talking about batt voltage or actual resistance? I'm pretty sure it's actual resistance but I am wondering how he senses that. I assume it would be some kind of sensitive voltage divider op amp circuit that when the impedance rises because of a load being attached to the output (I assume that would happen b/c the impedance of just about any load would be greater than that of a 12V batt) it would divert the current to run the load and float the battery.

Hi Joster,

Consider my answer as my understanding of the things. I might be wrong somewhere.
What determines the amount of current going to the load is namely the amplifier. Let us think for a minute how an audio amplifier works. It sees the impedance of the speaker/s (the load) and adjusts itself. I think that is simple Ohm's Law. If you have an 8 Ohm speaker how the audio amp knows how much current to deliver ? If you have two 8 Ohm speakers in parallel how does the amplifier sees them ?
After John has posted the video with the audio amplifier, the light bulb in my head turned on.
He mentioned in the posts Class A amplifier, single ended, Emitter Follower.
In Class A the transistor is driven between its on point and saturation carrying the whole 360 degrees of the sine wave. The transistor in Emitter Follower configuration will give us power gain plus it is easier for impedance matching.

You are right that the Darlington pair is a factor but in this circuit it is more like a filtered power supply for the Linear amplifier. And it is another Emitter Follower.

When John refers to the impedance of the battery he means exactly this and not the voltage. And yes the impedance of the battery could be sensed through a voltage divider and op-amp. This is exactly how the linear regulators do it. Check the block diagram of a linear regulator given in the datasheets. And I think this is why John pointed me out in his responses to Servo Control. And it is one way to do it.

Hope that answers your questions.

I am awaiting to see what diagrams you wanted to post and than I will get to something you seem to skip.

Regards
Lman

[Joster]

Hey Lman, Thanks for replying...here she is hope it works

[Joster]

this should be better

[Joster]

here is another one ive been messing with