Programmable Voltage Source Idea

[[email protected]]

http://i38.tinypic.com/2qidapt.jpg

Will the above circuit work well in practice for a programmable
voltage source? The zener would be a similar idea to shunt the current
for over-voltages. I am in need of a medium power programmable voltage
source and this seems to fit the bill while being simple.

Thanks,
Joe

 

[James Arthur]

wtf????
How come this circuit looks bogus to me???

It's sideways. All the electrons will fall out the
bottom.

James Arthur

 

[James Arthur]

Just looking at the 339 makes me ill..

Yep. It's gonna oscillate something fierce.

My idea of a programmable V source uses a DAC.

"D from A C" ?

Grins,
James Arthur

 

[James Arthur]

And didn't they leave out the rotating magnets ?

...Jim Thompson

Yes, great catch. They did leave those out--and that's
the tie-in to mpm's free energy machine, the centerpiece
of our new green/renewable feelings-based energy agenda.

Cheers,
James Arthur

 

[David L. Jones]

http://i38.tinypic.com/2qidapt.jpg

Will the above circuit work well in practice for a programmable
voltage source? The zener would be a similar idea to shunt the current
for over-voltages. I am in need of a medium power programmable voltage
source and this seems to fit the bill while being simple.

You left out lots of important starting detail like:
- how you want to "program" it
- what voltage range you need
- what you mean by "medium power"

That circuit is silly BTW.

"Abstract Dissonance" - we haven't seen you here in a while...

Dave.

 

[James Arthur]

http://i38.tinypic.com/2qidapt.jpg

Will the above circuit work well in practice for a programmable
voltage source? The zener would be a similar idea to shunt the current
for over-voltages. I am in need of a medium power programmable voltage
source and this seems to fit the bill while being simple.

Thanks,
Joe

Okay, you haven't gotten many straight answers, so I'll
take a stab.

No, your circuit won't work. The LM339 is a comparator;
it'll oscillate in that circuit. The MOSFET might
oscillate too.

You can use an LM339 as a lousy op-amp, but it'd be
better to just use a decent op-amp. Or an LM317.

You'd get more sensible answers if you showed input and
output nodes and said something about your goals
and needs (accuracy, range, power output, load, etc.)

HTH,
James Arthur

 

[Dookie]

Okay, you haven't gotten many straight answers, so I'll
take a stab.

No, your circuit won't work.  The LM339 is a comparator;
it'll oscillate in that circuit.  The MOSFET might
oscillate too.

You can use an LM339 as a lousy op-amp, but it'd be
better to just use a decent op-amp.  Or an LM317.

You'd get more sensible answers if you showed input and
output nodes and said something about your goals
and needs (accuracy, range, power output, load, etc.)

HTH,
James Arthur

Well, I figured since you guys are so intelligent you would be able to
figure out what is going on. It is suppose to be a comparator and not
an op amp. It is not a difficult circuit to understand. Seeing how
rude the people are here it's not even worth trying to explain. I'll
come back in another two years and maybe the trash will have been
taken out. If anyone can't figure out the circuit then maybe they need
to go to sci.electronics.basic and hang out for a while. The circuit
works fine in practice and I'm not sure what your talking about with
oscillation. The comparator should oscillate to some degree and with a
bit of built in hysteresis it should be fine. Do you seriously thing
that the opamp/comparator matters? That alone tells me either you guys
don't care to pay attention and just want to be jerks. I used the
lm339 because that is what multi-sim had. Abstract thinking is
important but I guess they don't teach that in repair school? See you
guys in two years, hopefully you will have grown up by then.

 

[James Arthur]

Well, I figured since you guys are so intelligent you would be able to
figure out what is going on. It is suppose to be a comparator and not
an op amp. It is not a difficult circuit to understand. Seeing how
rude the people are here it's not even worth trying to explain. I'll
come back in another two years and maybe the trash will have been
taken out. If anyone can't figure out the circuit then maybe they need
to go to sci.electronics.basic and hang out for a while. The circuit
works fine in practice and I'm not sure what your talking about with
oscillation. The comparator should oscillate to some degree and with a
bit of built in hysteresis it should be fine. Do you seriously thing
that the opamp/comparator matters? That alone tells me either you guys
don't care to pay attention and just want to be jerks. I used the
lm339 because that is what multi-sim had. Abstract thinking is
important but I guess they don't teach that in repair school? See you
guys in two years, hopefully you will have grown up by then.

It actually is difficult to understand.

I don't understand how a 10k pot will handle 100 volts
without burning up, or why a circuit that's supposed
to be programmable doesn't have a programming input.
Or an output.

I don't understand why you'd think that the LM339 has
built-in hysteresis--it doesn't.

I don't understand why the apparent reference input to
this voltage regulator from hell is nailed to +5.5v,
which makes the whole thing look kind of useless.

I don't understand why you're using such a complicated
circuit to perform such a simple function so poorly.

I don't know why you had to go to all this trouble
just to fry a pot and a zener diode--is it a race
perhaps? To see which one will smoke first?

But that's just me.


James Arthur

 

[James Arthur]

(sci.electronics.basics added, at Dookie's suggestion)

Well, I figured since you guys are so intelligent you would be able to
figure out what is going on. It is suppose to be a comparator and not
an op amp. It is not a difficult circuit to understand. Seeing how
rude the people are here it's not even worth trying to explain. I'll
come back in another two years and maybe the trash will have been
taken out. If anyone can't figure out the circuit then maybe they need
to go to sci.electronics.basic and hang out for a while. The circuit
works fine in practice and I'm not sure what your talking about with
oscillation. The comparator should oscillate to some degree and with a
bit of built in hysteresis it should be fine. Do you seriously thing
that the opamp/comparator matters? That alone tells me either you guys
don't care to pay attention and just want to be jerks. I used the
lm339 because that is what multi-sim had. Abstract thinking is
important but I guess they don't teach that in repair school? See you
guys in two years, hopefully you will have grown up by then.

It actually is difficult to understand.

I don't understand how a 10k pot will handle 100 volts
without burning up, or why a circuit that's supposed
to be programmable doesn't have a programming input.
Or an output.

I don't understand why you'd think that the LM339 has
built-in hysteresis--it doesn't.

I don't understand why the apparent reference input to
this voltage regulator from hell is nailed to +5.5v,
which makes the whole thing look kind of useless.

I don't understand why you're using such a complicated
circuit to perform such a simple function so poorly.

I don't understand why you had to go to all this trouble
just to fry a pot and a zener diode--is it a contest?
A race to see which one will smoke first?

But that's just me.


James Arthur

 

[James Arthur]

I don't understand the person..
If I can't understand the person, there's a good chance I won't
understand the circuit either.


D from BC

A schematic reads like a window into its author's soul.
You can understand a lot.

I don't understand someone asking for critique,
then complaining when he gets it.

Cheers,
James Arthur

 

[MooseFET]

If it works fine in practice, why did your original post ask us if it
would work in practice? It's really goofy, but I suppose it might
regulate. Some.

Bye. See you in 2010.

I really liked the 0% pot and the "virtual diode". I looked in
digikey but they don't stock them. You make a nice 0.2V step
controlled supply like this.

------------------ To CD4051 Vcc and X7
!
!+\ LT1498
! >
!-/
!
+------------------ To CD4051 X6
!
!+\ LT1498
! >
!-/
!
+------------------ To CD4051 X5
......... Repeat 6 more times .....

Try it in LT Spice

 

[Archimedes' Lever]

Yes, great catch. They did leave those out--and that's
the tie-in to mpm's free energy machine, the centerpiece
of our new green/renewable feelings-based energy agenda.

Cheers,
James Arthur

Yeah... you can call it the Obaminator.

 

[ehsjr]

Yes, great catch. They did leave those out--and that's
the tie-in to mpm's free energy machine, the centerpiece
of our new green/renewable feelings-based energy agenda.

Cheers,
James Arthur

Yeah, but if they included them, the damn thing might
work, and we'd need a new unit of measure: Obamawatts

Obamawatt: the result after Obama taxes the shit out
of you and runs the money through his snake oil crapology
policies; analogous to the circuit at
http://i38.tinypic.com/2qidapt.jpg

Ed

 

[James Arthur]

Yeah, but if they included them, the damn thing might
work, and we'd need a new unit of measure: Obamawatts

Obamawatt: the result after Obama taxes the shit out
of you and runs the money through his snake oil crapology
policies; analogous to the circuit at
http://i38.tinypic.com/2qidapt.jpg

Ed

Now Ed, I think you're being overly pessimistic.

Why, I was driving home yesterday when I noticed my
fuel gauge had crept up from "E" to about 1/16th.

Then it hit me: "It's already working! Obama's filling
my tank!"

Cheers,
James Arthur

 

[ehsjr]

Now Ed, I think you're being overly pessimistic.

Why, I was driving home yesterday when I noticed my
fuel gauge had crept up from "E" to about 1/16th.

Then it hit me: "It's already working! Obama's filling
my tank!"

Cheers,
James Arthur

 

[Ben Bradley]

I don't understand how a 10k pot will handle 100 volts
without burning up,

That one's easy, it's a virtual potentiometer, so it has an
infinite heat sink.

 

[James Arthur]

That one's easy, it's a virtual potentiometer, so it has an
infinite heat sink.

Thanks, that explains it. Now how about when R5 is set
to, say, 100 ohms--how does that work?

Grins,
James Arthur

 

[James Arthur]

That comparator pointing up is like a raised middle finger.

John

Yep, that's how I took it.


No one's pointed out that the regulator-oscillator
loop never does anything useful: D1 never conducts.

Well, at least not until after R5 smokes...

http://i38.tinypic.com/2qidapt.jpg

Best,
James Arthur

 

[ehsjr]

Thanks, that explains it. Now how about when R5 is set
to, say, 100 ohms--how does that work?

Grins,
James Arthur

Well, D2 and R1 are made out of strongium, maybe even
virtual strongium, so ~8mA for the R or 1 amp for the
zener or even way higher won't hurt either one. As to
D1, it depends upon how virtuous it is, but that's
not specified, so for diminishing values of virtue,
the circuit gets dirtier and dirtier.

Ed