Wanting to make some negative DC to watch conventional current flow

[saturated]

I wanted to get my hands on some negative DC and see (ok we know it will  ) if it would pass through a diode from the cathode side

The first "circuit" I came up with in the midst of drawing it I thought oh wait this is gonna be a normal circuit we are just looking at it from another perspective but then I realized yeah no not quite

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I kept trying to figure out how to wire this up to get negative DC and about the best I could do was having to utilize an external ground

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Which seemed to work
For the ground i connected the positive terminal of PACO to the Ground terminal of my scope
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I slowly dialed up and adjusted it to about 5C DC

So I had -5V DC at the anode side of the diode
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And then -4.4V DC at the anode

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So I think I did this right and seems to agree with what I was looking for

Then I remembered well there's nothing wrong with the first circuit it's just that the cathode will be at zero  so I hooked it up and get about 0.67V DC at the anode

[saturated]

So what's all the fuss about yeah wow the sky is blue  is this breaking news ?

The point being that earlier before this I only considered conventional current flow I just knew "the positive flowed" in the direction of the arrow

All of this kinda worked until I started trying to figure out alternating current and diodes 

What would be cool is to see some negative fluctuating DC pass through 

[saturated]

The next phase was a little easier

Wanting to see negative fluctuating DC travel through a diode

I connected a diode and resistor same ones in series and added a signal to the cathode of the diode

Then put my scope probe on the anode side

When I had the DC offset of the signal at zero or above no signal passed through

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(Sorry I have no idea why my phone camera only gets a fragment of the green lines)

Now if I turn the DC offset negative the signal can be seen at the anode side of the diode

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[g1]

What makes you say "this is not negative, it is ground" ?
From the PACO schematic, the (-) terminal appears to be floating, not grounded.  So you can connect the (+) output to ground and you have a negative supply at the (-) terminal.  This seems to be what you did anyway.

[g1]

When I had the DC offset of the signal at zero or above no signal passed through

Your signal wasn't big enough.  If it had been big enough, the peaks beyond the diodes forward voltage drop would have got through and you would have seen the negative alternations of the sinewave.  This would have been rectified but unfiltered DC.

When you added the DC offset, you 'biased' the diode to be on, so the complete sinewave was able to get through.

[saturated]

Yes sir thanks I will do that 

Ok I was gonna spare you the gory details but anyway

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I need to figure out why I have a complete green 🍏 line in real life but when I take a picture I only get partial fragments

[Kaz Kylheku]

What do you mean by "negative DC" though? Anti-conventional current, i.e. flow of negative charge?

Both currents are always present together, opposite and equal.

If there is a chemical cell battery in the circuit, inside a battery, both kinds of charged particles, anions and cations, are present and moving in opposite directions.

Imagine you have a circular ring of copper with current moving around in it (perhaps induced magnetically).  If, in our frame of reference, we spin the ring in the opposite direction of electron flow, we can get the electron current appear to stand stil. Then what is moving in circles is the nuclei of the copper atoms (together with any lower shell electrons that don't participate in current). That's a real flow of positive charges.

In other words, in a wire, the fact that protons are not moving while electrons are de facto means that the protons are moving in the opposite direction. If you could ride on top of an electron, you would be leaving protons behind in the rear view mirror, and that's essentially your conventional current flow.

It's like the wind in your face when you're on a bike. The air may be standing still on a windless day, but you have "conventional wind" in your face. 

What is an intepretation of conventional current in a vaccuum? Electrons are shooting from the cathode of a tube to the anode. Nothing is flowing backwards. But again, if you could ride on top of an electron, you would see that the more positive anode/plate is rushing toward you.

[saturated]

Yes sir thanks I appreciate the input to the discussion 

I kinda see your point

For instance I can pop the hood on my 1980 Bronco and measure 12.6V DC or whatever

Then I can switch the probes and go hey look now I've got minus 12.6V DC

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So perhaps it's all relative 

That's why we have to use reference to ground to make sense of it all

I guess

I mean c'mon man you a lot more about this stuff than me 

But obviously alternating current is real 

[J M Fahey]

There is not negative or positive by itself, voltages are always relative to some other value.
If you have a battery and ground positive end, the other end gives you negative voltage.
All normal voltage souces have both.

That said, *electrostatic* voltage sources, such as when you repeatedly wipe a piece of plastic with a piece of dry cloth, can be "unipolar" which can be checked by what they attract, such as dust, lint, etc, but they can not supply a current, light a lamp, run a motor, etc.