Electron gun- what's wrong here?

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Steven Sesselmann
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

Jeroen,

Yes, it will behave like a triode, however it is not irrelevant at what potential an atom becomes ionised, and in a fusor you will get more fusion when you create low potential ions. The way to do this is exactly as David is doing, one could go a step further and lower both the ring and the filament together, making sure there is enough differential to generate a stream of electrons.

As for the Coulomb force and the gravitational force for that matter, have you ever seen either?

I would be most surprised if you said yes, because I have never heard of anyone observing any of the four fundamental forces we are being taught about, the fact is we observe constant or accelerating velocity and so as to not look like idiots, the so called educated people gave it a fancy name like "Coulomb Force", "Gravity" etc. and those who were not so smart bought it.

Unicorns that's all they are, and the sooner you spot them the sooner they gallop away..

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Jeroen Vriesman wrote: Having the filament and the anode ring both biased with an negative potential is the same as have a higher positive potential on the target, but with the side effect that the chamber walls are positive with respect to the electron source, this will pull the electrons to the walls of the chamber.
I understand that the chamber walls and nipple the electron source is contained in would be positive w/ respect to the negatively biased source. But with Gauss' Law, wouldn't there be zero E field inside the nipple and the spherical chamber to pull the electrons to the walls? Or is it really just a matter of the negative fields pushing the electrons away, and some of the electrons just happen to find their way to the walls which then simply go to ground?
If your experiment needs statistics, you ought to have done a better experiment.

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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

Having the filament and the anode ring both biased with an negative potential is the same as have a higher positive potential on the target
This statement which is widely believed to be true is a false statement. I think I have a reasonable argument for absolute potential and for the statement above to hold true, potential would have to be scalar. A particles velocity appears as a function of it's potential with respect to the observer, so yes Schroedinger was right, it does depend on who is looking.

Steven

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Re: Electron gun- what's wrong here?

Post by Jeroen Vriesman »

Hi david,
But with Gauss' Law, wouldn't there be zero E field inside the nipple and the spherical chamber to pull the electrons to the walls?
Yes, but only if there are no objects in the chamber with some other potential. If you have something inside your chamber at a potential U, and the chamber is grounded, the electric field is about U/d (the shape of the field can be much more complicated, U/d is just an indication) where d is the distance between the object and the wall.

In my experiments involving emission I have to make the filament a bit positive to avoid all the emission current running between the filament and the chamber walls.
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Re: Electron gun- what's wrong here?

Post by Jeroen Vriesman »

Hi Steven,

in your reference you seem to state that potential is limited because relative velocity is limited, however, the energy associated with relative velocity is not limited, it goes to infinity near the speed of light, so the potential is not limited. You are using the special theory of relativity in one argument, but you skip it for the conclusion.

There is some truth in force being an illusion, Newton already knew that his theory of gravity was problematic, it introduced a "mysterious force working at a distance".
However, the problem is not physical, it's a psychological problem, the idea that some kind of "contact" is needed for a "force" is just a result of our size and the way humans experience the world. All "forces" work at a distance, when we push things around there is not a single molecule actually touching another molecule.

What's happening is that the phenomenon we call "force" is just the first derivative of the total energy of the system, we just exchange forms of energy, gravitational, electrical, thermodynamic energy etc.
When we push against a wall it just means that we do not shift enough energy from one place to another to push our hands through the wall, "contact" just means "not having enough energy to change the state of the matter involved".

This insight leads to some very useful mechanical methods, called the Hamiltonian and Lagrangian, https://en.wikipedia.org/wiki/Hamiltonian_mechanics

So there is just the potential of the system. Thermodynamics show us that states which can be solely described by information theory still represent an energy, so the whole thing can be modelled as information only. Attempts at modelling gravity that way have recently been made by Verlinde https://en.wikipedia.org/wiki/Entropic_gravity

So indeed, "force" can be considered less fundamental than potential, but potential is not limited by the speed of light, since the energy needed to reach the speed of light goes to infinity.

In physics the EM theory is considered a "gauge" theory, the potential of the system as a whole can be varied without changes in behaviour.
Only by assuming the entire universe does not have a net charge one could define the absolute zero potential. (the idea that the potential at infinity is 0)

That force (and even the derived concept of a "field") are less fundamental than potential is experimentally proved by the Aharonov-Bohm experiment https://en.wikipedia.org/wiki/Aharonov% ... ohm_effect, a wonderful experiment!

As for your "second case for absolute potential"... seems to me a case of "not even wrong". Choosing the proton is arbitrary (if you take a charmed lambda or sigma particle you get different "absolute maximum" potential), equating the equivalent energy to surface potential, stating that a collection of protons has the same surface potential as a single proton (without even defining the "surface" of the charge collection)? Strange stuff.
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

Jeroen Vriesman wrote:Hi Steven, in your reference you seem to state that potential is limited because relative velocity is limited, however, the energy associated with relative velocity is not limited, it goes to infinity near the speed of light, so the potential is not limited. You are using the special theory of relativity in one argument, but you skip it for the conclusion.
Jeroen, you make an important observation, because in my paper I talk about "potential" not "potential energy", the two terms are often confused. When you divide potential energy i.e electron-volts by electrons you just get Volts and the unit Volt is a measure of raw potential and it has to be limited.
Jeroen Vriesman wrote:There is some truth in force being an illusion, Newton already knew that his theory of gravity was problematic, it introduced a "mysterious force working at a distance".
However, the problem is not physical, it's a psychological problem, the idea that some kind of "contact" is needed for a "force" is just a result of our size and the way humans experience the world. All "forces" work at a distance, when we push things around there is not a single molecule actually touching another molecule.
Correct, I agree and we need to keep in mind that the terms forces and fields are mathematical constructs of the mind which have no physical reality, but help us calculate the velocity, which is really all I am saying in my paper, that the term potential refers to velocity or change of velocity.
Jeroen Vriesman wrote:What's happening is that the phenomenon we call "force" is just the first derivative of the total energy of the system, we just exchange forms of energy, gravitational, electrical, thermodynamic energy etc. When we push against a wall it just means that we do not shift enough energy from one place to another to push our hands through the wall, "contact" just means "not having enough energy to change the state of the matter involved". This insight leads to some very useful mechanical methods, called the Hamiltonian and Lagrangian, https://en.wikipedia.org/wiki/Hamiltonian_mechanics
Agree..
Jeroen Vriesman wrote:So there is just the potential of the system. Thermodynamics show us that states which can be solely described by information theory still represent an energy, so the whole thing can be modelled as information only. Attempts at modelling gravity that way have recently been made by Verlinde https://en.wikipedia.org/wiki/Entropic_gravity
So indeed, "force" can be considered less fundamental than potential, but potential is not limited by the speed of light, since the energy needed to reach the speed of light goes to infinity.
I would agree, force is less fundamental than potential and potential is less fundamental than velocity, because velocity is what we actually observe, so why is it so hard to see that potential is limited when we ultimately measure potential in velocity?
Jeroen Vriesman wrote:In physics the EM theory is considered a "gauge" theory, the potential of the system as a whole can be varied without changes in behaviour.
Only by assuming the entire universe does not have a net charge one could define the absolute zero potential. (the idea that the potential at infinity is 0)
This is where my ground potential theory diverges from the standard model, because the term you used above "entire universe" implies that we somehow act out our lives in a domain called the universe, I see this concept as fundamentally flawed. In GPT the observer is floating at ground potential and by manipulating it's own potential it changes the relative universe. I came to this conclusion because the GPT equation which relates the mass of the electron to ground potential is non local, i.e. when you as the observer climb a set of stairs, you increase your absolute potential which reduces the mass of an electron everywhere, so you are basically turning back the clock of your whole Universe not just your own clock. Think carefully about this.

It is also an outcome of the theory that space everywhere is at ground potential, this means our current understanding that looking out into the universe is equivalent of looking back in time is wrong. What we see when we look out into space is NOW on the absolute time scale, we see the sun as it is now and we see the moon as it is now. True light travels at a finite speed, so if we see the moon as it is now, then it's also in our future as we see it. So the light cone changes shape.
Jeroen Vriesman wrote:That force (and even the derived concept of a "field") are less fundamental than potential is experimentally proved by the Aharonov-Bohm experiment https://en.wikipedia.org/wiki/Aharonov% ... ohm_effect, a wonderful experiment!
Skim read it, but it's not something I can understand in reading it once, my initial reaction was that the experiment is flawed because it's measuring the velocity relative to the local fields and ignoring the observer, this is the general trend with quantum experiments and the reason why everyone is puzzled about quantum behaviour, they forget to consider the observer. When three people stand around the box containing Schroedingers cat, there are three observers and three realities, and not one realitry because there is one box and one cat.

Jeroen Vriesman wrote:As for your "second case for absolute potential"... seems to me a case of "not even wrong". Choosing the proton is arbitrary (if you take a charmed lambda or sigma particle you get different "absolute maximum" potential), equating the equivalent energy to surface potential, stating that a collection of protons has the same surface potential as a single proton (without even defining the "surface" of the charge collection)? Strange stuff.
Protons are a pretty good candidate, I have always been fascinated about protons, where they come from and why they are all identical, as a manufacturer I envisage some machine mass producing these particles that make up 99.945% of everything. They also happen to be the most energy dense naturally occurring particle, number one on the table of isotopes, which is why I chose the proton as the upper limit to potential. if there was another particle heavier and denser it would sit above and before Hydrogen on the table of elements, but noop I doubt you will find any stable particle up there.

938 million volts is just another way to express the speed of light c, the only reason the units are different is because we have messed up the units. So to normalise the units in GPT I simply multiply the speed of light by the fraction of absolute potential, and I can find the velocity of any particle with this simple equation.

∆v = c(∆U/Ø)

You can also write it like

∆v = ∆U (c/Ø)

Where c/Ø simply fixes up our stuff up of the units and ∆v = ∆U simply says velocity is exactly the same as potential.

Steven
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Re: Electron gun- what's wrong here?

Post by Dennis P Brown »

A quick edit error: You say
When you divide potential energy i.e electron-volts by electrons you just get Volts ...
and of course, the unit of electron-volt cannot be divided by electron to produce a volt. The unit is named electron-volt. One does not divide equations by a physical material but only by numbers or numbers with units.
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Re: Electron gun- what's wrong here?

Post by Dennis P Brown »

Another point; you say
protons make up 99.945% of everything
. You are forgetting neutrons.

Also, protons may or may not be stable - one may assume it is but that isn't the same as it being one; so why not use neutrons for your potential since these are heavier than protons and are very stable when bound with a proton. In fact, some table of the elements use the neutron ... .
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Re: Electron gun- what's wrong here?

Post by Richard Hull »

What began here as a failed electron gun project has devolved or evolved, your choice, into a theoretical discussion. Let's stay on topic in this thread.

I suggest another forum and a new thread if some wish to continue this offshoot.

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

I put the circuit together with all the right parts. Feeding it 5V DC, the HV probe initially shows 4-500V (occasionally catch it at around 1kv with an initial power on), but it would quickly fall to around 300V. And repeat each time I cycle it on and off. With just the circuit board minus diodes and caps, etc., I measure only 43V AC on each of the 2 outputs. When it measured only 43V on the HV probe, I tried just hooking up the DMM to it, but it flips out and goes blank. Not what it's supposed to be doing. Could it have been damaged when I had it mis-wired with the microwave diodes?
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

David, you should be measuring lower than -1000V after its rectified, and after the load resistor. Your DVM may not like voltages over 1000V and I wouldn't try measuring the 30 kHz AC side.

For this kind of measuring it's a good idea to make yourself a 1/1000 divider with a 1G/1M resistor, so 1V = 1000V

PS: Can you draw the circuit please.

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Apart from occasionally going over 600V, I see now why the DMM wouldn't like it- 60 Hz vs 30kHz. My HV probe output is divided by 1000 already.
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Re: Electron gun- what's wrong here?

Post by Dennis P Brown »

HV probes work terribly in that low end range; while hand held multi-meters just tend to fail in that same range since it (due to various factors) tend to read lower voltages than the actual voltage, which quickly exceeds the rate level of the meter causing it to fail.

Why not just make your own divider as Steve said (two cheap, low power resistors and that's it - his example works fine) for the multi-meter? So very simple - just design the range for the the high end being 2000 volt range and you are both safe and handle this grey area that doesn't have a good easy to buy solution relative to hardware.
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Re: Electron gun- what's wrong here?

Post by Rex Allers »

[Arrgh. I guess I flubbed submit. Second try on whole post.]

David,
I'm not sure what is going wrong but I do see one problem. For the output voltage this TDK CCFL supply can make, a single 1 KV diode is too low a voltage rating.

Rather than doing a lot of speculation, I decided to test. As I mentioned in an earlier post, I have a TDK CCFL module that looks like yours. A while ago I was doing some testing on a different supply and had the prototype I used with a simple rectifier and a divider for measurement. I reconfigured to attach that output to the TDK. Here are pic of what I used.
TDK CCFL with rectifier. Original test supply greyed out for clarity.
TDK CCFL with rectifier. Original test supply greyed out for clarity.
TDK test circuit. Simple rectifier and measurement voltage divider.
TDK test circuit. Simple rectifier and measurement voltage divider.
In the circuit diagram, on the left, I have shown the TDK module with its basic output circuit. I have bypassed the two caps by connecting to point 'A' to take the output directly from the transformer. On the right is my voltage divider for measurement. The main dropping resistance is 300 M ohm (three 100 M ohm resistors in series). The output is measured by a DMM across ~300 K ohm. Earlier, I had calibrated this ~300K value to give near exact 1 V out for 1 KV HV, or divide by 1000.

Testing the circuit with +5 VDC into the TDK module, I measured 1.26 V, so 1.26 KV output. I got about 1 KV out with about 4 V in. Therefore the 1 KV rating on your diode is probably exceeded a good bit. The diode I used is rated for 10 KV which is overkill in this circuit and probably drops the HV out a bit below what it could be.

The circuit you used is a voltage doubler which uses the caps on the TDK board. To verify it works the way I expected, I reconfigured the circuit and added a second diode to match your circuit. Here it is.
TDK test with voltage doubler.
TDK test with voltage doubler.
It did work as expected and with 5V in, I measured 2.5 V or 2.5 KV out.

So I'm not sure if exceeding the rating of 1 KV for your diodes by 26% is enough to kill them or not. For each of the diodes in your circuit you should be using two 1KV diodes in series.

In your last post you mentioned frequency. Some notes I have from earlier say this TDK supply probably runs the transformer at about 50 kHz, but that shouldn't matter. The caps in either of these circuits should filter out most of that to effective DC on the output.

It wouldn't surprise me if there is someting going wrong with the probe you are using to measure, too. In the last posts you haven't said much about what it is and I didn't go back to look if you covered that earlier. Do you know what its input resistance is? For not overloading this small supply, it should probably be at least 100 M and higher is better. My divider in this test is about 300 M.

You didn't say anything about how you constructed the circuit, either. I built this test by soldering "flying" components above a ground plane. This isn't the kind of voltage and frequency to try with one of those white plastic pluggable prototyping boards.

So as I have shown, it should work. I hope something here gives you a hint why it isn't working for you.
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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Thanks for all the info everyone. Thanks for going to all that trouble, Rex.

Probe info: 1-40 kV DC, divider ratio 1000:1, input resistance 1000 M Ohms- nominal. Also checked it against my main HV PS and its meter. In good agreement from 200 to 3 kV. (Hard to adjust it below 200V.)

Seemed the easiest route to try first was what Rex suggested. I re-wired it with 4 unused diodes. (Happen to have bought 6 total.) 2 diodes in series in place of each one. This time I got a max of 1800V, but it drops steadily until about 3-400V in a matter of seconds when I'm measuring it with the probe, and then stays there even after I remove the probe, "let it rest", and test it again- until I cycle the power to the inverter.
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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Thought I 'd check it over one last time. Found one questionable connection. Also, I was setting the DMM to V so I could mentally multiply the result by 1000 and not have to wonder what units it's in. Turns out this screws it up somehow. (It automatically goes to mV when powered on.) Between the connection and leaving the DMM alone when I turn it on, I easily and very consistently get a reading of exactly 2,300V DC! Looks like I'm out of the woods and learned a few things along the way.

I don't have an oscilloscope. This should be a fairly smooth, continuous DC output- not pulsed- right?
If I understand this right, each output from the inverter is 5 mA max. So 10mA if wired together like I have them? Will the max mA drop proportionately to the increase in V with the doubler circuit? And also, the V will drop if much of a load is placed on it? I suppose I could measure the V again when it's hooked into the filament circuit and running on the chamber.
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Re: Electron gun- what's wrong here?

Post by Rex Allers »

Did it again. Typed for about half an hour but didn't save locally and it went poof when I submitted. Maybe I wasn't really logged in?

Shorter version...

Good to know you got some output results that look good.

I checked numbers on the module here and it is CXA-L10A. Same as you and Steven.

Found basic data here:
http://www.tdk-lambda.com/products/sps/ ... bodye.html
and you can download full datasheet from there. Datasheet has a configuration they call Connection A, which is the two output caps in parallel as for the doubler circuit. There is a section of data specific for that.

Datasheet says 900 Vrms into open load. With simple rectifier and light load we will measure peak voltage or 900 * 1.414 = 1273V. Very close to what I measured before.

Then data sheet then says typ. 10 mArms, but that is into about 27 kohm load. Ohms law says the output voltage at 10 mA is only 270 Vrms! Not uncommon: take your pick, voltage or current. Don't ask for both at same time.

I decided to measure again. Configured back to simple half-wave rectifier (see my last post). Found some resistors: 68K 5w and two 10K 3W. Put them in series; measured 86.6 kohm. Used that as load on supply. I got it cranked it up as far as 674 V out, but that was at input of about 5.2V at 1.5 A. That's pushed beyond rated input. Ohms law says output current was 7.8 mA ; about 5.24 W. The 68K 5W resistor got pretty warm in minute or so at this level.

So to get into the ~1 KV range at mA current, will require the doubler. Lets say input of 5V at 1A might be a safe steady state level. In my measurement the supply efficiency was about 67%. If that held, and we can get 1100 V out of the doubler, the current would be about 3 mA. But the doubler will have losses too. I didn't measure more, but I would think if you can get around 1100 V out, you'd be doing good if you can see 1 or 2 mA.

At no load I would expect very low 30 kHz ripple on the HV DC. With these mA current levels through the doubler, I would expect a lot of ripple.

Fun measuring. I'm actually pretty impressed at what these little switchers can do.
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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Thanks again for going to the trouble. 1100V and 1 to 2 mA is hopefully enough for what I'm doing. Floating the HV output on the filament shouldn't draw much current- maybe even in the uA's range? The only energy being used is to accelerate the e-'s away from the filament. I'll find out as soon as I find the time to get it hooked up on the chamber. Then hopefully start seeing e-'s fly and measure the final HV the circuit can put out with the filament on.

When I was getting frustrated with getting this circuit to work, I found some Universal Voltronic PS's and thought about getting one and giving up on this circuit. About the same vintage and make as my main HV PS (about 1/2 century old), but not quite enough V or A for a fusor. Could probably get one to my door for about $250 and I got something I could always resell. I'll keep this as my fall back strategy if the inverter comes up short of what I need.
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Re: Electron gun- what's wrong here?

Post by Richard Hull »

As an old vacuum tube guy and a guy who has worked in technical vacuums of 30 to 5 microns .......A good emitting filament close to a plate of opposite polarity in anything less than a 10e-6 torr vacuum might tend to draw a gang o' current (townsend avalanche) and drop a high impedance supply to its knees. I am sure you will report to us on this. Your vacuum level will be the factor here.

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Everything has been thrown together on the chamber and tested (10e-6 Torr range). Best way I could figure to test it is with a central anode (main HV PS switched to positive output). The filament about 10 inches away. With + HV at about 3kV, and the 12V filament switched on, it doesn't draw any e-'s (Nothing on the main HV ammeter). Same conditions and turn on the inverter, and it shows several mA. If the + HV goes much higher, looks like a townsend avalanche- the mA's start going sky high fast, and the main HV PS trips off pretty quick.

FWIW, the accelerator ring that I built into the conflat is just sitting there- not even connected to ground.

With the HV probe, the inverter still shows 2300V with the filament off, but drops to a measly 100V with the filament on!
I get the same results (100V) without the central anode switched on. Apparently I'm getting the same number of e-'s ejected- they're just going to ground when they hit the opposite side of the chamber wall?

Something new also occurred to me lately. I have the filament transformer on the isolated transformer, but wondering about higher V's. Apparently 2300V isn't a concern. Say10kV was being put on the filament. The entire circuit the filament is supplied by is now floating at 10kV. Is there some point where there is danger of arcing to anything conductive nearby? Does that whole circuit have to be isolated/insulated to withstand the kV?
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

David,

That's correct, whatever power supply you use to heat the filament needs to float, so you need an isolation transformer.

In a fusor situation it is unlikely that you will need 10's of kV isolation because (as you discovered) you only need a few hundred volts to 1000V on the filament to make it emit electrons, those electrons will ionise some gas and keep your fusor lit at low pressures.

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Is there any problem with using a battery for the filament PS? I had a 12V lead/acid motorcycle battery in mind. The whole battery would be floated to whatever HV potential is used on the filament.
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Re: Electron gun- what's wrong here?

Post by Steven Sesselmann »

David,

No problem at all, I do the same on my rig, floating two 18V cordless drill batteries to power an MFC a USB hud and a DAQ.

Check the current draw and work out how long the battery will power it.

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Re: Electron gun- what's wrong here?

Post by David Kunkle »

Thanks. Just wanted to make sure. It sounded OK in my head, but on the other hand, I could do without a battery exploding. I'll just make sure it's electrically insulated well enough from everything else.

My filament will use 6W @ 12V. So it should last many, many times longer than I need before I'd have to recharge if I go with the motorcycle battery.
If your experiment needs statistics, you ought to have done a better experiment.

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Rich Feldman
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Re: Electron gun- what's wrong here?

Post by Rich Feldman »

>> I do the same on my rig, floating two 18V cordless drill batteries to power an MFC a USB hud and a DAQ.

You can also electrically float a cordless drill with _no_ batteries, and use its motor as a generator.
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