Fusion Success with Precipitator Power Supply

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Mark Rowley
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Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

After suffering the typical setbacks with using insufficient XRTs, I recalled several folks here discussing the cheap precipitator power supplies. Back in 2017, Finn Hammer conducted a very thorough review of the dual transformer 30ma / 30kv unit (pictured). Heres the link to Finn's excellent report:

viewtopic.php?f=11&t=11992&p=77914&hili ... ply#p77914

It was suggested that it may be good for a demo fusor and I recall reading about at least one group member using one to create a basic demo unit. Other than some periodic discussion, there wasn't much more about said about it.

Since I was mentally gearing up for a costly road trip to obtain a big heavy transformer, I decided to give Finn's unit a test with my system. Figured I had nothing to loose for a $50.00 investment and if it didn't work I could use it for other HV projects.

TBH, when it arrived skepticism was running high. Not only was it light and comparatively small, I was also expecting the overcurrent shutdown issues everyone discussed in previous threads.

So off I went to run another 220v line to the Fusor and to source a plexiglass platform for it to temporarily rest upon. Once done and energized, it produced a nice stable plasmoid. In fact, I had to quickly turn it down as the grid was getting red hot due to the 100mTorr pressure in the chamber. Obviously, lack of current was not going to pose much of an issue (at least for my small fusor).

After getting the diff pump running and the vacuum at suitable "fusion levels" I began running it through the paces. It became immediately apparent that it easily provides the current and voltages I need for the 2.75" fusor.

The plasma picture below was powered by this supply. The pic was taken at 27.5kV / 2.85ma / 35mTorr of Deuterium. The only reason I didn't push it to a higher current was due to the grid getting too hot (I'm still learning to slowly walk this thing up to higher levels). And once again I have to emphasize, no overcurrent shut down. And as Finn indicated earlier, this unit barely gets warm.

One concern that Finn brought up was potential flashover at voltages over 20kV. I have yet to power this up without a load (and may never do so), but when operating under load there's no telltale corona hiss or warning signs when going over 20kV. For a brief time I pushed it up to 32kV or so and may have heard a little hissing but nothing of great concern. I would suspect the 60kV unit may prove to be more of a concern but I have no plans on operating in that region. And if someone wanted to pot this in oil or silicone rubber, that would easily remove most of the concern.

In the next week or so I will be testing the larger 4 transformer 10ma / 60kV unit. I'll add to this post when it arrives.

Overall, I think this is a great entry level power supply for the Fusor enthusiast. It may not come close to breaking any records, but for $50 one cannot loose.

I'm looking forward to seeing more folks testing these supplies and pushing them to their limits.

Mark Rowley
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Dennis P Brown
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Re: Fusion Success with Precipitator Power Supply

Post by Dennis P Brown »

Good post. I was wondering, Finn was worried about arc over on the board by the HV above 20 kV. Was this an issue or did you put the unit under oil?

Also, could you show more details on the construction of your measurement devices for the voltage and current outputs? That would be useful for others here as well.

Finally, could you post on both your neutron detector setup and deuterium supply (assuming you haven't already) in more detail, too? These be of interest here relative to your setup. I assume you already posted details on your chamber.
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Re: Fusion Success with Precipitator Power Supply

Post by ian_krase »

This seems like it may be a game changer.

I'd be very interested in any details about wiring and schematic.
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

Specific to the 30kV version, there’s not much to wiring it up. Its output is completely isolated / floating, just like a battery. So it’s basically a matter of thoroughly grounding the anode and routing the cathode to the grid. Wiring the voltage and amperage meters is just as shown in the FAQ’s. Nothing new there.

Powering requiriments of the supply is standard household 220ac.

I haven’t tested the 60kv version yet but I suspect wiring will be similar if not identical. As noted before, you’d be taking chances running it up to 60kv without potting it in oil or similar.

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Re: Fusion Success with Precipitator Power Supply

Post by Rex Allers »

Great to hear that someone with some basic electric sense was able to finally put one of these supplies to good use.

I've only looked at the listings a while back. Am I correct that the pic with 2 HV transformers is the 30 kV version and 4 transformers will be 60 kV?

My guess is every transformer has a rectifier in series in it to make DC out. Does that sound right from what you know?

I always thought the biggest drawback for US users was the need for 220 VAC input. I wonder if they could be hacked to take 120 VAC input? I assume that like most switchers the input gets rectified to some high DC voltage that gets switched into the HV transformer primary. You probably never had any reason to check but I wonder if you can measure the DC voltage being switched on the board?

I'm wondering if hacking the input circuits could allow them to run with 120 by having a doubler configuration (if it isn't already doubled from 220).

Anyway congrats again for being the first to successfully use one of these supplies.

Maybe I should order my own and try it rather than just sitting here and speculating.
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Re: Fusion Success with Precipitator Power Supply

Post by Richard Hull »

If Rex is right,

1. Is the rectifier in backwards in these potted flybacks? (making the output negative). Thus far I have only seen 100% of these putting out a positive HV.

2. if just positive output, is the entire output two terminal floating and not grounded. This would allow you to ground the positive side.

I know that if you place a huge order for negative output flybacks someone will make them for you. ($$$$$$)
Of course just wire flybacks with no rectification will allow you to externally rectify to you hearts content.

Serial connecting floating flyback rectifier combos would create insulation issues, but spacing out the HV side and conformal coatings could offer a win.

I never poo-poo'd these supplies. Finn gave a good stab at this, but then he told us he would disappear for a time and hoped to return. His splendid efforts here are missed. The smaller cross fusors tend to get results at a bit lower voltages due to the pressures at which they are worked. I guess if all you want is a cheap highway to do fusion and get in the neutron club these supplies in crosses might do the trick. I watch all such efforts in these smaller systems to see how far they can advance on extremely low budgets. Joe Gayo is doing great, but has plus ultra gear in abundance.

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Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion Success with Precipitator Power Supply

Post by ian_krase »

Wait, you mean this thing can do either polarity just by selecting what becomes the ground??? Now that is interesting. I smell an accelerator project...
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

It's still baffling to me how folks will build a neutron producing Fusor (some being top notch) and then abandon the whole shebang after making the club. In all respects, this should be a new beginning. Lots more to do and learn. For me, this small scale platform allows things like grid design experimentation, power supply testing, D2O electrolysis improvement, video monitoring of the poisser, and neutron yield improvement.

On a side note, I attempted unsuccessfully to address a typo on the original post. The PSU was incorrectly listed as 30ma / 30kv. Its supposed to be 10ma / 30kv.

Ian, you and several others have mentioned the possibility of applying these to accelerator use. I think this is a great idea...especially with the 60kv unit.

I'll be posting more numbers soon. Need to finish a painting project first.

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Re: Fusion Success with Precipitator Power Supply

Post by Dennis P Brown »

The 220 volt service really shouldn't be an issue: most homes have 220 v service for their dryer and/or hot water heater (all main panels have this service - just two out of phase 120's.) An electrician could easily add an outlet if anyone wanted that in a given room (I easily added my own outlet for 220 service in my project room but I am experienced in wiring. Just remember, follow all State regulations relative to code and associate local law, first.)
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Re: Fusion Success with Precipitator Power Supply

Post by John Futter »

For a precipitator you need floating outputs so you should be able to wire either way by grounding whichever
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

You definitely can. The DC output it isolated from the line in.
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Re: Fusion Success with Precipitator Power Supply

Post by Bob Reite »

Ah, I wonder if these were designed to operate with the outputs totally floating, and that grounding one side (no matter which) might stress them. I ordered one to experiment with, once I get my hands on it, I will study the design and see if any special precautions should be made.
The more reactive the materials, the more spectacular the failures.
The testing isn't over until the prototype is destroyed.
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Re: Fusion Success with Precipitator Power Supply

Post by ian_krase »

Not really practical for those of us who are doomed to live in apartments.
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Re: Fusion Success with Precipitator Power Supply

Post by Bob Reite »

Well I broke down and bought the "600 Watt 60 KV" version off of Ebay. As far as getting 240 volts. I have been too lazy to run a 240 volt circuit to the attached garage, and if I wind up moving the fusor to "The Train Shed" and remote controlling it like Doug does, I would put the 240 volts out there.

So I had toroid transformer good for 1000 VA, and by connecting the various windings correctly I got a 120 to 230 volt transformer.

Now that I have one of these supplies in hand, I was able to determine that those are four flyback transformers with a built in 1/2 wave diode rectifier. Yes, they are getting away with hooking the HV secondaries in series and the primaries in parallel to drive with a two MOSFET half bridge circuit.

Well, As I suspected, the seller got his "10 mA" rating while it was only putting out 5 KV Best I've been able to get out of it is 2 mA at 25 KV for 50 watts. The voltage regulation stinks! If you leave the output control set where the device is giving 2 mA at 25 KV, and go open circuit, the output voltage will jump to 50 KV. Trying to get to a higher open circuit voltage makes things arc and trip the GFCI outlet. But the power supply does survive the abuse, maybe the GFCI tripping protects it.

Still deciding if I'm just going to "box it up and send it back", or redesign the driver, a full four device driver circuit that would have better regulation.
The more reactive the materials, the more spectacular the failures.
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

Hi Bob,
That's kinda odd and I'm wondering if your supply has some issues OR it's an specific issue with the 60kV unit. I can easily get 4-5mA at 25kV (even at 30kV for that matter). But this is with the smaller "two flyback" unit that's pictured above and what Finn used in his earlier post. I've never tried for any higher current due to concern of melting my grid.

I have yet to install the 60kV supply but it is here and on the bench. Time permitting I'll give it a run in the next few days. I'll report back once done.

Again, for those new to this subject, almost all of this was presented and explained in Finn's earlier report.

viewtopic.php?f=11&t=11992&p=77912&hili ... ore#p77912

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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

Bob,
You said your supply was arcing at higher voltages? Where exactly did the arcing occur and did you pot the supply before attempting to go over 20kV (or higher)?

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Re: Fusion Success with Precipitator Power Supply

Post by Richard Hull »

I wonder if they just threw two extra flybacks on the same electronics as the two flyback unit??

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Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

There seems to be a few more components on the 60kV version. Here’s a side by side comparison.

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Re: Fusion Success with Precipitator Power Supply

Post by Richard Hull »

Looks like a lot beefier half bridge transistors in the 60KV unit. Probably just a stronger simple driver circuit, but based on the new 4 flyback load at 60 kv,, as noted by Bob in experiment, it falls on its face. The 60kv unit tends to collapse when working a fusor.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

I need a few more details from Bob regarding his conclusion of 2mA at 25kV. Even though I have yet to put the 60kV unit through the paces, his claim seems very off to what I've see so far. What did he use for a load? Did he try to operate his fusor with it? If so, air or Deuterium? Did he employ a ballast resistor or no resistor? Chamber size compared to a 2.75" system? He claimed some arcing took place? details? Corona losses prior to arcing affecting current measurements? More details please. This will help greatly when I install the 60 later next week and make a comparative run with my Fusor. In the meantime I picked up the lesser known 40kV / 10mA supply. This one is similar to the 30kV unit but the flybacks appear about 25% larger than what's on the 30 and 60. I'll post results once I get around to testing it.

What I do agree on is the voltage regulation issue. Voltage output under load and no-load conditions could be wildly different. For example, if you are operating a stable plasma at 15kV and suddenly the plasma extinguished (causing no load) your voltage could instantly jump to 25kV or more (likely a lot more if using the 60). It would be crucial to make sure ones HV feedthrough and leads can withstand the full potential of this type of supply PLUS a healthy safety margin. Although they are comparatively tough, I'm skeptical if they can survive arcing for more than a couple of seconds. Beefing up the HV line and feedthru is clearly one of the tradeoffs for the inexpensive nature of this type of supply. Yes, more work has to go into HV handling, but it's still hundreds of dollars less (and immediately available) than the comparatively unobtainable continuous duty cycle iron cored transformer (or other well known expensive options).

Of course, this is all specific to it's intended use as a power supply for the 2.75" systems. I highly doubt it'd do anything for the classic large spherical fusor.

Bob, do you have any idea what the unmarked IC's are? I'm thinking the 8 pin is an op-amp similar to a LM358D but the unmarked 16 pin is a total mystery.

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Re: Fusion Success with Precipitator Power Supply

Post by Bob Reite »

Yes, it annoys me that they ground off the part number of the ICs.

I was using the fusor operating with air as my load. I can pretty well control the flow rate with the mass flow controller and the pressure with the exhaust valve controller.

I'm not sure what arced to what.

Next thing I want to do is install an insulated extension shaft and change the mounting such that I can safely operate the output control while it is running. That way I can get a stable plasma going then adjust that control. I have been turning the shaft a few degrees at a time with the power off, then checking my results by switching it on with a switch at a distance.
The more reactive the materials, the more spectacular the failures.
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Re: Fusion Success with Precipitator Power Supply

Post by Mark Rowley »

Installing an extension for the voltage control was the first order of business. It’s a 10k potentiometer which I replaced with a standard panel mount on an 8’ lead. I then mounted it in a plastic experimenters box and affixed an acrylic rod for control.

Aside from the mystery chip any thoughts on the two unmarked dip switches along the left side?

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Re: Fusion Success with Precipitator Power Supply

Post by Richard Hull »

14 and 16 pin ICs were typical of the early PWM chips. Just a thought.

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Fusion is the energy of the future....and it always will be
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Re: Fusion Success with Precipitator Power Supply

Post by Chris Giles »

An example:
http://www.ti.com/lit/ds/symlink/tl494.pdf
If you want to identify the chip, I suggest finding out which are the VCC and GND pins and matching that to various 16-pin controller ICs - look for the most common / cheapest ones.

Once you have identified the chip then you would stand a better chance of working out what the DIP switches are for.

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Re: Fusion Success with Precipitator Power Supply

Post by Rex Allers »

I've joined the fray too. I ordered one each of the 30kV (two transformer) and 60kV (4 transformer) supplies.

Unfortunately, the bigger one arrived with the HV output wire broken off where it comes out of the transformer. After a few emails with the seller, he is sending me another one of those supplies. But it's coming from China and will be a while before I get it.

Meanwhile, I started hacking the circuit board of the bigger supply. One good thing is that the circuit board is single sided -- only one layer on the bottom. I have begun my usual method.
1) I scan the board in a flatbed scanner to get an image of the traces.
2) In a photo editing program I draw in red circles on top of all the vias and then lines over each trace.
3) I select all the red as an object, cut it and paste it into a blank image.
4) I use a tool to flip it horizontally, so now I have an image of the traces as seen from the component side.
5) I print it out and start penciling on symbols for each of the components, so I can begin to see how things are connected.

I haven't got all the components on yet and I may have to redo some as enlarged sections because it is messy crowded. Anyone else care to join me on trying to figure it out?

So far:
The 8-pin chip. Pins 5 and 7 each have a 10 ohm resistor in series to the gate of the two big MOSFET transistors. So I'm pretty sure its a standard dual gate-driver chip. The first one I guessed didn't work with the power pins for the chip. A little searching and an IR2101 or 2102 seems to match pins.

Looks like there are two opto isolaters feeding the inputs to the gate driver chip. It doesn't look (to me, so far) like simple outputs from the 16-pin chip are doing the switching. I'm only getting the lay of the land at this point.

I hacked a CCFL supply a few years back. They used a gate driver chip and sampled voltages on the FET drives to make sort of a big flip-flop transitioning at zero crossings and resonate with the transformer. Maybe something like that is happening here.

The 16-pin chip. So far it doesn't look like a switching controller that I recognise. There is a 4-pin header near one end of the chip. Maybe the chip is a microcontroller and the header is to allow programming firmware.

There are two current sensing transformers on the board. One is sensing the AC input and the other is in the HV transformer primary drive.

There is a blue transformer. It takes the AC input and drops it down. That lower voltage feeds a 7812 regulator to make a +12V rail. It feeds the 8-pin chip. That rail then feeds a 7805 to make 5V. I think that the 5V is the supply for the 16-pin chip.

Anyway, that's some observations after a few hours of digging. I haven't gotten most of the components drawn around the 16-pin chip yet.

I'll post more if I get more details.

I do have a lot of apprehension about the daisy chaining of the 4 HV secondaries of the output transformers. I expect the low (minus) end of a secondary is near the core and probably wasn't expecting to be sitting on top of the high end voltage from previous transformers. That could be where Bob's arcing came from.
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