DIY Turbopump Controller

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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Oh geez, I'm super sorry, missed that!
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Re: DIY Turbopump Controller

Post by John Futter »

Nicolas
I have looked at your circuit
I did not use a micro directly to generate the drive frequency due to the danger of a reset or port hang from it.
There is a huge amount of stored energy in a turbo that is why in my diagram it was driven from the 4046 being used as a voltage controlled oscillator through a low pass filter that delayed abrupt voltage changes to the 4046. This filter should be changed to suit differing turbos ie longer time constant for 150 and 360 model pumps. Of coarse you change the buss rail voltage to suit these bigger pumps ie 14 / 28 volts for the tmp 360 and higher current mosfets and dont forget to lower the zener voltage in the buss protector
Fusor use includes high voltage power supplies and there will be the odd high voltage flashover that may reset your micro.
I certainly would not direct drive from a micro a larger turbo than the tmp50 due to the stored energy being released.
Even our turbo controllers have had the PSOC reset and the pump scream to a stop ( that what the big mosfet is for across the DC buss so that the electronics is saved from overvoltage from the motor back emf
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Thanks for the clarification John, I think I've misunderstood something fundamental about the operation of the circuit. I'm going to have to digest your post and look over things.
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Re: DIY Turbopump Controller

Post by John Futter »

You are doing alright I'm just giving a bit of sage advice learnt from doing wrong it in the first place

ask away and i'll answer
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Hi John

I have a TMP 50 so I'm dealing with one of the smaller pumps. But my general understanding of the circuit is that you use some discrete logic to generate the signals which drive the half bridge connected to the 3-phase motor of the pump. I had assumed that hooking up the microcontroller to the logic chips you'd used would have provided enough of an innate buffer to prevent damage to the microcontroller. Looking at my circuit again and your comments I assume the problem is with the current measurement portion of the circuit correct? I expose the microcontroller to large changes in voltage/current at that point. If I included some sort of opto-isolation on that connection would I avoid the problem? I've never used opto-isolation in a current sensing application before.
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Re: DIY Turbopump Controller

Post by John Futter »

Nicolas
It is hard to use linear optos to get volt and current sense across I make sure that there is series impedance then 5 volt TVS diodes across micro I/O pins

my comments were directed at some of the other posts where micro derived drive signals are use to drive the half bridge directly
a TMP 50 has about the same energy as a .22 LR cartridge where as a TMP150 is more like a .308 cartridge amount of stored energy
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Thanks for the clarification John, I've added the suggested circuit protection, now I just have to spec everything and layout the board! That's a nice way of thinking about energy as cartridge size, it's been awhile since I've been on a range but even though .22 LR is small I wouldn't want to be hit by either.
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Re: DIY Turbopump Controller

Post by Michal Dvoracek »

Hello,

I'm finally built up my turbo controller which is inspired by John's but it also contains speed measurement control.
I'm attaching some photos and video is here: https://youtu.be/OWJsfk7cNfQ

Regards,
Michal
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Re: DIY Turbopump Controller

Post by John Futter »

Excellent
looks similar to mine. I could not post the digital controller as it was code written at work hence ip problems ..

But well done
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Re: DIY Turbopump Controller

Post by Richard Hull »

Michal, a true love's labor and a grand win. I applaud both your and Nicolas' effort in electronics. I call it the hands on imperative or a "doer", doing. The epitome of the thrust of this site and of real amateur science is obtaining and retention of hard won skills that not only make life more full and rewarding, but in the making of a whole, capable person. You can be proud of your effort, you have earned the right to pride of accomplishment. Also laudable is the aid offered by John Futter and others in the quest.

I am sure that all here realize this is but a micro win in a demanded technology, (obtaining a scientific vacuum), along the road to the fusor and fusion quest here. One must never underestimate just how tough, costly, and demanding this amateur effort is to one's time and purse required for the acquisition of both knowledge and materials. It is not for kids. Big boy pants are needed if this task is taken on by any individual.

In the end, a win is laudable, but a win with useful experiment applied to the win is the ideal.

Note: the pep-rally is over. You can all get back to it....

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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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Very nice Michael! Would I be able to see your code and schematics? Always interested in seeing how problems I have to solve were solved!
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Just a quick update here. I've specced all the components for the Turbopump controller over the christmas break and now I'm getting in to the PCB layout. Lots of little details left to work out!
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Dennis P Brown
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Re: DIY Turbopump Controller

Post by Dennis P Brown »

Extremely impressive; your own design (yes, inspired by John's)? This is rather advanced level electronics driving a turbo - they are not simple motors. This is EE level work. That doesn't even cover the actual execution/build you've done.
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Thank you for the compliments Dennis, I still have to get it to work! The circuit is John's design, I've added a microcontroller to run the whole thing, but that's it.
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

I've completed most of a first draft of the routing of the board. I can post the KiCAD files if anyone wants to take a look but some details still need work. This is the first time I've routed a 4-layer PCB and a board of this complexity. I'd appreciate any constructive criticism more experienced hands might have to offer.

1. Is there a rule of thumb for controlling trace size given the power running through them? I've made the traces going out to the motor much bigger, but I have 5V, 15V and then motor power traces all running on this thing, and I haven't changed either the 5V and 15V traces
2. For a 4-layer PCB I've made one of my planes the ground plane, and was planning on making the second some sort of power plane. I assume I should make it the power plane for the power traces supplying the motor, is this correct? Or should it be the 5V or 15V power plane?
3. Is it generally acceptable to put component labels inside the outline of a component? I'm having trouble getting all the labels to be visible.
4. How do I size vias for different trace sizes, so far I've just been using the default settings in KiCad, but that clearly won't work for my thickened high power traces
5. Any general constructive criticism about the layout of the board and the traces would be much appreciated!
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Joe Gayo
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Re: DIY Turbopump Controller

Post by Joe Gayo »

Saturn tools for trace calculations ... https://saturnpcb.com/saturn-pcb-toolkit/

Think about where the high current loops are and make those as tight as possible.

The power plane can be split amongst multiple voltage rails.

There is an excellent video on PCB layout about how power actually travels in the dielectric space. https://www.youtube.com/watch?v=ySuUZEjARPY
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Thank you Joe, lots of good stuff to work through and learn! That PCB layout video is fantastic! I'm only a 1/4 through but so far it's been hugely enlightening.
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Re: DIY Turbopump Controller

Post by John Futter »

Nicolas
that looks pretty good
ie no input lines to micro going anywhere near the 3 phase output driver
you will see that the motor peaks at about 1 amp during rampup ie a hundred odd watts and with no gas load settle to about 6-11 watts at full speed.
have fun
oh and if it turns the wrong way interchange any two of the 3 phase outputs
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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Just a quick update on the progress of this controller. I've received the first draft of the PCB in the mail, and had built up nearly the complete board before discovering a couple of errors which means I'll have to do a second revision. They are as follows:
  • Double placed one footprint (see if you can find it!)
  • Polarized capacitors are packed too tightly, I cannot place all 5 with the current footprint layout
  • Holes for a diode bridge are incorrectly sized and the component does not fit
I've got a little cheap hot air setup here, so I figure I should be able to salvage all the bits without too much trouble.
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Re: DIY Turbopump Controller

Post by John Futter »

Drat
comes to mind
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Richard Hull
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Re: DIY Turbopump Controller

Post by Richard Hull »

I have put out a few custom boards and stupid mistakes are common and all part of the learning experience. The last two designs I had run were perfect. All the best in the rework. It is obvious you can save this first pass using good skills in work around assembly.

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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Nicolas Krause
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Happy to report I've got a decent prototype version of the board going. The eagle-eyed amongst you will note this is rev. 3 and I did find a final 4th serious error that required a respin of the board (thank you cheap chinese PCBs!). I've nearly finished soldering up the whole thing as the photo below attests too. The next step is to write a little bit of firmware to run the whole thing. I'm using a raspberry pi Pico to control the device. They're absurdly cheap ($5) and pretty easy to populate on the board since they're castellated. I'm planning to write the firmware in Ada, I'm curious about a lot of the safety features of the language and this seems like a good project to use it on. I'm hoping to use a tool called SPARK that's available with Ada. It lets you prove certain properties about your program, providing certain guarantees about its behaviour.
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Re: DIY Turbopump Controller

Post by Martin Fyhn »

Peter Schmelcher wrote: Sat Jan 23, 2021 4:19 pm Nicolas these are internal pics of my NT10 controller circuit board before I repaired it but after cleaning with compressed air. It had previously been repaired by someone and was sold "as is". Unfortunately, I never found any schematics so I repaired it using these pics.

The NT10 controller spins up the turbo in discrete drive frequency steps with coasting between frequency increases. During the coasting moments the voltage produced by the motor windings are measured and used as a tachometer reading. As I recall the turbo needs to spin up within 2 minutes getting quickly through a 50Krpm mechanical rotor resonance.

Today my plan B repair would be a new variable frequency drive for a CNC router spindle ($130). The faster VFDs run up to 1000 Hz and I suspect that with a crystal change hack one could increase the upper frequency.
-Peter
Hello Peter,

Would you happen to have some photos that are closer, and/or more in focus, of these boards?
My NT12, freshly bought from ebay, is host to quite a few glass diodes, that has turned an unhealthy shade of brown (it wasn't me... I promise... It was like that when I got it *furiously polishes halo, and ends up getting electrostatically shocked*... No seriously - I tore it apart before trying to power it, as I suspected that there could be issues. I'm in Europe, and bought it from another European country, and found the voltage-selector set to 110V. Also found a filtercap near the supply, that was ripe for creating some fireworks (it's missing on your photo - in case it was missing when you got it, and you want one installed - it's a 4n7 Y2 safety capacitor)). I've desoldered one of the roasted diodes to check if it's functional, which it is, but I'd like to replace them regardless, but I can't identify the things. I can say that the one I tested shows no signs of being a Zener, and has a voltage drop of .55V, which leads me to think that it's a Schottky, but that's as far as I can get, and it's one in roughly 26 ':D

I'd also be veeeeeeery happy with the diagrams - and have sent a request for them on the google drive link, but as I'm an impatient bugger, I'd be exceptionally happy if someone could provide me with some juicy diagrams for my lovely little inverter! :D
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Re: DIY Turbopump Controller

Post by Peter Schmelcher »

I had a look for other pics and I did not find any.

Rex combined the schematics that Jerry posted and using them you can repair the controller.
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Re: DIY Turbopump Controller

Post by Nicolas Krause »

Slowly plugging away at the firmware for the controller. Have been learning Ada, and I have a development environment setup using gdb on linux. It's the first time I've worked with a command line interface for programming so it's been a neat educational experience. I've got the LCD communicating with the RaspberryPi Pico at the moment! Lot's left to do but always a fun step.
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