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Author: Subject: Homemade driver for turbomolecular pumps? (help needed)
Gooferking Science
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[*] posted on 29-9-2014 at 15:19
Homemade driver for turbomolecular pumps? (help needed)


I am going to be purchasing a turbomolecular pump for a project. Is it really necessary to purchase an expensive driver that works for that model, or can a driver for turbomolecular pumps be made by hand? I can find much on this subject on the internet, so I was wondering if any of you have some ideas. Any help is appreciated. FYI I am a complete noob with turbomolecular pumps. I have read quite a bit on them, but I am pretty sketchy when it comes to their operation.

[Edited on 29-9-2014 by Gooferking Science]

[Edited on 29-9-2014 by Gooferking Science]




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SimpleChemist-238
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[*] posted on 29-9-2014 at 17:30


is it for a fusor?
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SimpleChemist-238
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[*] posted on 29-9-2014 at 17:32


if you were tying to make a high vacuum I would be scared of implosion.
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Gooferking Science
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[*] posted on 29-9-2014 at 17:45


I know about vacuums and implosions. I have worked with vacuums quite a lot. Yes I am making a fusor.



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[*] posted on 30-9-2014 at 13:48


What do you need to Drive it ? Electronics ?

If it's just a high speed motor with some torque, use a hobby motor and driver (aka ESC).

www.hobbyking.com is really cheap.




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Lambda-Eyde
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[*] posted on 30-9-2014 at 14:33


I'm not an expert, but I'd say no. There's no chance you could make that without being very experienced with electronics. Turbomolecular vacuum pumps are finicky beasts that require very special start-up and shut-down procedures, for example. Accelerating the rotor to 30000 rpm is not something you do with the flick of a light switch. I have an Edwards EXT255Hi which costs in the range of thousands of dollars, and I bet there's a pretty good reason the controller costs the same amount of money.

Quote: Originally posted by SimpleChemist-238  
if you were tying to make a high vacuum I would be scared of implosion.

Why would you? The pressure difference between 10 torr and 10e-5 torr is absolutely nothing compared to the difference between atmospheric pressure and the pressure inside a filter flask.




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Gooferking Science
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[*] posted on 30-9-2014 at 16:49


So is there a "cheap" way to get the right equipment, say as used or surplus? Or should I explore other high vacuum methods?



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Lambda-Eyde
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[*] posted on 1-10-2014 at 06:02


Quote: Originally posted by Gooferking Science  
So is there a "cheap" way to get the right equipment, say as used or surplus? Or should I explore other high vacuum methods?

I got mine from a mass spectrometer. Which I found at the tip... :)

There are also other pumps that could be used.




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[*] posted on 1-10-2014 at 13:29


The one that we use on our SEM seems to increase speed in discrete steps as the chamber pumps down. I think the controller is monitoring the pressure inside the pump, and increasing the speed when appropriate.

Also, I was taught that if a turbomolecular pump is opened to the atmosphere while it is running at full speed, the pump can explode. Be careful.
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[*] posted on 1-10-2014 at 15:31


Can anyone explain what is Required please ?

So far it seems that a 'driver' is required (OP)

Many Warnings , yet few Solutions.

What, Exactly, is the Question ?




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Artemus Gordon
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[*] posted on 2-10-2014 at 15:40


Well, from looking up turbomolecular pumps, I have learned that they are turbines that need to be spun up to 70,000 rpm, and they cost a few thousand dollars, not including a driver. So, I assume it comes with a built-in motor, but the electronics to drive the motor cost extra.
It also appears the speed needs to be variable, based on the level of vacuum in the chamber. So, a vacuum sensor is needed and it has to control the driver circuit.
It would be easy to build a microcontroller circuit that could produce square waves at variable frequency up to 70 kHz. It could even produce multiphase pulses. And responding to a vacuum sensor would be simple, if a sensor with a digital output is available at the range of vacuum needed.
Then, you would need an analog circuit that could convert the square wave(s) to sine waves at the spec'ed voltage and current levels.

In conclusion, if you have access to all the motor specs, an appropriate vacuum sensor, familiarity with microcontrollers, and the requisite knowledge of analog circuits, plus a good knowledge of how the pump needs to spin up and spin down in a safe manner in response to the vacuum level, you could build a driver, and you might not destroy the pump and/or yourself, but I wouldn't bet on it.

Just buy the driver.
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