Simple turbo pump controller

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Simple turbo pump controller

Postby Alexi » Thu Sep 02, 2010 2:09 am

The pump:

Recently we bought a couple of cheap TPH-055 turbo pumps from eBay (Item number: 370455353773). The motor in TPH-055 is single phase, two poles, permanent magnet; therefore the pump spins at the drive frequency. The winding is center-tapped, which makes it easy to drive it with only two transistors. I designed simple controller for those pumps.

The controller:

During powering up capacitor C4 resets D-trigger D2 and the red LED turns on (see the diagram). If signal from the Hall sensor (pin G) is high then transistor T1 turns on and current flows from the 28V power supply through 10 Ohm current limiting resistor and through A-B halve of the motor winding. If signal from the Hall sensor is low then T2 turns on and current flows through A-C halve of the motor winding. At this point the pump starts rotating and spins faster and faster.

Each falling edge of the Hall sensor signal triggers the 555 timer, which generates a single pulse. Each rising edge of the Hall sensor signal locks the state of 555 timer output in the trigger D2. When the halve-period of the sensor signal becomes shorter then duration of the pulse from timer, then the trigger D2 changes its state. Green LED turns on and both transistors remain off until halve-period again becomes longer then the timer pulse and the trigger changes its state back.

Normal speed of the TPH-055 turbo pump is 90 kRPM or 1500 Hz. The resistor R1 sets pump’s final speed. R1 should be either adjusted to make 333 microsecond pulses (halve-period of 1500Hz) at pin 3 of the 555 timer or could be set to turn on the green LED when the pump reaches desired frequency.

Testing:

The pump (right out of the box: no cleaning or oil change was done) was connected to the mechanical pump and to the small chamber with an ion gauge inside. The controller was assembled on a breadboard and the wires were connected to the pump with push-on connectors. The Hall sensor signal frequency was measured with a multimeter and an oscilloscope. After power-on the pump reached 1 kHz in about 5.5 minutes, and it took about 14 minutes to reach 1.5 kHz. The potentiometer R1 was adjusted to hold 1.5 kHz frequency. Pressure in the chamber at this point dropped down to 6e-6 torr. During a few days test run the frequency remained within +/- 1 Hz of 1.5 kHz, and the pressure in the chamber dropped another order of magnitude.

Alex
Attachments
TPH055 controller 017.jpg
TPH055 controller 017.jpg (886.51 KiB) Viewed 341 times
TPH055 controller 009.jpg
TPH055 controller 009.jpg (885.45 KiB) Viewed 341 times
TPH055 controller 003.jpg
TPH055 controller 003.jpg (910.78 KiB) Viewed 341 times
TPH055 controller 008.jpg
TPH055 controller 008.jpg (881.51 KiB) Viewed 341 times
TPH055 controller 004.jpg
TPH055 controller 004.jpg (889.33 KiB) Viewed 341 times
TPH055 controller 001.jpg
TPH055 controller 001.jpg (889.34 KiB) Viewed 341 times
TP controller diagram 1.PNG
TP controller diagram 1.PNG (142.09 KiB) Viewed 341 times
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Re: Simple turbo pump controller

Postby Carl Willis » Thu Sep 02, 2010 3:05 am

Brilliant addition! Thanks very much for this report. The TPH/TPU pumps are always on eBay at attractive prices, but seldom come with a controller. This kind of homebrewing might just revolutionize access to cheap turbo pumps for hobbyists.

-Carl
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Re: Simple turbo pump controller

Postby John Futter » Thu Sep 02, 2010 6:41 am

Alexi
Very good I think you can lose the series resistor or seriously reduce it and the unit will speed up faster.


For all the rest of you out there most turbos are three phase and I have made a universal controller to make them go. Because they are three phase the rotor tracks the drive signal and when nearly in sync the current drops dramatically details here http://www.coultersmithing.com/forums/viewtopic.php?f=12&t=83.
Note that two phase units do not have hard coupling and to know where the rotor is you have to use the inbuilt hall sensor or put one in yourself


Now there is a complete solution for all pumps out there orphaned from their controllers
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Re: Simple turbo pump controller

Postby DaveC » Thu Sep 02, 2010 7:03 pm

Alex -

Sweet! One of those things we all think about doing, "someday"... and you did it.

The small load of the little pumps, when finally at base pressures, means the drive hardware, doesn't have to be massive.

Nicely done. Thanks for sharing with us.

Dave Cooper
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Re: Simple turbo pump controller

Postby David D Speck MD » Thu Sep 02, 2010 7:58 pm

Alex,

Thanks for posting the controller schematic. Based on the ease of constructing this controller, I bought one of the pumps for myself and a friend.

Three questions:

Does the pump "know" how to always start up in the correct rotational direction? With only 2 phase drive, it seems like it could go either way, unless it had a shading coil built into the stator to insure proper rotation.

Do you have any info on proper lubrication and oil change procedures for the pump?

Do you have the designations for the pump flanges? All of my equipment is Conflat style, so I'll have to scare up a transition connector.

Thanks in advance.

Dave Speck
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Re: Simple turbo pump controller

Postby Chris Bradley » Fri Sep 03, 2010 12:56 am

Do these TPH pumps have a passive magnetic bearing (upper bearing)?
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Re: Simple turbo pump controller

Postby Alexi » Fri Sep 03, 2010 2:47 am

David,

The pump does "know" how to always start up in the correct rotational direction. Sense of rotation is determined by the phase relationship between the hall sensor signal and the current through the winding. If the hall signal and the current are in phase then the motor spins in one direction, if they are 180 degrees out of phase, then the motor spins in opposite direction. No shading coil is needed. If you switch wires B and C, then the pump will try to spin in the wrong direction. You can see how this type of motor works if you draw a picture of a magnet inside a coil and 90 degrees shifted hall sensor.
Obviously, there are two dead spots from which motor will not start: where the magnet is perfectly aligned with the coil’s axis. The pump is designed to always stop between those dead spots.

There is some info on lubrication, oil change and cleaning in the manual (attached).

The pump flanges are: DN 63 ISO-KF and DN 16 ISO-KF.

Chris,

Yes, those TPH pumps do have a passive magnetic bearing (upper bearing).

Alex
Attachments
tphu060.pdf
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Re: Simple turbo pump controller

Postby Chris Bradley » Fri Sep 03, 2010 9:19 am

I was wondering, though, whether that was an active magnetic bearing. I have a TPH (not sure of the number) and it has a zillion pins on it, so I figured those were some wonderfully over-complicated means for active control. I suppose if it has one fixed lower bearing, retaining it axially, then I guess that probably means the upper can be passive (I seem to recall that passive mag bearings can only retain in 2 axes).
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Re: Simple turbo pump controller

Postby chad ramey » Sat Sep 04, 2010 10:32 pm

To the people who ordered these and have already received one:
Did the pump come with the ISO centering ring that is pictured in the listing?

I bought one of the pumps and need to know if I need to buy a centering ring.

Thanks,
Cahd
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Re: Simple turbo pump controller

Postby richnormand » Sun Sep 05, 2010 12:52 am

"Did the pump come with the ISO centering ring that is pictured in the listing?"

Mine did not.
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