Page 2 of 6

Re: Simple turbo pump controller

Posted: Sun Sep 05, 2010 12:59 am
by chad ramey
Thanks, I'll go ahead and order one from lesker. Have you been able to test your's yet?

Re: Simple turbo pump controller

Posted: Sun Sep 05, 2010 8:13 pm
by richnormand
Not really. Got it to turn with a two-phase sine signal from my audio generator into a 100W strereo amplifier as a quick test after downloading the specs sheet. I got the vacuum chamber and coupling from e-bay during the summer. Already have the backup pump. Now waiting for some SS hoses and two KF25 valves. All the stuff is in a box at this time. The "honey-do" list takes priority..... Please post cost and ## for the ring once you find it.
Cheers and thanks.

Re: Simple turbo pump controller

Posted: Mon Sep 06, 2010 12:09 am
by chad ramey
Thanks for the information. Sounds promising, I wish you the best of luck with getting it running. I have full intentions of having mine running on my reactor by the third weekend of september (hopefully earlier than thst).

I have the ISO63 centering rings on several sites:
Lesker- ... fm?pgid=al
LDS Vacuum Shopper-
MDC- ... ay?1.a.1.m

I'm going to talk to a friend at Quintronix tomorrow to see if they have any available, and if they do I'll let you know.


Re: Simple turbo pump controller

Posted: Wed Jan 05, 2011 5:35 pm
by DSchultz
I found a surplus source for the RFP2N08L FETs. I need to buy 20 of them to make the minimum order. Does anybody else need these FETs or have you all found some other FET that works as well without being un-obtanium?

I am going through Amphenol and ITT Cannon catalogs to try to identify the power connector. No Luck so far.

Re: Simple turbo pump controller

Posted: Wed Jan 05, 2011 7:04 pm
by richnormand
Hi Dan.

You might be interested at the NTE line of substitutes. They list the NTE2382 as a replacement for both the RFP2N08 and the RFP2N10.... The specs are identical except for a 100V rating instead of 80. I ordered 5 NTE2382 from Allied Electronics ( $3.95 CAD each) since they were in stock. No min orders either. They have been working for almost one month and no issues. The NTE line is very popular for all sorts of repairs and it has a very extensive range of "equivalent" components. Most local electronics repair stores will carry them but they are slightly more expensive than ordering the exact part (if still available) from the large outfits such as Mouser, Allied, Digikey and such.

I initially replaced the 555 with a phase locked loop for smoother transitions and went back to the original 555 as there were no real improvement. I did add a switched selection of both full speed and standby (60%), each with its own 10 turn pot. Also for about $12 on eBay I got a small four-digit display frequency module. This gives me the rotational speed, 1500 Hz full and 900Hz standby. I can now follow the pump in ramp up or down to a full stop.

For power a 24V OEM surplus supply can be internally (mis)adjusted to provide the 28V. I included a separate switch for that too. This allows keeping the 5V to the logic electronics during ramp down. The motor back emf at full speed will heat the MOSFETs too much unless you keep the 5V alive to keep switching (with the 28V off).

Finally I noticed that in very rare cases the pump will not start and one FET is full on and the other full off. Not a good scenario. A small twist of the pump or a restart will cure that. I guess the rotor can stop in a no-man-land position. The freq display solves that issue since I can immediately see the startup upon switching the 28V on. If it stays static it is just a matter of turning it off and reset the 5V and then the 28V.

As far as the connector is concerned I ended up soldering a wire to each pin and fan them to a strip junction block with a label for each function. Nice that the full specs for the pump are available online too.

By the way I am not using the fan that came with the pumps either. They both barely get warm after several hours of running. Maybe if I flow lots of gas through them.... but that is for later.

EDIT: See note by Alexi further down in the posts about the difference between the RFP2N08 and the RFP2N08L. The NTE sub does work well for me however.

Re: Simple turbo pump controller

Posted: Thu Jan 06, 2011 1:00 pm
by DSchultz
I had a negative experience several years ago with a NTE "universal replacement" FET which was not so equivalent. Since then I try to find the original part whenever possible. I have too many projects going than to try to re-engineer what others have already proven to work.

What are you using for a power connector? Do you just push the wires onto the pins one at a time?


Re: Simple turbo pump controller

Posted: Thu Jan 06, 2011 2:29 pm
by richnormand
I agree with you Dan,

Note that I used "equivalent" in quotation (as with a big grain of salt) as YMMV but for this applications they seem to work for me and others may find the NTEs easier to obtain than chasing the exact part. Been using the substitutes for more than 30 years now from the time they were RCA SK series, Sylvania ECG subs and now NTE and, yes, you need some creative empathy from time to time as they are not the real McCoy. Initially made for people fixing TVs and such at the time.

I always try to find the exact match when possible too. However a friend of mine that is in the electronic component failure analysis and counterfeit or rebranded detection business has a mitigated opinion about getting components from non-authorized dealers, in particular resellers of older parts no longer available. What you see may not be what you think you have. Not much of an issue here but not funny in medical, aerospace or other safety related applications. That being said, I have used resellers of obsolete or hard-to--get components several times with great success. It all depends on the price and minimum order. Or... how desperate I was to get the part vs redesigning the whole mess with modern components!

For the connector I simply tinned the end of the wires and tinned each individual pin on the pump connector. Laid the two side by side and I then wetted each together one by one and heatshrinked each and then the lot together with an RTV silicone core. Dont overheat as I did not check how the wires are attached to the pins inside the pump body. Quite sturdy and easy to dismantle when or if I manage to find the mating connector at a decent price. I have two other pumps as spares. Did not want to invest much money until I got a feel. I will next change the oil wick but these look like they were an excellent deal.


Re: Simple turbo pump controller

Posted: Fri Jan 07, 2011 10:20 pm
by gpecke
Dear Alexi,

Thank you very much for your post. I have bought two pumps on the strength of your information.

I am glad you mentioned the fine black muck, which needed very careful removal.

I have already bought two Alcatel/Adixen MDP 5011pumps, also from E-Bay. These work very well. I have posted some details on how to drive them, and will try the TPH055 on the same inverter. The motor is very similar in principle to that of the TPH055, except it has no winding center-tap, so your simple inverter would not work without an external transformer.

The MDP pumps have a much lower rate , but a much higher ratio and exhaust pressure. I will try using one as a clean scavenger and fore-pump to the TPH055, and hopefully retire my noxious Hg vapor pump, cooling water and cold traps once and for all.

Re: Simple turbo pump controller

Posted: Sun Jan 09, 2011 8:49 pm
by Alexi

There is big difference between the RFP2N08L and RFP2N08 transistors. The L sands for "use with logic level driving sources". The RFP2N08L can provide 2-3 amps drain current at 4V gate voltage and the RFP2N08 - only 0.1-0.3 amps.

Any transistor, which can provide at least 2 amps drain current at 4V gate voltage, will work fine in my controller circuit.


Re: Simple turbo pump controller

Posted: Sun Jan 09, 2011 9:14 pm
by richnormand
Hi Alexi,

first of all many thanks for posting the circuit.

As mentionned in my previous post the only mods that I did (after trying the PLL and such) was to add a full speed and a standby mode switch. I am now waiting for a cheap 4 digit frequency counter (eBay $12) to monitor the pump speed. I was using my good HP frequency meter not only the adjust the pots but to monitor the pump so I figured it would be a good addition.

Here is the spec sheet of the NTE MOSFETs I have been using for over a month. Rock solid, no issues. Looks like they meet the L specs OK. There were cheap and in stock at Allied Electronics.

Looking at your photos: does your pump need the fan? Mine stays cool in the test setup so I removed it.

Best wishes for the New Year.

Edit1: You are right of course about the difference between the two types. Interesting thing is the search software for NTE does not list the L variant in my software version.
Edit2: here is a pix of the setup. The empty space on the board is for the freq module.
Edit3: I did add a note to my original post pointing to your post about the L variant difference. Thanks for catching that.