Turbomolecular pump troubleshooting (EXT255H with EXDC80)

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Chris Giles
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun,

I recommend that you get comfortable with how to measure voltage and current first and experiment with how the voltage and current limit settings work on your PSU(s). You can do this by using some resistors and experimenting with the PSU at low power, say < 10V and < 0.5A. This will be useful for you for other tasks as well.

As Rex points out, if you have put the meter *across* the PSU while measuring current, you have short circuited it! Whilst this will indeed test the current limit it is highly inadvisable especially with a cheap PSU and above a few volts. I don't think you will get any useful information using the DMM in min/max mode. To see the dynamic behaviour one would use a scope but that should not be necessary for this task.

If you tried the Turbo when the PSU was not shorted out, then I suspect that you have not satisfied whatever conditions are necessary to enable the motor drive. Your other measurements make it seem like it is in a standby state.

Regards
Chris
Arun Luthra
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

The linear DC supply arrived, but the problem remains. Everything is the same.

I will try the 10,000 uF, 100V-rated capacitor when it arrives in 48 hours.

In the meantime, I'll investigate potential issues like oil level.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

Hi Arun,

Can you explain how you are wiring the driver? Are you sure you are using the right pins with the correct input?
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Here is the pinout that I'm doing:
pins-labeled.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I'm pretty sure it's correct, but hopefully is something is wrong and it can be easily corrected.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

I may be wrong, but it seems that you have a problem on pin 2. I am not an expert, but I believe you should connect pin 2 to pin 5 and 6 (0V).
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Rex Allers »

Re pin 2:
Pin 2 should be an output (80% speed) which should not be needed, especially since he can't yet get the turbo spinning. Definitely, don't connect it to ground.

From the manual he linked, here is the pin-out description.

EXDC80 pins.png
I had looked at his earlier pics and thought the connections looked OK. The new closer detail pic seems to confirm.

As Arun said, the EXDC80 has a nine-pin connector. The other hook-up suggestion was for a 15-pin connector that seems to be for a different driver module.

Arun,

You never said anything about this new supply except that it is a linear bench supply. What is it? What voltage and current ratings? Is it still the input to your 80V booster card or does it make the 80V directly?

You never really seemed to indicate that you understood what we were saying about how to measure current.

For diagnosis, I hope you have or can get two meters to connect at the same time. One to measure voltage and one for current. Hook them up as in this diagram.

measure.png
Note that the amp meter is on a single wire between the supply (+) output and the driver input. Don't split into two wires on pins 7 & 8 until after the ammeter.

Record the values with the start/stop switch open (stopped), then record again closed (run).

The manual says max running current should be 1.1 A. They don't say what it should be stopped (switch open) but I would expect it to be low, probably less than 0.1 A.
Rex Allers
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

It isn't super clear in the instructions, but I believe TMP normal status on pin 2 is a passive voltage used for reporting info and for driving an optional relay.

Note how for pin 1 , it says "close w.r.t. pins 5 and 6" whereas for pin 2, it says "closeD w.r.t. pins 5 and 6". "Closed" with a d on the end.
tmp-normal-status.jpg
tmp-normal-status-2.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I added the the 10,000 uF capacitor. It is polarized, so negative goes on the negative terminal. It drank electrons for a few seconds to fill up, then I switched on the turbopump but it is still not working, the same as before.

I emailed Edwards yesterday, even though I should have done that days ago. I'm not sure if they will reply without a support contract. Of course I am not the original owner.

Edit: better image
intput-filter-ac-dc.jpg
Last edited by Arun Luthra on Thu Sep 19, 2019 10:32 pm, edited 1 time in total.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

It is a linear bench DC supply, max 30V and 5A. It is feeding a DC to DC booster that upconverts 30V from the DC supply to 80 V out of the booster.

I recall how to measure current now.

I don't have a second meter at the moment but I can tell you that the DC supply reports 0.2A draw and about 6.5W.

I set a current limit on the DC supply as high as 4.5A without success.
Chris Giles
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun,

please connect your DMM as shown in Rex's diagram and report back what you measure. This is the Output of your DC-DC converter. If you only have one DMM, then you can measure the voltage and current in two separate tests. Leave pin 2 disconnected.

Also can you draw a schematic diagram that shows it exactly as you have it connected - i.e. like Rex's diagram but expanding the "80V PSU" box to show how you have connected the 2 power devices. Please show where the lines marked 0V and GND in the photo are connected. Pin 3 is the chassis ground which you must connect to the mains earth, i.e. the centre pin of your AC wall socket. Pin 5,6 must go to the -ve o/p of your DC-DC converter not the 30V PSU (although you could connect these together).

If you have connected a cap over the 80V output please ensure it is at least 80V rated (100V is a common rating). Anyway, for now just remove it. That is not going to be the cause of your current problem and it could cause you danger from a shock as it may hold charge for a while - 80V may be enough to give you a kick.

Best regards
Chris
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Artem Artemov
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Artem Artemov »

I have such pump, but on 24 volts. Works without problems. Try another connection.
AAB37669-B55D-4E52-8B85-C3BC6D392DEC.jpeg
E9249373-8001-49D4-8AED-94A01CBA5939.jpeg
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Artem Artemov
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Artem Artemov »

41AC0BD4-DAF1-4156-8BCC-0B28DDA0AB6D.jpeg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Cristiano_Machado »

Artem, I also have this pump and I suggested to connect pin 2 to pin 5 and 6. I agree with you that this will correct the problem.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Do you have a version of the instructions where it says to connect pin 2 to 5 and 6 on the EXDC80, 9 pin 80V unit?

The negative (-) on the booster is about 2V different from ground. Does this matter?

I did some load tests on the DC Booster output:

- With a total resistance of 75 ohm in wire wound resistors, it supplied the specified 80.0V, while 1.067A went through the resistors for a power of 86.4W. The DC supply was set to 30V output, had 3.08A and 92.3W. (Efficiency about 93.6%).

- With 50 ohm in wire wound resistors, the expected wattage was 128W through the resistors, however the DC booster was not able to provide 80V.
- When the DC supply was set to 19V, it went into current limit mode, using 94.6W at 5A. The booster limited itself to 65V and had 1.32A. (Current limited at 19V and higher on DC supply.)
- When the DC supply was set to 18V, it was not current limited, it used 84W and 4.68A. Of course the booster could not sustain 80V here either, it was at 61.8V and supplied 1.24V (76.6W).

The EXDC80 is supposed to take 70V-85V, and it says 93W on the label. That implies 1.16A and 69.0 ohm at 80V.

Somewhere in between 50 ohm and 75 ohm, the system is not able to provide 80V output... the EXDC80 does fall in that range, but closer to the 75 ohm end...
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

exdc80-diagram.png
Pin 2 is connected to optional DC relay (item 4) and optional relay power supply (item 5). If these items are supposed to be replaced with uninterrupted wires, then it would connect directly to pins 5 and 6... it's not completely crazy?
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

I just tried connecting pin 2 to the negative on the booster, but it had no effect (no change).
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Rex Allers »

Arun,

Pretty good job measuring V and I for a couple resistors. Now throw the turbo out and just run the resistors! They're fairly dependable.

What I am trying to say is ** Why didn't you give us V and I measurements for the controller as the load, trying to run the turbo? ** That's what matters.

So cantcha please do that, for start-switch open and then for start-switch closed. Also it would be easier for you and less possibility of any problem if you can get another meter to get both V and I at the same time.

Sounds like your present meter is good for amps with some protection. For V any basic DMM that can measure, say 0 to 100 VDC should be fine, like the old freebe Harbor Freight meters. Tons of them from internet sellers or you could probably find one locally - tool store, auto parts.

If you can't or won't get a second meter go ahead and give us the actual controller-loaded readings from 4 iterations.
(2 measurements: 0n and 0ff switch, with 2 meters)
(4 measurements for: 0n and 0ff switch, with 1 meter)

--------
The Pin 2 suggestions continue?

You and I both posted the tables from the manual pages. Unless that's the wrong manual, pin 2 is an output that changes state when the turbo spins up to cross 80% of full rotation speed. Essentially it is pulled up to 15 V while below 80% and switches (connects) to ground (pins 5&6) when above 80%. From your last circuit connections diagram: #4 is a DC supply for a relay (say 5V), #4 is the coil of the relay ; when pin 2 switches to ground at 80% speed the relay closes.

Sounds like you could just monitor the voltage on pin 2 for the 80% crossover without an external supply and relay. But...

Anyway, I still think, just ignore pin 2 for now. Let it float.
Rex Allers
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun

use your voltmeter to monitor the PSU voltage, i.e. between pin 6, 7. See if it dips noticeably below 80V when you press the start switch. Looks like your PSU is working OK according to your tests. The manual says max current is 1.1A, which could well be when it is first energised. If it is cutting out at startup due to the PSU not being able to supply enough current then you should at least notice the turbo spin up momentarily and then shutoff. Are you sure you have the pins numbered correctly? You could check with your DMM on resistance/continuity that pin3 is connected to the metal case or the cable screen, and that pin 5,6 are connected internally, likewise pins 7, 8.

Regards
Chris
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

The resistors provided valuable information about the load-bearing capacity.

When the power supply is on, there is 0.07 amps flowing through the booster positive terminal (+). There is no change in this current when the switch is turned on or off.

The voltage across the positive and negative terminal on the booster remains stable at 80.0V whether the switch is on or off. The multimeter does not detect anything above 80.0V in max/min mode when the power supply is turned on, or when the pin 1 switch is turned on.

Like I said before, the DC supply is supplying about 7 watts whether the pin 1 switch is open or closed.

The voltage between pin 5 and 7 is 80V. Between pin 6 and 8 is 80V. Between 7 and 8 is 0V. Between 5 and 6 is 0V.

NOT SHOWN ON DIAGRAM: The DC supply ground pin is connected to the ground post on the pump. This is the same ground connected to pin 3.

I got a $40 oscilloscope and will try more to freeze-frame the turn on curve. I already saw some smooth turn-ons, which is expected because it has capacitors. There is a youtube video with a very similar looking 600W booster, and he did not detect any turn-on voltage spike either, but he was only using a DMM in max/min mode to detect a spike.

As mentioned, there is about 2V difference between the ground pin and the negative pole on the booster. I am not sure if it matters. Maybe the ground pin on the power supply does not have a good enough (low resistance) connection to ground.

Here is the circuit diagram:
circuit.jpg
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Chris Giles »

Hi Arun,

that all sounds good. Are you sure that you have the pinout correct? For instance, try the 2 checks i mentioned before.

regards
Chris
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by rhorst »

Looking at the photo of your power supply, it looks like it is connected incorrectly. That type of supply has floating + and - connections and a separate ground internally tied to the chassis but not to either voltage. You probably do not need any ground connection at all, but definitely need both + and - tied to whatever you are powering. Often, the negative and ground are externally strapped together because most devices use positive voltages for power and control.

You probably want to tie the negative and GND together and to the negative of the booster supply, and then tie the positive from the supply to the positive of the booster.

Without the negative terminal connection, you might be reading some correct voltages because leakage brings the negative terminal to the same potential as ground, but without that connection, it cannot deliver much current.
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Rex Allers »

I don't think we've seen a pic of connections since he got a different linear supply but I suspect it is ok. The DC-DC booster card is making 80 V out, so must have a reasonable input. All earlier pics seem to show a proper connection to the supply.

Have you ohmed the start switch to verify open/closed is good?

As Chris said, the measurements seem reasonable.

Arun, I think you said you got another of some portion of the turbo hardware. Was it the driver module, the turbo, or both?

I'm not seeing anything wrong in the configuration, except not working. When start is closed, I would expect current to jump up around the specified 1.1 A. That's from the 80 supply, the current from the 1st supply should jump up too but not the same amps as the 80 V load.
Rex Allers
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by John Futter »

rhorst
please follow the board rules re name convention and posting rules
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Re: Turbomolecular pump troubleshooting (EXT255H with EXDC80)

Post by Arun Luthra »

Thank you for your patience everyone. It turns out it was a bad CABLE. (female to female DB-9 cable connecting the EXDC80 drive module and breakout/pinout board).

It spins up beautifully now.
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