USB dropping out when roll off roof opens and closes

[Paul Haese]

I have discovered a unique problem that I cannot seem to nut out myself. I have sought help from a couple of guys I know that a handy with electronics and electrics and it has stumped them too. I did get plenty of good suggestions from them but I thought I would put this out for people who might know how to sort this.

The problem:

When I connect up CCDautopilot which connects my mount (the sky6), maxim (controls the camera and guiding), Focusmax (focusing), pinpoint (plate solving), AAG cloud sensor (weather), rotator (Pyxis) and the scope dome driver (the roll off roof), everything is fine. Then when I open the roof via run imaging session; about 15 seconds into the roof opening the main camera (QSI) disconnects and makes Maxim hang, that caused all sorts of havoc. I need to reboot the entire system to get everything working again.

Now just to let you know the cameras (both guide camera and QSI), Focus (robofocus), dew heater and rotator run off the mount hub pro, which is powered by a 20amp 13.8v regulated power supply sold at Jaycar.

The roof is powered by a power cable coming out of the power point into the hardware USB card.

Scope dome do say to use heavily shielded USB cables as the system can produce some problems with cheap USB cables. I have good cables but not perhaps heavy shielded ones.

To test things out I have left the roof off the connect with CCDautopilot and opened that separately. It still did the same thing. I have even totally disconnected the USB cable that connects the roof hardware to the computer (removed the USB cable altogether) and when I open the roof or close it the camera disconnects and hangs maxim (no matter whether it is connected to CCDautopilot, or not).

I have not yet powered the Mount hub pro on a separate power system, from say the house or a battery. That would tell me whether the regulated power supply is at fault.

I have bought heavy duty double shielded cables from Lindy.com.au which should arrive next week. That may stop the problem although I doubt it.

I have opened the roof first then started the computer and all the appliances and things seemed ok, although I cannot tell about a full run yet.

The roof has an inverter than converts the 240 power to 0.9kw for a three phase motor. I have used a wiring loom that was supplied by the manufacturer of the scope dome gear and it acts exactly like the loom I had done myself before they sent me the plug and play one. So I don't think that is the problem.

To me this seems like a voltage spike or drop but I know there might be some other explanation. Feel free to ask me any questions you may have and I will answer those as best as possible. I really need to have the whole system connected.

Officially stumped????

[h0ughy]

well if plugged into a hub you have only a couple of amps available and everything adds up if powered by the hub? I have found that externally powered devices even though connected to the hub suffer similar Bermuda triangle effect - and things in a certain order. it only takes a few half amps inputs to add up to hub fully saturated then you just need that final push over and the serial chain is broken. in the end I had two completely different systems, dome and guide camera on one and then the imaging camera on the other. just my thoughts. you could even get a voltage drop, though how you would be able to measure that would be interesting? the longer the usb cable the tighter the power requirements as it drops down significantly

[mithrandir]

Paul, a couple of thoughts.
Does the motor cause a brownout that would upset the power supply and the stuff hung off it? You'd need something like an oscilloscope to pick up the transients.
Can you shield the motor and its cables? Why blame the USB if it's the motor's fault.

Your load on the power supply should be OK.

Running the motor from another power point might work, but off a different circuit would be better. If you have more than one phase, putting them on different ones would be even better.

[jase]

What happens when you change the main imaging camera (QSI) to the ASCOM camera simulator. Do you still get Maxim hanging when you try reproduce the problem?

[Paul Haese]

I also forgot to mention I powered the camera with its native power supply too and got the same results. So it is unlikely to be the hub, those hubs are made for this sort of work.




Yes this is my main leaning at this stage. I will test the system by powering from another circuit and then if that prevents the problem, then I will be digging another trench and that was hard the first time.

I had thought that getting heavier USB would do the shielding I need. Perhaps I am wrong here.





Not tried this but I suspect it is not going to help. I have noted that if I pull the USB cable I can disconnect the camera in Maxim and then reconnect. If I try to disconnect the camera without physically pulling the USB then it just hangs further. Worth a try though.

[Joshua Bunn]

Paul,
I connect all my gear to a powered usb hub and i found that when my SBIG camera was powered up (which i purposely restricted the power to), it initiated my mirror heaters to stop writing to my usb port. I then supplied the correct power to the camera and then connecting the camera had no effect on the mirror heaters.

my point... maybe its a power issue, but your gear sounds pretty good.

Also make sure you don't exceed the usb cable length or if so, use active repeaters, but im sure you know this.

Try going back to real basics and getting one thing to work at a time to issolate components, then adding one thing after another to try and find the issue.

Josh

[DannyV]

I powered my hubs via 12v to 5v converters powered from my 12v battery supply, rather than the 240v supply. This stopped a lot of hangups.

[DannyV]

Paul,
Have you seen these:
http://www.keterex.com/kxusb150.php
http://electronics-shop.dk/galvanically_usb_isolation.htm?curr ency=EUR

They might help

[Tandum]

I agree. Something is getting back into the usb and hanging the camera which freezes maxim and screws the goose. It's a pig of a thing to find. If usb devices disconnect they will not automagically reconnect when they reappear, you have to physically unplug and replug it so it cames back to the fold. Bring back serial I recon.

I had sort of similar issues which ended up being the qhy5L2 camera didn't like my usb card in the PC. Works fine when plugged into a usb port on the PC motherboard but would randomly disconnect from the usb card? The SX wheel will not work unless cabled directly to a PC. It just will not work through any hub.

You need to find these idiosyncrasies in your setup.

Good Luck.

[Bassnut]

Get a USB to USB opto isolator. You should do this anyway, asking for trouble if you dont.

[gary]

Paul, is the frame of the motor happened to be attached to the steel frame of the observatory?

Best Regards

Gary

[rally]

I fear the title of this thread might be confusing the diagnosis issue.

It may or may not have anything to do with USB - that hasnt been established yet.

It may well be software Driver problems, ASCOM problems, OS systems, Hardware problems

There are a lot of issues at hand here - its a complex system - hardware, firmware, many different circuits, many different devices all talking with one another, power supplies, motors, inverters, wireless systems, communications systems and protocols etc etc

This problem is occurring when the ScopeDome USB cable is not plugged in at all and there i sno connection to it and the PC or the rest of the system !
Therefore it has nothing to do with a direct USB problem - at least on the part of the ScopeDome controller, but may have something to do with an indirect consequence on the QSI USB side or elsewhere in the USB hubs and or their power supplies.

The wireless Scopedome controller is communicating to itself
(two halves - one on the controller side and one on the motor side) wirelessly when the Shutter is opening or closing and also when the limit switches open and close. The motor is a 3 phase inverter frequency controlled motor so we can't discount RF or electrical interference - although I would think this to be unlikely - something is causing the problem !

He has blown up one single phase to 3 phase inverter on the low voltage control side, so an electrical problem that is on the controller side cannot be eliminated.
And its unknown if there was any further damage when this occurred or from my perspective how and why it occurred, given it was tested beforehand.

So that leaves the possibility of a power supply or supply interference problem as well as a potential electronics circuit problem.

Paul says the error occurs when he uses the controller manually - 100% of the time, so its a very reproducible problem.
So the manually operated hand controller for motor control (without any connection of the ScopeDome controller via USB to the system) causes this problem in another electronic system entirely that is not connected except via the mains power. Note - this is still making use of the wireless comms link.

Paul is using CCDAutopilot, TheSky, MaxIm, QSI, FocusMax, etc etc and these are all talking via ASCOM and their various drivers.
So its also possible that there is an ASCOM Hub or driver related problem (that may or may not have its cause rooted in the USB system), but that would still need to be triggered off by the roof opening or closing activation - either motors or sensors or control circuit or frequency 1~ to 3~inverter.

I have suggested a few things for him to try to see if he can get a change :
Swap his imaging/camera system over to a 12v battery to eliminate the possibility of a main power or mains cabling interference between the roof automation system and his normal imaging system
To manually hold the limit switches in their same position initially so as not to trigger any further sensor activity and see if it still occurs - to isolate if its a wireless (or electrical) control problem related to the position sensors.
To shield the inverter output cables with some foil to see if that makes any difference
To avoid any looped cables - eg USB cables bundled up
To remove the USB hub (MountHubPro) out of the equation to see if that makes any difference - eg it could be resetting itself or doping something unusual when the motors are activated
Disable any other WiFi devices he may be using - that would include Bluetooth devices, USB wifi dongles etc - who knows a Blutooth Keyboard or mouse might be misbehaving !


I would add to those now -
Manually trigger the Inverter input for Forward and Reverse operation by manually Jumpering P1 and then separately P2 to Common (while holding the sensor limit switch in its same position as the roof moves)
To see if that triggers the errors - this eliminates the wireless communications system from the system and would imply an inverter/motor problem if it still remained - that ought to be overcome by most modern power supplies in the rest of his system.

If this didn't resolve things then as suggested I would be putting an Oscilloscope with event triggering - on the mains, the control circuit wiring, all USB wiring and all the power supply outputs of all devices to see if there are an obvious problems.

The fact that the problem is so absolute and repeatable and is not intermittent should make it a relatively easy problem to resolve or at least isolate further.

Hope that helps

Cheers

Rally

[gary]

Hi Rally,

These particular sentences are an important clue. Do you happen to know if the
frame of the motor is attached to the metal frame of the observatory?

Best regards

Gary

[rally]

Gary,

I dont know the answer to that question.

Whilst I have seen it superficially, I haven't inspected it as I wasn't aware of these problems then.
The motor is 3 phase, so none of the phases should be connected to earth and Neutral isn't required.
All of the three phases ought to be fully isolated from everything else electrically too via the single phase to 3 phase inverter.

But checking for stray leakage/loops is definitely warranted given the problem.

Cheers

Rally

[coldlegs]

Paul
My money is on earth loops between your PC and everything else. Have similar usb dropouts myself depending on the wiring configuration. Wire a few earths together and see what happens.
Cheers
Stephen

[gary]

Hi Rally,

Parasitic capacitance between the rotor and stator will allow for common-mode
currents to pass into the motor frame and if that is mounted on some other
metal structure into that too.

As the inverter will have high frequency spectral components, they will
be transferred via common-mode too.

Those noise currents will certainly play havoc with other electronic equipment within
the observatory and it is not surprising that something like a USB connection
would drop out.

So based on the description, none of this surprises or puzzles me.

Though one might potentially solve the particular problem at hand by opto-isolation
on all the other victim USB links, that tends to be the "Little Dutch Boy" approach
to the problem. The best prescription would be to solve it at the source by
installing common-mode chokes on the motor drive cables.

As few of these problems tend to fit into the realm of lumped circuit theory,
multimeters and oscilloscopes tend to be of little help. Instead, they are often
best diagnosed in the frequency domain and a spectrum analyzer and current
probe would be the first tools to reach for. However, hopefully none of that
heavy artillery will be called for and simply instaling the common-mode chokes will
solve the problem.

Best regards

Gary Kopff
Mount Kuring-Gai
02 9457-9049

[gary]

Hi Stephen,

That is the last thing you want to do! :)

All the best

Gary

[Paul Haese]

Hey thanks guys for the questions and detailed responses.

Good thinking Rally, I will see if that makes any difference although if I hard wire to the wireless unit this should sort the problem out. The previous inverter might have been checked but I doubt having an earth leakage problem would cause the inverter to be blown by me. To that end though I know have the scope dome plug and play kit installed and all seems to work until we go with full automation. Anyway, some more things to sort. Appreciate the advice.

Gary to answer your question re the steel frame work. Definitely not screwed to frame, but I will check just in case. I am pretty certain it is not but will do that anyway. When I screwed the motor on I took special care not to screw to the frame. That being the case though each wall frame is isolated by a timber post in the corners and the timber floor on which it is fixed. I wonder though could this be like a faraday cage?

The USB suppressors are a good idea anyway and I will pick some up. Is this what you mean by current choke?

I can say with absolute certainty though that I have all the earths sorted in the wiring of the observatory and all actives and neutrals are going to the correct places.

Really appreciate the advice and will do some testing with the ideas suggested so far. I will get back to you with further developments.

[gary]

Hi Paul,

With regards the motor frame not being attached to the steel frame, very good.

Nevertheless, it still has a very strong possibility of being noise related and
the cables from the inverter to the motor are likely to be the major source of it.

What are termed "stray" capacitances which cause leakage currents can
come from a variety of sources, including from the cables themselves,
the inverter, the rectifier within the inverter and so on.

To make this concrete, these stray capacitances are created whenever two
conductors are at different potentials and are separated by a, typically thin,
insulator. That dielectric might be, for example, just plastic or even just air.

As the voltages in the motor drive cables change very rapidly, these capacitances
allow tiny currents to pass through them and their paths back to their
the source may take some large physical loop area. A conductor having a large
loop area with alternating currents, even small ones, will generate electromagnetic
noise.

In order to improve the quality of the current waveforms in motor drive systems,
high frequency switching tends to be used these days. It is the very short
rise time of the pulses of this fast switching that is one major noise culprit and
not just the pulse frequency itself. These fast rise times are harmonically rich
which means lots of noise over a wide spectrum. This multiplies the probability that
some other circuit will be susceptible to noise at one of those frequencies.

There are sources of noise and then there are victim circuits. If the ends justifies
the means, one can attempt to filter the victims. The suggestion of isolators on
your USB connections is one approach to this in that if there are common-mode
currents passing back through these cables that had originated from the motor
drive system, then isolators block this return current path.

However, my suggestion is that if indeed the problem turns out to be noise
from the motor drive, then it can be wiser to cure it at the source. This then
minimizes the chance of the problem manifesting itself in some other way,
say noise artifacts on your images.

So the common mode choke, which is a form of transformer, goes on the three
cables from your inverter to the three-phase motor. Hopefully it will "choke"
one of the largest noise contributors.


Here is an example of a class of commercial three phase filters -
http://www.digikey.com/product-highlights/us/en/schaffner-three-phase-filters/1955
Here is a datasheet for one -
http://www.schaffner.com/en/products/datasheet-low-res/product/fn-351-general-purpose-emcemi-filter-for-three-phase-applications.html

For belts and braces, one could add current mode choke/filter to the source and
an USB isolator on the USB cable but I would start with the choke first.

As we just discussed on the telephone, also make sure any cables running
large switching currents are not in close physical proximity to, for example, the
USB cables. Even when run at right angles to each other, there may be sufficient
coupling between them to induce noise. The USB cables should be shielded
and the design of the shield and the equipment should be such that the shields
are fully connected to the chassis at both ends, 360 degrees around.

It seems telling that when you manually switch on the motor that the problem
manifests itself. Electromagnetic interference (EMI) problems
related to inverters controlling three phase motors are common
enough that they appear in the standard texts and in the literature.

It is important to appreciate that the path of interference can be both through
conducted noise and through antenna mode radiation. In both cases, the
choke/filter can assist.

Having said all of the above, it might be a power integrity issue with the
motor/inverter drawing large currents particularly when they first switch, but
I'd still try the common mode choke/filter first.

Best Regards

Gary Kopff
02 9457 9049

[gary]

Hi Paul,

With regards the inverter used to control the motor on the shutter, does it happen to be
SV008iC5-1F manufactured by LS or is it a SV iE5 or some other make/model number?

Best Regards

Gary

[Paul Haese]

Hi Gary, it is a LS SViE5. Why?

[gary]

Hi Paul,

Just have to duck out right now for a few hours so I will respond more fully
tomorrow.

Do you happen to know if the loom from the inverter to the motor uses shielded cable?

Best Regards

Gary

[Paul Haese]

I would say no. It is 6mm cable 5 wire loom cable supplied by scope dome.

The cable is plastic coated only with outer casing and inner casings.

[tlgerdes]

I remember year ago working with Barry to solve a noise related problem at one of my customers, similar thing, turn device A on device B stops working, device A and B not related.

Worked out that we a had a noise frequency harmonic in the power at some 19kHz when device A turned on, device B was running a data rate of 19200bps. Turning on device A was corrupting data on device B.

When we looked at the power with an oscilloscope we saw lots of noise harmonics at different at frequency mulitples from this device.

[Paul Haese]

Some developments - today I tested a few things out. I ran the camera and Mount Hub Pro (MHP) on a battery and the problem still happened.

I replaced the existing cabling with a shielded power cable. Shielding not connected to anything. Not sure where to connect that. Camera still dropping out.

Then I ran the STL11000 and nothing happened. No drop out at all. Roof opening and shutting with no issues. This confirmed it had to be the camera and its USB connection.

I then replaced the MHP with my spare and this did the same thing with both cameras ie QSI dropping out and STL11000 not dropping out. Now I knew it must be the MHP not being able to supply enough power to its USB's or to power the camera.

So I remove the QSI from the MHP and provide the QSI with its own power and USB. It works without drop out. All the other gear is still connected to the MHP. Nothing drops out.

So it appears that I need to take all the scopes off the mount and put in another USB cable through the mount and provide power in the same manner to power the camera. Further testing will identify any further issues. So it seems that in the end it is the regulated power supply suffering from a slight voltage drop when the roof opens and this affects the power to the MHP and that in turn affects the camera and forces it to drop out.

Anything else I should check?

[gary]

Hi Paul,

The reason I asked about the model of inverter and whether the cable from the inverter
to the motor was shielded was because I had been thinking about your problem,
looked at the schematics from the ScopeDome web site, saw what models of
inverters they were using and then hunted down the User Manuals for them.

Here is a link to a web site in South Africa that happens to have a User Manual
for the SV-iE5.

http://www.google.com.au/url?sa=t&rct=j&q=sv%20ie5%20manual&source=web&cd=1&cad=rja&ved=0CCoQFjAA&url=http%3A%2F%2Fwww.anadigi.co.za% 2Fproducts%2Fls-industrial%2Fvsd%2Fitem%2Fdownload% 2F114_a878506f94aee118b5bf4ff3a67bd 5ae&ei=Vzv2UY2XAoHbkAX53IDgCg&usg=AFQjCNGQzsDPhTfKKvYyi_L-UJdLAvBhAg&bvm=bv.49784469,d.dGI

You might like to confirm that this is the same model as yours.

If you could please turn to page 121 of 127 of the User Manual, I will attempt to
take you through it step by step.

On page 121 of the PDF, the manufacturer has their signed Declaration of Conformity
that they comply with EN 61800-3:2004 which is a standard addressing the
electromagnetic conformance (EMC) requirements of electrical power drive systems
and to EN 50178:1997, which is a standard addressing electronic equipment in
power installations.

Now it is important to appreciate that this Declaration of Conformity is for the
inverter only.

On the following page, 122, the manufacturer lists the applicable standards to
comply with the essential requirements of the European Electromagnetic Compatibility
Directive.

In other words, it's an engineer's way of saying "for this equipment to be used
in an installation where it is attached to a motor, these are the applicable
essential requirements".

If you could then please turn to page 123 of 127 in the PDF which has the title "EMI/RFI
POWER LINE FILTERS".

EMI stands for Electromagnetic Interference and RFI stands for Radio Frequency
Interference.

To quote the page -


EN 50081 is the generic emissions standard. For equipment to be sold or
operated within the EU, they must by law meet this standard and a host of
others. Similar standards exist here in Australia.

What the text in this box is saying is "there are some power line filters that you
better use with this inverter to comply with the emissions standards and have less
trouble with other equipment nearby that might otherwise be affected by it".

They talk about the FF Series (Footprint) and FE Series (Standard) filters,
which are separate products they supply.

I refer you to the drawing at the bottom of page 123. They have separate
drawings for the FF Series and FE Series.

I further draw your attention to a few things on these drawings. Notice on both
drawings they have included a symbol for a common-mode choke on the cable
that runs between the inverter and the motor. This is precisely the device I was
recommending in my previous posts. Secondly, note the use of shielded cable
on that same cable. Thirdly, with the top drawing they have the FF Filter sitting
beneath the inverter (i.e. its footprint) but the dashed lines surrounding the
inverter, filter and choke I interpret to be an extra shielded enclosure.
Fourthly. notice that they show the inverter and filter to sit on an extended
metal plate which is to be connected to protective earth. Above the drawings they
have additional notes on the recommended installation instructions for the filters.

On page 124, they list the various model numbers of filters for the various models
of inverters and also have a mechanical drawing.

Finally, what chance you were supplied with one of these suitable filters and
common-mode chokes?

By the way, I noticed the inverter has a large number of parameters that can
be programmed and the front panel gives me the impression that one can
manually control the motor from it. Have you tried removing the cables
that interface the "USB box" to it and manually operated the motor from the
front panel to see if the problem still manifests itself? By pulling those cables,
you also reduce the loop area of one possible common-mode path.

In any case, my having pointed the bone earlier at the inverter-motor connection
dovetails with the manufacturer's own recommendations, but only time will
tell if my intuition was right. In any case, adding the filter, choke and shielded
cable sounds a lots easier than digging that trench.

I hope this advice proves helpful and solves the problem.

Best Regards

Gary Kopff
Mt Kuring-Gai NSW
02 9457 9049

[Paul Haese]

Thanks for the detailed response Gary.

I did not get any chokes or filters.

I have read the manual as you pointed out the sections and I find it odd that Chokes have not been supplied. I will keep the shielded cable. Do I install the shield at the earth point? The extended metal plates are heat sinks. I have earths on these as shown on the drawings.

I will place the shielded cable well away from the mains delivery cables.

Any suggestions as to chokes. The shielded cable needs to be wrapped twice through a ferrite core. What am I looking for here?

I take it the filters are like those you suggested earlier?

[h0ughy]

glad you found it - i really consider the powered USB hubs as only an extension to get the USB past a few meters of cable extension. still recommend running two;)

[Paul Haese]

I found these, just have to find a place locally that will sell these.

[cfranks]

Paul,

Jaycar (in Adelaide) sell the Ferrite Rings and I think the largest is about 35mm ID. They used to sell a split one that you could clamp over an existing cable but it's not listed now.

Charles

[gary]

Hi Paul,

I suspected they hadn't supplied you with the line filter or choke.

On page 11 of 127 in the inverter manual, the lower drawing shows the cover removed
and they indicate a ground terminal. It is hard for me to tell from the line art if
that terminal is on the actual metal chassis of the inverter, but if it is, that is
where you want to connect the shield of the cable that goes from the inverter to
the motor. Use the shortest, fattest piece of cable you can find that allows
for attachment on the terminal and shield. Alternatively, if the cable is longer than you need,
peel back the shield, connect that to the ground terminal and cut short the wires
so that they remain shielded along their entire length.

If you had the inverter installed inside another metal cabinet or enclosure,
what they are suggesting is that the cable shield would terminate at a gland
on the enclosure at the point where the cables pass through into it.

Try and keep the entire cable as short as practical.

For that extended metal plate that you have identified as a heat sink, when you say
"I have earths on these as shown on the drawings", good, but could you please explain
to me exactly what you did there? :)

The ferrite toroid cores come in a range of dimensions. Here is a drawing of
one -
http://www.farnell.com/datasheets/1696282.pdf
This happens to be this one -
http://au.element14.com/wurth-elektronik/74270097/ferrite-core-cylindrical-680-ohm/dp/2082488?Ntt=74270097
I happen to have purchased a couple of these myself in the last two weeks to use for measuring tiny currents.
However, if you search on the Element 14 web site, you should have no problem finding one
with an inner diameter that you think you will get the cable to loop through
a couple of times.

When you wrap the cable through the ferrite twice, if possible, try and keep
the two windings physically spaced apart. This helps reduce interwinding
capacitance, which is a good thing.

The manufacturer suggests placing the ferrite core as close to the inverter as possible.
The ferrite itself is a poor conductor but it has a high magnetic permeability.

What the ferrite does is it will choke common-mode currents passing through
the cable. The ferrite core can saturate so it has an upper limit to how effective
it is, but it will knock several dB of noise off.

Notice that the filter they recommend is on the power line side of the inverter.
They are trying to block noise being conducted back through the mains and into
your other gear.

Best Regards

Gary

[Paul Haese]

Thanks Charles, will take a look.

Gary, the base of the heat sink is the fixing point for the ground or earth cable. The instructions for fixing this are outlined in the Scope Dome manual. It says to fix at that point.

I will get a choke today and fix the tag of the shielded cable to ground point on the inverter. The filter is another question though. I will have to look around for one of those.

Thanks for the help.:)

[gary]

Hi Paul,

Yes, very good. Appreciate that. However, as grounding systems are usually a matter of compromises, could
you please paint me a picture with just a few words as to where specifically
the cable went to reference ground and roughly how long was the cable? For example, did you strap it to
the protective earth (PE) connection on the motor side of the inverter or all
the way to the ScopeDome USB box or to somewhere else? :)



When you Google for the specific model of line filter the manufacturer recommends
you don't get a lot of hits so it will probably coming down to finding another
brand at the right performance/price point.

Your post yesterday whilst I was composing mine gave rise to the possibility of
a power integrity issue.

On the regulated power supply you mentioned that was powering
lots of other things like your cameras, is it a fancier one with a built-in volt
and ammeter or have you happened to measure the typical DC current draw
with a multimeter that the appliances connected to it were drawing?

Normally you would want the regulated power supply to be delivering
a steady steam of power from its own built-in bulk capacitance to ride out
any dips in the mains. In turn, each digital appliance should ideally be powering
itself from its own decoupling capacitors sprinkled across its own circuit board
and those being recharged by the board's own bulk capacitors. But if you
have a lot of thirsty horses drinking from the same shallow watering hole all
at once, it could deplete very quickly and with it your noise margins will
also drop, leaving them more vulnerable to any noise from, in this case,
the inverter-motor pair.

As you will be aware by looking at the inverter user manual, it has a very large
number of parameters that can be programmed and monitored. Some of them can
control attributes such as the acceleration and deceleration ramps.
As at start-up the motor will look like a short circuit and draw the highest current,
there might also be the possibility of re-programming some of the parameters
in the inverter via its front panel to make the inverter/motor pair draw less when
it starts and stops. You can even change the acceleration and deceleration
ramps to S-shaped and so on. In other words, there might be some parameters
that you can change in addition to the other steps you are taking in order
to mitigate the risk that that the inverter/motor disrupts the operation of something
else or induces noise into your imaging.

Once again, hope this is helpful and good luck.

Best Regards

Gary

[icytailmark]

sounds like its either the cables or the hub.try turning off everything and eliminate one device at a time paul. Hope this helps.

[Paul Haese]

Gary, the earth from the main board is screwed into the recess of the inverter where the earthing screw is located. That screw is in direct contact with the heat sink which is supposed to be the earthing point. That cable is about 3 meters long. Then the earth travels back to the power point and back up to the house which is about 25 meters away.

I don't know if the power supply is providing a perfect supply, but that might just be part of the problem. Below is a link to the power supply I bought. http://www.jaycar.com.au/productView.asp?ID=MP3096

The version I have is the 20amp supply.

Today I had a crash of the systems. The ST-I guide camera would not connect, not even the spare and the focusor would not connect either (but that is controlled by the mount hub pro). The main camera though is now connecting, but that has its own USB now. Next step is to go picking off each item until I have it sorted. I'll report back if I find what is going on here. Frustration is nothing compared to what I am feeling at present.

[Bassnut]

I found the STi very unstable on a USB hub, usually wouldnt connect and if it did often droped out minuites later. With its own USB to the PC its fine.

[gary]

Hi Paul,

I have in my mind the first iteration of how the inverter/motor system grounding might
be more ideally engineered and time permitting I will sketch it for you.
This then doesn't mean you should necessarily implement it in the way I suggest. :)
As I mentioned, grounding systems always require compromise somewhere.
However, hopefully it will illustrate some better practices that you can borrow from
if the other remedial steps you are taking still aren't sufficient for reliable
operation of equipment in your observatory.

Take heart that the term "ground" is one of the most misunderstood terms
in electrical engineering. Electrical Engineers working in different disciplines
within a system will use the term "ground" to mean different things.
So confusing it can be that I think if we could turn back time we would
happily purge the word altogether. :lol:

Cartoon attached below attributed to Bruce R. Archambeault, a Distinguished Engineer at IBM.



Pretty hefty, but if you ever get the chance to use your multimeter to measure
the actual current draw of the gear you have connected to it, it might help
eliminate any surprises there.



Sounds like Fred's anecdotal advice with his camera and the hub is good advice
and all you can keep doing is knocking these off one by one. There is always
a chance that more than one thing was going on here and in combination they
were enough to drop the overall system reliability.

Best regards

Gary

[Paul Haese]

Thanks guys, reinitialised everything today and all connected fine. Odd behaviour but imaging runs will tell me what if anything is going to drop out now. All things being equal I hope that this means the system is ok now. Yesterday I did install a heap of drivers again and but I did not fully test things at the end of the day as I wanted to get home. Today all seems fine.

Fred, the ST-I has worked fine for me all along through the hub. I have used it for months on end and never missed a beat, that was what was so annoying. All connected now, so I am expecting no other issues with it now. Perhaps I just did not reboot properly (just a simple restart instead of cold boot). Time will tell of course.

Computer is now running and collecting cloud data so I can revise the cloud sensor settings.

[Paul Haese]

Imaging run tonight. With the roof incorporated into CCDautopilot I get glichy stuff happening. Roof will open and close ok and camera is fine but focusmax might play up or pinpoint will not solve. Odd stuff. Take the dome software out of the equation and things seems smoother. Need to investigate further.

[Marke]

Just a thought but there maybe a port conflict with the dome driver and other software in that when called up its trying to access an assigned port
or address that is being used by something else .

[Paul Haese]

Mark, I looked fairly carefully for any conflicts but it might just be that the original com port assigned to the dome is what the dome software requires. It could be that CCDautopilot is a bit glitchy too. I found it does not finish runs off at all. There is always an issue near the end of the run. Either memory or some other communication issue.

[Marke]

Paul I have found exatly that , some software is picky about the coms port and dont like to change . USB can get randomly assigned different ports when unplugged and replugged . It may just mean plug things in with a certain order , so say the Dome gets first pick of the port maybe ?