1. it doesn't help to just run the laptop off its battery.
2. I have moved the USB-Serial to the hub - thanks Marc!
3. The main problem looks like it was the 550D power supply - although I did not test running the camera on its battery with the USB-serial in its original position (as per pic in original post)
I have ordered 2 usb isolators, one of which I will put in front of the hub, and if I still get problems I will put one between the 550D and the hub.
Some more information I had saved in an old text file:
/////////////////////////////////////////////////////
Ground loops and power supplies are tricky things. Take these steps to find out if you have a possible ground loop.
1. Turn off all power supplies. Leave the power supplies plugged into the house current.
2. Disconnect all power supplies from the Gemini and camera. Leave the one to the computer plugged in.
3. Measure with an ohm meter between the Gemini power pins of the VCD OUT GND pin (see page 131 of L4 manual) on the Gemini to the Ground pin of the Camera and then a ground spot on the Computer. Also measure between the camera and computer. A reading of NO ohms would be perfect. Any low reading could mean you might have a ground loop. This means that the power supply input is not isolated from the power supply output.
4. Next turn all power supplies on. Measure for voltage between the ground outputs to each other. A zero reading is good. anything above 1 volt is bad. Voltage between 0 and 1 volt can also be bad, but depends on how large your wires are. Remember that you are doing this with no/very little current flowing.
5. Reconnect the camera, Gemini and computer. do step 4 with them connected. and see what you have. They should not have changed much. Again voltage between the units is a bad thing.
Computers can cause ground loops because they normally get connected to many other powered devices like monitors, networks and printers through wires.
The best way to eliminate ground loops is to have all the neutral (ground) DC output of every device tied to a central point, through a heavy (12 Gauge) wire. The central point when using a Gemini would be the Gemini ground input pins. This is not easy to alway do. The next best is opto or magnetic isolated inputs to the Guider and RS232 inputs.
If you do do a central ground between your devices, consider puting in a ground rod at least 8 ft deep next to the central point into the ground. This can help prevent static damage.
The best preventive is to use Isolated RS232 or USB adapters and Guiders into the Gemini. They can eliminate ground loops. I use one on all inputs to my Gemini. Of course I manufactured my own.
One word on note: The Gemini's with the slide switch for power do not have the electronics grounded to the case. The Gemini's with the Toggle switch do have the electronics grounded to the case.
//////////////////////////////////////////////////
Some more information I had saved in an old text file:
/////////////////////////////////////////////////////
Ground loops and power supplies are tricky things. Take these steps to find out if you have a possible ground loop.
1. Turn off all power supplies. Leave the power supplies plugged into the house current.
2. Disconnect all power supplies from the Gemini and camera. Leave the one to the computer plugged in.
3. Measure with an ohm meter between the Gemini power pins of the VCD OUT GND pin (see page 131 of L4 manual) on the Gemini to the Ground pin of the Camera and then a ground spot on the Computer. Also measure between the camera and computer.
Any chance you might know where I can find GND on the 550D? What about the netbook - are there any obvious ground points on USB ports or monitor outputs?
Quote:
A reading of NO ohms would be perfect. Any low reading could mean you might have a ground loop.
Do you mean no resistance, or very high resistance. No resistance will mean the current will flow very easily - or is that what you want to stop differences in potential? I am so not an electrician...
Quote:
This means that the power supply input is not isolated from the power supply output.
4. Next turn all power supplies on. Measure for voltage between the ground outputs to each other. A zero reading is good. anything above 1 volt is bad. Voltage between 0 and 1 volt can also be bad, but depends on how large your wires are. Remember that you are doing this with no/very little current flowing.
I guess this would be DC voltage?? I don't want to upset my multimeter...
Quote:
5. Reconnect the camera, Gemini and computer. do step 4 with them connected. and see what you have. They should not have changed much. Again voltage between the units is a bad thing.
Computers can cause ground loops because they normally get connected to many other powered devices like monitors, networks and printers through wires.
The best way to eliminate ground loops is to have all the neutral (ground) DC output of every device tied to a central point, through a heavy (12 Gauge) wire. The central point when using a Gemini would be the Gemini ground input pins. This is not easy to alway do. The next best is opto or magnetic isolated inputs to the Guider and RS232 inputs.
If you do do a central ground between your devices, consider puting in a ground rod at least 8 ft deep next to the central point into the ground. This can help prevent static damage.
The best preventive is to use Isolated RS232 or USB adapters and Guiders into the Gemini. They can eliminate ground loops. I use one on all inputs to my Gemini. Of course I manufactured my own.
One word on note: The Gemini's with the slide switch for power do not have the electronics grounded to the case. The Gemini's with the Toggle switch do have the electronics grounded to the case.
//////////////////////////////////////////////////
Thanks for the info Marc. Will try to find out some more info and give it a go.
Any chance you might know where I can find GND on the 550D? What about the netbook - are there any obvious ground points on USB ports or monitor outputs?
Here's some info on USB wiring. No idea on the 550D.
Quote:
Originally Posted by adman
Do you mean no resistance, or very high resistance. No resistance will mean the current will flow very easily - or is that what you want to stop differences in potential? I am so not an electrician...
Very low resitance to no resistance. It's very unlikely you'd get no resistance at all though.
I have been using a G11 and lots of other bits like you and have only ever had problems with the USB to seal adapters. I have tried quite a few with very spasmodic results. The only way I have been able to eliminate all my problems was to firstly get the Qhy5 off the hub and on a single USB connection and secondly get the Gemini connected to a true RS232 connection and everything worked. My observatory rotation also posed problems with the USB to serial adapter and a swap to rs232 fixed that as well.
thanks Doug - when you use the QHY5, do you have the guide cable connected to the gemini, or do you just have a USB cable connected?
Adam
Adam, I have the guide cable connected to the St4 port on the Gemini and the USB cable connected to the laptop.
We did find there can be a lot of timing issues using USB to serial adapters where they didn't report back to the Gemini or laptop with stop bits and effectively just disconnected USB items at random.
At times either the little LED on the Gemini hand controller would just go off while the gemini power led kept running. This was the Gemini disconnected and likewise the qhy5 would do similar.
Hi Adam did your USB isolators arrive yet? Did they fix your problems?
I am having very similar issues here with a G11G (new type - rocker switch and round motor connections) and a similar setup.
In my case I have the G11G powered buy a Jaycar 13.8V regulated PS, that also provides power to the dew heaters and my moonlite stepper focus controller.
Also running off the same mains socket are a PS for a powered usb hub and the camera power supply.
The laptop connects to the G11G via the usb hub and then a Belkin usb to serial converter, the camera and focus controller are also connected to the hub.
What I found was USB timeouts when image downloads were in progress. I thought to fix that with a second USB cable direct to the camra but when I made the connection at the laptop I got a spark from the USB shield. That stopped me in my tracks!
I measured a 24.7 V poterntial difference between the usb shields on the camera usb cable and devices connected to the Jaycar PS.
I think I can avaid this issue if I swap the ST2k power supply for the DC version and run everything of the Jaycar PS but I am reluctant to experiment for fear of blowing up something expensive. So far I only seem to have fried the USB hub.
Do you really expect anyone to venture an answer knowing that no matter their answer, you could potentially fry your camera? Who wants to be involved with such a disaster? Not me!
Hi Adam did your USB isolators arrive yet? Did they fix your problems?
I am having very similar issues here with a G11G (new type - rocker switch and round motor connections) and a similar setup.
In my case I have the G11G powered buy a Jaycar 13.8V regulated PS, that also provides power to the dew heaters and my moonlite stepper focus controller.
Also running off the same mains socket are a PS for a powered usb hub and the camera power supply.
The laptop connects to the G11G via the usb hub and then a Belkin usb to serial converter, the camera and focus controller are also connected to the hub.
What I found was USB timeouts when image downloads were in progress. I thought to fix that with a second USB cable direct to the camra but when I made the connection at the laptop I got a spark from the USB shield. That stopped me in my tracks!
I measured a 24.7 V poterntial difference between the usb shields on the camera usb cable and devices connected to the Jaycar PS.
I think I can avaid this issue if I swap the ST2k power supply for the DC version and run everything of the Jaycar PS but I am reluctant to experiment for fear of blowing up something expensive. So far I only seem to have fried the USB hub.
Can anyone confirm if this idea is sound?
Regards
I also have a G11 with Gemini 2 and i run everything from one power supply and have no problems at all.
I made a power supply box that is fitted to the telescope and has 8 x 13.8 volt outputs and 1 x 5 volt for usb and 1 x 8.4 volt for my Canon 10D.
My power supply is a 13.8 volt 12 Amp switch mode like the one from Jaycar.
Also why are you running usb to the G2? Lan is much faster now the new firmware has been posted to the general public and it wont hog up precious usb bandwidth.
Hooked up to the box are 3 dew heaters, QHY9m with filterwheel, G2 and my Canon 10D.
One power supply means no ground loop and having everything insulated helps too
I have this setup now for over 2 years and have had no problems at all.
Thanks that gives me hope ! I may have confused you it is not a G2 but a G11 mount with a Gemini v1 controller.
Quote:
Originally Posted by mill
I also have a G11 with Gemini 2 and i run everything from one power supply and have no problems at all.
I made a power supply box that is fitted to the telescope and has 8 x 13.8 volt outputs and 1 x 5 volt for usb and 1 x 8.4 volt for my Canon 10D.
My power supply is a 13.8 volt 12 Amp switch mode like the one from Jaycar.
Also why are you running usb to the G2? Lan is much faster now the new firmware has been posted to the general public and it wont hog up precious usb bandwidth.
Hooked up to the box are 3 dew heaters, QHY9m with filterwheel, G2 and my Canon 10D.
One power supply means no ground loop and having everything insulated helps too
I have this setup now for over 2 years and have had no problems at all.
Do you really expect anyone to venture an answer knowing that no matter their answer, you could potentially fry your camera? Who wants to be involved with such a disaster? Not me!
Hehe the G2 works flawlessly now and we will have loads of features later
Just joking, i know that the G1 is working well
The G2 will have more options because of all the feature ports build in.
Hi Adam did your USB isolators arrive yet? Did they fix your problems?
I am having very similar issues here with a G11G (new type - rocker switch and round motor connections) and a similar setup.
In my case I have the G11G powered buy a Jaycar 13.8V regulated PS, that also provides power to the dew heaters and my moonlite stepper focus controller.
Also running off the same mains socket are a PS for a powered usb hub and the camera power supply.
The laptop connects to the G11G via the usb hub and then a Belkin usb to serial converter, the camera and focus controller are also connected to the hub.
What I found was USB timeouts when image downloads were in progress. I thought to fix that with a second USB cable direct to the camra but when I made the connection at the laptop I got a spark from the USB shield. That stopped me in my tracks!
I measured a 24.7 V poterntial difference between the usb shields on the camera usb cable and devices connected to the Jaycar PS.
I think I can avaid this issue if I swap the ST2k power supply for the DC version and run everything of the Jaycar PS but I am reluctant to experiment for fear of blowing up something expensive. So far I only seem to have fried the USB hub.
Can anyone confirm if this idea is sound?
Regards
Hi John - yes my isolators did arrive, but I wasn't very happy with them. For a start they only ran at USB 1.1 speeds - not great. Then secondly I was still getting problems even with them connected. By trial and error I was able to localise the problem to the dodgy eBay power supply for the 550D. If I ran the camera off its battery, I had no problems.
So my solution was to buy a DC-DC converter from Andrews Communications that gives me the correct voltage for the Canon, and use the dummy battery from the dodgy power supply. Then it was snip-snip solder-solder and hey presto I can now run my 550D off my 45 amp hour AGM deep cycle battery - should last several days before needing recharge. Not the most elegant solution - I would like to have been able to solve it with my setup as it was (now I have to lug said battery with me on field trips...) but I am no electronics whiz by a long shot, and so took the path of least resistance (pardon the pun)
My theory is that if I paid the big bucks for a genuine canon power supply, I wouldn't have had any problems...maybe?
I am now powering all my equipment from a single DC source (except the latop) and that seems to have cured the problem but I have another with my guide cable. I will make a new post for that though.
