G11 - Gemini [old box version] - GPUSB-AH or QHY5 guider output?

[multiweb]

I'm revisiting the way I've been doing my auto-guiding. It worked well for me so far but I'm looking at possibly more efficient ways to do it and minimise all the cables hanging off my scope.

At the moment I use a QHY5 [Q-guider] plugged into a USB hub (x4) to the laptop USB2.0 port. I run PHD with the Ascom Gemini drivers. From PHD the guide ouput goes throught the same USB port back to the USB hub then from USB to serial then to a custom made cable serial to RJ11 into the RS-232 port on the Gemini. This works well but still I noticed tracking goes a bit wacky when I use the same USB pipe while downloading the pictures from the camera to the laptop.

I also have a GPUSB-AH which I have tried in a similar fashion with a straight RJ12 cable to the auto-guider port on the gemini. I haven't tested this on the field but on a bench DEC and RA motors respond to the pulses sent so I assume it'll work for tracking.

What I would like to do is plug the QHY5 guide ouput right into the gemini auto-guider port. So far I have crimped one end of the cable, tested and I have approx. 5V on both pin1 and pin2 of the cable right out of the Gemini auto-guider port. As per wiring diagram my understanding is that pin2 is the common ground. Pin1 [usually not connected] may be the power pin in some mounts. Sounds like it is in mine. But I also get 5V on pin2 so that's what made me a bit nervous. :shrug:

Anyone wired an old gemini box to a QHY5 in a similar fashion? What did you do with Pin1 and Pin2?

Most importantly is there any real advantage or performance gain in using the QHY5 guider output?

I read a few threads on this forum so I'm pretty sure some of you are already doing it but I couldn't find any definite wiring diagram.
Thanks for any hints.

[gbeal]

Can't help with the pin outs and all that techie stuff, mainly cos I am a klux with electrics.
If it helps though, I plug my QHY5 directly into my AP400 auto-guider port.
Gary

[rsbfoto]

Hi Marc,

PIN 1 is not used. You got 5v because the PIN2 is the common or ground and PIN1 carries voltage for a different purpose which has not yet been specified.

PIN 3,4,5 and 6 are the guiding pins. Take a look into the Gemini Instruction manual located here

http://www.docgoerlich.de/manL3V11/GeminiUserManual.pdf page 92

There is one thing that the voltage of the old Gemini GoTo control box is a negative voltage and not a positive voltage like in the new Gemini GoTo box.

Pin 2 is the common and the pins 3,4,5 and 6 carry -5v when measured against common = PIN2

I do not know how the output of the QHY8 is but you should be carefull not to fry anything.

The best thing is to use the GPUSB-AH you have.

[Gama]

This has been discussed here on this site some time ago, I think Fahim (Netwolf) had a similar issue.

The pinouts for the camera is on this image for you to look at.
From memory, the QHY-5 i think may have needed a resisitor change internally, which was done at the factory, as the old version worked by electrical switching, and the current mounts work on optical switching. But i may need to check. Maybe some one else with the same mount may shed some light.

Theo

[Tandum]

Like this ?

[multiweb]

I think you're right Rainer - not worth taking any risk by being too "creative". I'll use the GPUSB-AH from now on for guiding as it seems to work. That will free the RS232 port for the Gemini alone [Application on the laptop ] and I can use ASCOM POTH if I need to connect cartes du ciel or other planetarium utilities.

I read a few of your posts in the past and you mentioned you guide through the RS-232 on the Gemini. I do that too but the difference is that my laptop doesn't have a serial port, so I use a USB port then convert to serial with a cable.

The only thing I am a bit paranoid about is ground loop currents. Now I'm going to have a QHY8 in the circuit connected via USB in the circuit I'm a bit nervous, that's what prompted me to change my cables and the way I do the wiring. I heard and read in the past horrible things with SBIG STL11K having fused relays etc... because of similar voltage difference problems.

I'll post or PM a schematic of my setup with the mount/gemini and all my power sources when done so you can have a peek at it and let me know if you see any obvious flaw or potential problem.

Thanks for your help so far. Much appreciated.

[multiweb]

Hi Robin, that looks like a straight cable. You're using this directly between your Q-Guider and the autoguider port on the Gemini? Is your Gemini box the one with the square RJ45 plugs or the round DINs?

[multiweb]

Hi Theo, I got the QHY5 from you back in February I think. Would that be the old version of the factory modified version?

[Gama]

The earlier ones (QHY-5) where the first initial release. Since then they have been using the resistor change.
There should be a post on it on the QHY forum somewhere.

When i meant the "Old version worked by electrical switching" i was referring to the Gemini, and not the QHY-5.
The QHY-5 is and has always been optically isolated.

Theo.

[rsbfoto]

Mi Marc,

That is correct but lately I do all my guiding via the Autoguider port as, as you say, it frees up the RS232 port and that made me forget the ASCOM platform and gives me less trouble.

At the endeffect you only need to guide and a planetarium program connected to the Gemini GoTo in order to use the mount.

I am still guiding with the old parallel port and a Shoestring GPINT-PT adapter. I also have a GPUSB adapter as well as a GPUSB-AH and a GPINT-PTAH adapter.

All of Doug Andersons adapters do work flawless.

[multiweb]

Here's my set-up. Red is power, green is data connections [USB, serial]
Does this look alright or is there any possibility of ground loop currents anywhere?

Laptop is Toshiba Satellite [runs on 19V with an inverter]
Both power tanks are Celestron 12V [17Ah]

[rsbfoto]

Hi Marc,

Can you not connect both tanks in parallel and so you get a common ground for all ?

2x 17Ah is equal 1x 34Ah and you are certain that all goes down at the same time.

You are drawing from one tank far more power then from the other. The biggest consumer is your LapTop and that will make stop the Gemini and your Laptop first and the camera would continue to work. Makes no sense :D

You talk about inverter. Do you mean you step up first to AC current (¿110v or 220v' I do not know what AC current you have down there :) ) and then you step down again just because of your LapTop ? You are just killing Ah

You can get step up DC-DC converters for less then US $ 40.00 like this one

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=2737

I have one working for my Gemini as I feed it with 18volt.

There is a lot of possibilities to improve your power supply and simplify it ...

[multiweb]

Hi Rainer thanks for the link. Yeah sorry for the confusion, that's what I actually use at the moment. It's not an inverter, it's a DC to DC converter for the laptop. I don't know what I was thinking about when I typed that. It's 12V DC in 19V DC out for the laptop. My laptop draws 3.5Ah maximum.

I currently get a good 6 hours imaging out of my setup.

I can't connect both tanks together unfortunately. They're the Celestron power tanks. All closed. No access to the battery terminals. Later on I'm thinking of replacing them by one big Battery. Got a couple of friends who use 100Ah batteries on the field. They're not that big either. Just heavy.

Would you know how much the Gemini draws? I also saw in a post very recently that it's bad to run the motors on 12V DC. It should be closer to 14V DC. They overheat. Is this correct? I though it's all good as long as you correctly balance the load. Mine are the high torque motors and I never had any overheating problems to date.

[rsbfoto]

Hi Marc,

Ah ok that is good that you do not steip up and then down.

The Gemini runs OK from 12volt to 18volt. Overheating is always a result of unbalance.

With a higher voltage you get a higher torque in the motors.

The Gemini draws about 3amp when you slew with both motors at the same time at maybe 1200x to 1400x.

At tracking I guess it does not draw more then 750mamp if I remember well when I measured it once.

Well about connecting in parallel the both tanks there is a way as you have an output on both but if you do not feel safe doing it ...