Tak EM200 and GPUSB issues

Questions about hardware and software obtained directly from Shoestring Astronomy
Post Reply
dharvey
Posts: 2
Joined: Tue Nov 02, 2010 8:50 pm
Anti-spam question: Astronomy

Tak EM200 and GPUSB issues

Post by dharvey » Wed Nov 03, 2010 1:17 pm

Doug et. al.

I recently purchased the appropriate parts for a Tak->GPUSB system for my first generation EM200 (no goto but it does have a guide port 6 pin PS2 connector). Note - I have done all of the GPUSB checks and your hardware works as advertised with PHD Guide up to the mount. However I see no motion at all when using either PHD or GPUSBCheck. I know the outputs are open collector and it may be that they are not sinking enough current to activate my mounts electronics. I have no schematics for the EM200 electronics but fear that it may need relays instead of the open collector outputs the GPUSB provides. I'm prepared to implement the relay circuit you have in the site documentation on handcontroller modification but want to know a couple of things before I make the effort. What is the difference (electrically at the outputs) between the GPUSB and the GPUSB-AH. Secondly - is there a resistor between the emitter and ground of the GPUSB transistor on the open collector output? If so - what is the value of this resistor in both the GPUSB and GPUSB-AH?

Thanks in advance.

Dave Harvey

dharvey
Posts: 2
Joined: Tue Nov 02, 2010 8:50 pm
Anti-spam question: Astronomy

Re: Tak EM200 and GPUSB issues

Post by dharvey » Thu Nov 04, 2010 11:23 pm

Thanks for the silence. You got my money. That's all that counts I guess. I'll remember the great customer service when I review your product. :roll:

dpanderson
Site Admin
Posts: 1047
Joined: Fri Apr 28, 2006 1:34 pm
Location: central Iowa
Contact:

Re: Tak EM200 and GPUSB issues

Post by dpanderson » Tue Nov 09, 2010 4:36 pm

Dave,

My apologies for not responding earlier. The forum is supposed to automatically send an email to me when a new post is made so that I can respond. However, it seems that for the past few months this has not happened consistently. Knowing that there is this weakness in the forum, I'll try to be more diligent at checking it manually rather than relying on the automatic notifications in the future.

The GPUSB uses open-collector NPN optocouplers to actively pull the outputs down to the common (mount ground) pin 2 when activated. There is no resistor, the emitter is connected directly to the common pin. The collectors should be able to sink at least 45mA of current if needed.

The GPUSB-AH uses open-collector PNP optocouplers to actively pull the outputs up to the mount's positive supply (also connected to pin 2 in this case) when activated. They too should be able to source 45mA, and there is no resistor in the emitter path.

I hope this helps you. Should I not respond on the forum in the future, you are always welcome to send an email to doug@shoestringastronomy.com to get my attention.

Thanks,
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

Post Reply