USB2EQ5 random disconnects

Questions about hardware and software obtained directly from Shoestring Astronomy
Post Reply
Tailspin45
Posts: 2
Joined: Sun May 03, 2020 4:32 pm
Anti-spam question: Astronomy

USB2EQ5 random disconnects

Post by Tailspin45 » Tue May 05, 2020 10:40 am

Having problems driving my SkyWatcher EQM-35 Pro scope directly from Win10 PC using EQMOD and associated drivers with Carte Du Ciel (CdC). I have the latest firmware (4.39.10) installed in the hand controller.

Image

The problem is the scope disconnects at random intervals under no repeatable circumstances.

The mount works fine when controlled just by the hand controller, and it works fine using a USB cable to the hand controller USB Type B port with SynScan PC-Direct enabled. It also works fine with a WiFi dongle.

With electrical engineer John Upton's help (atm-workshop.com) we determined that the disconnects seem to be related to a drop in voltage, which can be as low as 10.5v during a combined RA/DEC slew. The mount's power supply, connect to a home 120v outlet, is producing 12.5v but the mount voltage as reported by the SynScan function is 11.8v at rest, whatever that proves.

The hand controller comes alive as soon as the USB cable is plugged into it, even before the motor control box is turned on, so its clear USB is providing some power. Perhaps that accounts for reliable operation when connected PC-Direct through the hand controller.

Does the USB2EQ5 cable provide any power to the motor control box? Do the symptoms I've described suggest a problem, or better yet, a solution?

dpanderson
Site Admin
Posts: 1053
Joined: Fri Apr 28, 2006 1:34 pm
Location: central Iowa
Contact:

Re: USB2EQ5 random disconnects

Post by dpanderson » Tue May 05, 2020 12:20 pm

I've not heard of any issues like this until now. The USB2EQ5 does not provide any power to the mount.

Given that the mount power supply is 12.5V but the mount is reporting 11.8V at rest, then dropping down to 10.5V during a slew where more current is drawn, I'd suspect something that is creating excessive resistance between supply and mount. Perhaps a marginal wire, imperfect connector, or even an issue with the supply itself. However, you say it works fine with the handcontroller.

Do you see the same behavior in voltage when you use the handcontroller?

If not, then its possible the connection through USB2EQ5/computer is creating a ground loop that is affecting the supply voltage. If you could try a laptop on battery power not connected to anything else except the USB2EQ5, no USB hubs, etc, this would allow the laptop to "float" and should eliminate ground loops.
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

Tailspin45
Posts: 2
Joined: Sun May 03, 2020 4:32 pm
Anti-spam question: Astronomy

Re: USB2EQ5 random disconnects

Post by Tailspin45 » Tue May 05, 2020 2:11 pm

Bingo! We have a winner.

With the laptop connected to 120v via converter rest voltage with USB2EQ5 cable connected was 11.4v. Powered up mount, did 1-star align, slewed to Vega, and switched hand control to voltage indicator. Slewing a single-axis and voltage went to 11.3v on DEC, but during RA slew it stayed at 11.4v. Slew both axes at once and it dropped to 11.2.

A ground loop seems to be the issue. Unplugged the laptop's power supply, powered on the motor control module launched Carte Du Ciel, reset the COM port in EQMOD, and clicked connect.

GOTO slew and sync from Home (±NCP) to M81, then GOTO slew and sync to Vega where I left it tracking while I fixed lunch, then GOTO back to Polaris, then told EQMOD to park the scope. Worked just as should, no disconnects.

So it seems I have a problem with the laptop power converted brick?

dpanderson
Site Admin
Posts: 1053
Joined: Fri Apr 28, 2006 1:34 pm
Location: central Iowa
Contact:

Re: USB2EQ5 random disconnects

Post by dpanderson » Tue May 05, 2020 4:21 pm

Ground loops can be difficult to diagnose. It could be the mount supply, the laptop supply, the wiring in your house, a plug strip if you are using one. The only think I can suggest is trying to replace what you are able to until it goes away. You can try a plug checker to make sure the wiring in your house is done correctly.
https://www.digikey.com/product-detail/ ... ND/6597004
Doug Anderson
Shoestring Astronomy
http://www.ShoestringAstronomy.com

Post Reply