Re: Bluetooth and SiTech

Ross Salinger

Since Don W’s last visit we installed RF chokes “all over the place” and also put in a stick computer on the back of the telescope. We eliminated the plastic hubs as well. So, at this point we have a configuration that can be run remotely from anywhere in the observatory and it works. We also have an A/B switch installed near the remaining hub which allows us to switch between the original computer and the stick at the touch of a button. So we now have two computers that can be used interchangeably to drive the mount.


There are more no “call Dan” errors, no encoder errors, no MaximDL freezes, no computer reboots. The stick computer is connected to our “never fails” hub by a 28/24 high quality USB3 cable about 1 foot long. There is a 15 foot USB 2.0 cable of dubious parentage that one of us (Bob) “found” that goes from the remaining “industrial” hub to SiTech, through the mount. The last two nights I’ve been out there we’ve gotten a specific error “Bad Communication” and the mount stops. I’ve been able to clear that error by rebooting the SiTEch box and/or switching computers. Since I’ve gotten it using both computers, and the only thing that they have in common is that cable that Bob found. I conclude that cable is the problem. It even has an RF choke on it at both ends.


Given all that it seems to me that we now have a stable configuration except for this one cable. To me the easy and obvious solution has been to either run a serial cable to SiTEch through the mount or to buy a blue tooth adapter. I personally think that the more USB wiring you have, regardless of quality, the more trouble you will have in an outdoor environment. We have a second configuration in the observatory – a Paramount. It’s longest USB cable is maybe 6 feet long. It has never, in the four months it’s been there, experienced any failures at all. It runs off another Stick computer (or a laptop) located within inches of the mount. I also have a portable setup that I run in my back yard. Same deal – only short cables – longest cable is 6 feet. Again, NO USB problems.


The BT adapter seems really elegant to me. It sounds, though, as if there aren’t many of these in the field so maybe the serial cable is a better idea. My car’s phone seems to work really well J on blue tooth, as do my wife’s headphones. That’s all from me folks.

Happy Holidays.




From: SiTechservo@... [mailto:SiTechservo@...]
Sent: Wednesday, December 21, 2016 12:50 PM
To: SiTechservo@...
Subject: RE: [SiTechservo] Re: Bluetooth and SiTech



Hi Jesse,

When I was using that scope in November to observe Asteroid 169078, everything worked during the heat of the day - including the 4 Startech USB3 hubs.  As we started observing that night the temperature was dropping.  When the temp approached 32°F, three of the Startech hubs quit working - the three plastic housing hubs.  The one Startech metal casing hub continued working fine.  Unfortunately, SiTech was on one of the three that failed.  Adding heat from a hair dryer got that Hub working again - proving that the problem was cold temperature.

I think almost all of the problems you talk about were due to USB cable length and temperature.  Getting the cable lengths to work in day time doesn't guarantee it will work at night - in the cold.

So your solutions are to:

1. Find USB hubs that will work in the cold.
2. Put the hubs in a heated insulated box.
3. Stop using hubs and go with Ethernet or local PC.
4. Use a serial cable to SiTech from the PC, not a USB/hub

Don W

---In SiTechservo@..., <jmgoldba@...> wrote :

I believe initially we started with USB2 and decided to go 3 when we had issues thinking that 3's stricter requirements would ensure better quality at the hardware layer. We also were thinking 3 bandwidth from the computer to the hub would be nice with all the 2 devices (esp. cameras) feeding it.

The most recent discovery was that one of our hubs was seemingly causing errors recently when the temperature dropped close to freezing - so it's been replaced with a more 'industrial' one.

I don't know if we've tried bypassing the hub altogether to get to the SiTech. The stick computer on the mount is a recent addition. Part of the problem is that we can occasionally operate for several hours without issue so performing some of these tests can take some time. We've declared victory before only to face issues on the next trip...


Join to automatically receive all group messages.