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Old 12-07-2018, 10:52 PM
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Stonius (Markus)
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Looming cross-talk questions

Hi there,

Is it okay to loom all types of cable together, no matter what type of signal/voltage/amperage they are carrying?

I'm thinking of dew heaters or fans at 12V PWM with fairly high amps alongside 5V milliam USB signals in the milliamps, especially since I'm thinking of just whipping up a few of my own dew straps.
There's also the temperature probe for the monlite focuser in there too, and I have no idea of the shielding or logic levels employed in that sensor, possible induction, etc.

Has anyone ever had any issues, or does anyone have any knowledge in this area?

Cheers

Markus
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Old 12-07-2018, 11:23 PM
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I have cables for PWM 12V dew heating tapes running next to cables for DS18B20 digital temperature sensors (used under the heating tapes). The PWM can interfere with the sensor reading.
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Old 13-07-2018, 07:39 AM
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multiweb (Marc)
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I've got ferrite blocks on my USB cables and I tend to keep them away from power cables as much as possible, mount power and certainly dew heaters. Ferrite seems to help minimizing noise. As for the rest maybe that's the placebo effect. But I've been doing it for so long I haven't revisited since. More importantly I have opto isolators between any serial connections and USB. I'm statically charged after a few ports on a windy night and I can blue screen a laptop with my mind powers by just touching the aluminium mount leg.
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Old 13-07-2018, 01:34 PM
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ZeroID (Brent)
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I always keep my signal\data cables away from any power DC or AC. I am in an backyard Ob so have AC mains voltages to deal with as well. I run AC and 5/12volts etc up one side of the pier and data and guiding signals up the other. I would certainly NOT bundle all my cables together, it pays to be cautious.
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Old 13-07-2018, 02:06 PM
Imme (Jon)
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I run all power in one loom, all signal (USB cables) in another. They may run next to each other however they are not wrapped up in each other
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Old 13-07-2018, 02:15 PM
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strongmanmike (Michael)
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Just to really confuse you ... I have had all power and USB cables for two CCD cameras, two lodestars, two guide cables, an Atlas focuser and filterwheel, bunched together and routed around the scope and mount for the last 4 years... and no issues My dew heater and mount control cables (USB and Seriel-USB) are not bunched in with these though, they run sperately.

Mike
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Old 13-07-2018, 02:26 PM
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Hehe I'm with Mike. I try to keep them separate but cables and wires tend to be willy nilly to some degree.

I don't see interference from the main imaging camera but have had at times weird lines in the STi autoguider. Not all the time though. It still worked despite the occasional odd looking image.

So yes it would be best practice.

Does it need to be done? No.

Greg.
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Old 13-07-2018, 03:50 PM
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I have the whole lot all bundled except the dewstraps. No issues whatsoever - round stars, perfect guiding, no “frazzle” on downloaded images.
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Old 14-07-2018, 01:52 PM
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Stonius (Markus)
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Quote:
Originally Posted by luka View Post
The PWM can interfere with the sensor reading.
Ah, that makes sense. Have you had any issues (or should I expect any) bundling the sensor cable with USB cables? They're single wire sensors, I believe so not sure how good they are at rejection.

Quote:
Originally Posted by multiweb View Post
I've got ferrite blocks on my USB cables [...] I'm statically charged after a few ports on a windy night and I can blue screen a laptop with my mind powers by just touching the aluminium mount leg.
Maybe I should get me some of those blocks too. BTW, I'm the same. Sometimes I think I'm like a walking EMP. :-/

Quote:
Originally Posted by gregbradley View Post
I don't see interference from the main imaging camera but have had at times weird lines in the STi autoguider.
I'd be suprised if it were possible to have a partial or subtle degradation of the image from cable crosstalk. With checksums and what-not it's not like the analogue realm. The data isn't degraded - either makes it or it doesn't. Wouldn't interference in the serial lines then either be extremely obvious or non-existent?

Thanks for all the input, especially Rally who PM'ed me privately with a wealth of information.

Cheers

Markus
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Old 14-07-2018, 01:56 PM
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Stonius (Markus)
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Just thinking about this, I guess it makes sense to have the power / PWM loom run up the same side of the mount that the motors are on and try to keep the Data loom on the 'clean' side.

That is what I will attempt, anyway :-)

Hoping to get out tonight and have a go at some planets as a test of some new gear configurations.

Thanks all

Markus
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