A lesson on why cable management is important

[AstroLearnerWill]

As a relative newbie, my approach to the hobby has been to:

1) take some images

2) realise where an improvement can be made (there are always improvements or something new to do)

3) make the changes / spend money / optimise

4) rinse and repeat

 

I went through such a journey this week and learned why you shouldn't have six cables all sporadically sprawled across an active mount & telescope (HEQ5 + SW 80EM).

(I have three 5m data cables heading to my laptop, three power cables, plus dew heater cables)

A loud bang and a bright flash later I find that the power cable to my Canon coupler had completely blown off.. 

 

Needless to say, I have a Pegasus power box advance on order..

 

[carastro]

Sorry to hear about what happened.  However I have been imaging for 12 years or so now, and the only time I tried to tie my cable up I caused more problem than letting them hang.  One of the cables nearly got pulled out at it's socket.  So I simply tie back the first part of the cables and let the rest hang.  Never had a problem since.

Carole 

[Elbasso]

2 hours ago, AstroLearnerWill said:

As a relative newbie, my approach to the hobby has been to:

1) take some images

2) realise where an improvement can be made (there are always improvements or something new to do)

3) make the changes / spend money / optimise

4) rinse and repeat

 

I went through such a journey this week and learned why you shouldn't have six cables all sporadically sprawled across an active mount & telescope (HEQ5 + SW 80EM).

(I have three 5m data cables heading to my laptop, three power cables, plus dew heater cables)

A loud bang and a bright flash later I find that the power cable to my Canon coupler had completely blown off.. 

 

Needless to say, I have a Pegasus power box advance on order..

 

Dang it. That's not cool.

I also have 5 cables hanging around and expect something to go wrong at some point.... If only myself tripping over the cables in the night when I re-position my mount if my house gets in the way of a new target.

Think the Pegasus is a cool addition to any set-up though. They're just so friggin' expensive.

[AstroLearnerWill]

3 minutes ago, Elbasso said:

If only myself tripping over the cables in the night

Yep, did this too

They're definitely too expensive! As is the norm for this hobby unfortunately..

Nearly everything I've bought for my setup including the pegasus has been second hand from https://astrobuysell.com/uk/, which helps a little. Then you have the expense of all the short cables you need to do it neatly. Still, I'm hoping that it will reduce my setup time somewhat. 

[tomato]

Did the insulation break down and cause a dead short?

I’m not a fan of 240v near a rig for all sorts of reasons.

[Carbon Brush]

Mains on a scope is to be avoided if possible.
Elastictrickery on wet grass and all that.

Don't forget the 'average' cable is intended for use around room temperature.
They become very stiff when cold. Unless you buy low temperature cables, sometimes known as arctic grade.
In this case the outer plastic fractures, exposing the conductors and one twist later BANG.

Another factor is the PVC degrading. Take a brand new cable, and a few years old apparently identical cable.
The old one will have stiffended, especially if exposed to UV, or solvents, or oils.

In the big money pit of astro imaging, new cables every year or two, or better quality cables, are insignificant.
This goes for all the cables. Mains, 12V power, USB, network, etc.

HTH, David.

[AstroLearnerWill]

Ah yes it could possible be related to the cold as it was near 0 celcius when it happened. 

Also, it was definitely a cheap cable that came with the cheap coupler, from Amazon. 

How would one go about avoiding mains on the scope? Say I've got a pegasus advance box on the scope, that reduces all the mains cables to just one, ie the cable powering the advance box. This is a cable / power supply from pegasus so I'd hope that would give a bit more durability. But is even just one cable attached in that fashion avoidable? 

Thanks

[Padraic M]

Wow how did that happen? Looks like a clean cut, but it sounds like it sparked.

The Pegasus PPBAdv is fantastic, you'll never look back. What PSU will you use with it? That should be the only mains near the mount (excluding laptop if you're using one). I use the Nevada Radio 30A PSU powering the PPBAdv and low voltage to everything else from there. The PSU should go in a weather-proof box of some sort.

Some people run low-voltage with a long cable from inside the house to the mount, but that can have other issues like voltage loss in the cable. That can be countered by having slightly higher voltage at source (Nevada is 13.8V) or using a buck/boost converter at the mount to counteract any cable loss and reconstruct the 12V.

[Anne S]

I use an outdoor mains cable which is plugged in via a circuit breaker via an outdoor socket on the wall of the garage. I have a bench power supply connected to it convert it to 12 volt. Hitecastro or Pegasusastro Powerbox mointed on the top of the scope, or somewhere on the mount if available. I'm in an observatory so the bench power supply is protected from damp. It's also on a small table. If I don't have a Powerbox with usb ports I use a 12 volt powered usb hub. I then connect usb to mount wiring or direct to pc. I've got usb2 wired through the mount.

Laptop sits by the scope to control things. I can connect wirelessly to it but I don't often as I need to rotate the dome fairly often as its manual.

My starparty setup has a MINIPC mounted on it so I use wireless to connect and control everything. I plug the extension lead into a mains socket in my motorhome garage. 

Some use batteries when away from home to power everything.

Anne

 

[Carbon Brush]

While thinking about using mains on astro kit.......

Many items (originating in China) have a 13A fuse in the plug. A one size fits all solution. A bit like chicken wire  in a home fuse board🤔.
Always when you buy a lead or equipment check the fuse.
For example ,small items (like the clone Canon coupler) take very little power. Use a 3A or lower fuse.
Always rate the fuse according to the equipment.
A lower value fuse will ensure events like the OP cable failure have a quieter BANG!

Another problem I have seen on some Chinese equipment is fake fuses. Yes FAKE!
The fuse used in our 13A plugs is 1" long.
The fuse wire is NOT taken beyond the ceramic tube and bent over. It is internally fixed.
Those above are two giveaways I have seen on fake fuses.

Another one that you don't see unless you break open the fuse is the filling.
A properly made fuse contains a fine sand to quench the arc when there is a big fault to vapourise the wire - yes it happens.
I have seen fake fuses without the sand, which means the energy transferred under fault is far higher.

When I challenged the equipment manufacturers, they tried to fob me off with what are best described as fairy stories.
As the parts had come from amazon, that was where I went next. amazon withdrew the items from sale.
Though probably a less than scrupulous marketplace seller remarketed a week later under a new name.

Needless to say, anything not bought from a big name with known quality controls is best treated with suspicion.
The amazon marketplace and ebay sellers...........

If in doubt, swap the fuse. A known good fuse purchased from an assured source costs pennies.

HTH, David.
 

[AstroLearnerWill]

On 28/02/2023 at 20:45, Carbon Brush said:

While thinking about using mains on astro kit.......

Many items (originating in China) have a 13A fuse in the plug. A one size fits all solution. A bit like chicken wire  in a home fuse board🤔.
Always when you buy a lead or equipment check the fuse.
For example ,small items (like the clone Canon coupler) take very little power. Use a 3A or lower fuse.
Always rate the fuse according to the equipment.
A lower value fuse will ensure events like the OP cable failure have a quieter BANG!

Another problem I have seen on some Chinese equipment is fake fuses. Yes FAKE!
The fuse used in our 13A plugs is 1" long.
The fuse wire is NOT taken beyond the ceramic tube and bent over. It is internally fixed.
Those above are two giveaways I have seen on fake fuses.

Another one that you don't see unless you break open the fuse is the filling.
A properly made fuse contains a fine sand to quench the arc when there is a big fault to vapourise the wire - yes it happens.
I have seen fake fuses without the sand, which means the energy transferred under fault is far higher.

When I challenged the equipment manufacturers, they tried to fob me off with what are best described as fairy stories.
As the parts had come from amazon, that was where I went next. amazon withdrew the items from sale.
Though probably a less than scrupulous marketplace seller remarketed a week later under a new name.

Needless to say, anything not bought from a big name with known quality controls is best treated with suspicion.
The amazon marketplace and ebay sellers...........

If in doubt, swap the fuse. A known good fuse purchased from an assured source costs pennies.

HTH, David.
 

Thanks @Carbon Brush

Out of interest I broke open the fuse of the offending plug to see what was inside, what do you make of this? Certainly no fine sand, for one. 
 

 

[wulfrun]

Two things immediately obvious: first, it's a 13A and shouldn't be and secondly it doesn't appear to have blown. Meaning, the lead/fault acted as the "fuse". A fuse should always be equal to or lower than the wire-rating of the lead and that's not 13A wire!

I don't recall ever opening up a BS-rated 13A fuse, can't comment if the construction is as expected.

EDIT: it's a common misconception that the fuse is there to protect the appliance. It isn't. The sole purpose of the fuse in the plug is to prevent overload of the wiring. If the appliance requires further protection, fuse(s) should be within the appliance.

Edited March 3 by wulfrun

[Carbon Brush]

Sorry we are drifting a bit off topic. But still near enough. Also it is a safety issue, not a deliberate diversion off subject.

This may be of interest.
https://www.pat-testing-training.net/articles/fuse-operation-characteristics.php

Also this article describing fuse physical size and construction.
http://plugwiring.co.uk/plug-wiring-posts/choosing-the-correct-fuse-for-an-appliance-with-a-bs-1363-type-plug/

I am of the opinion that electrical equipment importers are getting away with far too much poor quality kit that is sold on by retailers who evade responsibility.
We see electrical fires in the UK that are caused by 'faulty' equipment. Actually more like poorly designed and dangerous equipment.
Yes a few end users put chicken wire in fuse holders, make bodgit repairs on mains leads, etc. But they are the minority.
These days most people shy away from anything electrical.

Also not all retailers are irresponsible.
A few years back I was chatting with an electrical engineer who in a former employment had worked for Argos.
His role was head of electrical safety. This included trips overseas (including China) to see the factories as well as liaising with UK trading standards following up fault reports.
Certainly while he was there, the company took electrical safety matters seriously. He told me one or two 'interesting' stories!
These are definitely off topic and for another thread.

I can only repeat my ealier comment. If the lead or equipment are not from a source where you can have confidence safety standards are being met, then swap the fuse.
For example if I bought a fan from Tesco, I would be confident it was 'right'. If it came from an amazon marketplace seller, or an ebay seller.......

HTH, David.

 

 

[Carbon Brush]

Just one two more links.
If you scroll down you can see a non-compliant fuse like that in @AstroLearnerWill plug!

https://www.pat-testing-training.net/articles/counterfeit-plugs.php

This is what happens when they have to earn their keep!

https://www.pat-testing-training.net/articles/fake-fuses.php

Edited March 3 by Carbon Brush
Extra info

[AstroLearnerWill]

Needless to say I will be purchasing an assortment of REAL fuses! Thanks all for the help.. and what an interesting 'edge-case' you come across in the hobby.